ads, for Mr. Pratt might equally argue that if it be the same Mercury, Venus, &c.," the influence should the same over the whole solar envelope, as objected should be with respect to our own globe. Well, we ly know that it is not so, and when we know the ason of the amomaly, we shall have an answer to the lanaging query," with respect to the influence of the nets on the weather. Lastly, if Mr. Pratt pledged himself to "thunder and I can only briefly touch upon the letter of Mr. icted. I have the diagram of the whole month before me, nd I must say that it furnishes one of the most rearkable evidences of almost exact science that I have ver examined. ALBERT P. HOLDEN, and the north-east winds, principally by the result of of any cathedral or mausoleum whatever; but he does not, therefore, mean that we should infer the builders had these coincidences in view, but rather that there is nothing unusual about the pyramidal coincidences. From the professor's examples I was led, out of pure curiosity, to try my hand on the great pyramid itself, and the result was the following hitherto unnoticed coincidence. The sum of the twelve profile lines = (earth's polar axis) 5,000. This little numerical trick was thus accomplished: I arranged the various measures of the great pyramid's base as below: 9,163 inches. 9,168 9,162 Colonel Howard Vyse, north side 9,130 Mr. Pratt's explanation of the extraordinary fact that the barometric curve is "raised or depressed indiscriminately" under his "positions" and transition points is quite in the spirit of the rule abuse the plaintiff's attorney when you have no defence." Mr. Pratt observes that "it is important to note now that each planet, while exerting precisely the same force, yet produces different barometrical or thermometrical effects." But he omits to tell us why Neptune should exert the same force as Jupiter, and what the planetary influence upon the thermometer is in their case. Mars, we are told, influences evaporation, yet Mr. Pratt is so ignorant on this subject as to ascribe the formation of ice on a pavement cooled below freezing point, although the air was above it at 37°, to evaporation, and styles this common occurrence, even when raining after a hard frost, a singular phenomenon! We look in vain for any guide to the weather for the next three days, although he cannot find terms sufficiently strong to denounce the present system of storm warnings. The planets blow hot and cold, and produce sometimes contrary effects. How is the captain of a vessel in the Channel to know the "leading weather and the instrumental readings upon the coast so as to correct the "curvature" and "position"? Will Mr. Pratt explain in what way a planet like Mars can produce a high temperature, and why he attributes a hard frost in this country to evaporation, when every ploughman knows that it is the consequence of a N.E., and therefore of a Polar, wind? Still, to students of meteorology his papers are valuable as proving how necessary it is to possess a knowledge of the rudiments of the science before attempting to instruct others. We do not want to know what the weather will be next month, but what it will be during the next week, wet, dry, or windy, day by day. Let Mr. Pratt tell us this, deed. If Mr. Pratt's forecasts are so correct, it was week by week, and we will bail him a benefactor ininhuman on his part not to send warnings of the terrible gale which blew last night (the 10th). Will he favour us with the names of the places where the rainfall amounted to 5ft. 11in., and an explanation of the phrase "force of rainfall ?" It is not easy to see what days are not influenced if we are to except "days of position," of "combined position," and "transition periods." Mr. Pratt has us all ways, high barometer, low barometer, hot planets, cold planets, fast or slow planets, their action or re-action, atmospheres de-years since I saw them, I will only give the notes I and exposed thereby "to the full force" of the attracprived of electricity and of humidity, by one planet, tion of another! I conclude with a quotation: "Parturiunt montes, nascitur ridiculus mus." M. PARIS. GAS FROM PARAFFINE OR PETROLEUM. [1422] ALTHOUGH abler correspondents have ex- 44 And this leads me to the consideration of Mr. Pratt's second error, which is shared by so many weather wise persons, and which has been noted by F.R.A.S." It is in looking for the causes of the weather within The weather of England, for instance, is in the main determined by the south-west too narrow limits. In the United States, a friend of mine once met with It would seem that in country places, where gas is Mr. Hains, in his letter 1938, p. 473, which led me to offer these remarks, asks how far 7 sin. 26° 40′ agrees, beyond the 5th decimal, with . I find the discordance to be 2 in the 7th figure of the logarithm. O. N. REMARKABLE RAINBOWS. [1425] I HAVE read with great interest the letters of Mr. Waters and "E. L. G." (lets. 1278 and 1379), and while they are fresh in the memories of your readers I will mention two phenomena which I witnessed in Cornwall. As it is now more than 20 made at the time. omnibus from Plymouth to Redruth, I observed a phe1851, January 24th.-While riding on the top of an nomenon which I described as a stationary rainbow. Rain beginning to fall, an imperfect rainbow was produced; one half of the bow only was seen, the foot of the arch resting on a hill to which the omnibus was approaching, and passed over, to a considerable extent, a field on which some cattle were grazing. As the omnibus approached the field in question, the rainbow appeared to shift its position but not to recede from the observer: it approached the right hand, the observer facing it by about 50 yards. As we neared the field in which it was seen we came nearer to it, and it certainly did not in any degree appear in any way to recede, but was, with the exception alluded to, perfectly stationary, and it thus continued until we arrived even with the field, when we saw it at our side, immediately upon which it disappeared. On my return journey from Redruth to Plymouth, 1851, February 1st, I observed the segment of a rainbow; the direction in which the omnibus was moving was such that the rainbow was on the left and the sun on the right hand, the omnibus moving towards the east. In this instance the observer was certainly not between the centres of the sun and arch of the rainbow,he sat opposite the eastern extremity of the coloured arch, and as the omnibus moved the rainbow also appeared to move along the country towards the east, the omnibus gaining upon the rainbow, so that it ultimately became opposite the very extremity of the arch. I do not now recollect whether the shadow of the omnibus fell towards the centre or towards the extremity of the arch; this is important, as it would tend greatly to solve the nature of the phenomenon. It is evident the rainbow was not produced in the ordinary manner from its ellipticity, and the position of the observer relative to it; the motion of the bow to a certain extent being coincident with that of the omnibus, is in accordance with the view that each observer sees his own rainbow, but the omnibus gaining on the bow.` [I am unable to proceed further, as the record terminates here.] W. R. BIRT. THE LUNULE OF HIPPOCRATES. [1426] THE exercise Mr. Toukes says he has never seen published' (letter 1839, p. 474), was originated by Hippocrates, of Chio, one of the most ancient geometers of Greece. It has been published in several books under the name of "Lunula of Hippocrates," and is easily proved by the properties of the right-sided triangles. Vide Dictionary of Mathematics," "Geometry of Lege ndre," &c. ANTIQUARIAN. PIANOFORTE IMPROVEMENTS. [1427] I AM sorry that I have not had time to reply before to the "H. B.," but I beg to inform him that I have not made an instrument with the four strings, on account of the expense attached to the action, but I have commenced a pair of backs, with the third string an octave lower. His objection to the striking distance of the long string I get over by putting an extra bridge upon the plank, so as to make striking points the same. I know that it requires a first-class bellyman, and one that is well up in his work, to carry it out; and I hope, when it is finished, that he will be able to give the readers of the ENGLISH MECHANIC his opinion after an inspection. JAMES JENKENSON. ODIC FORCE, ETC. [1428] "SIGMA " having kindly answered my question (6212), may I beg of him a few words more on the last part of his reply? I have not the slightest wish to raise a discussion on the subject of tableturning, but wish to obtain a few earnest remarks upon a matter which usually meets only with ridicule. "Sigma's" opinion is, that the movement is "the result purely of mechanical impulse," given unconsciously by the actors. This is the explanation generally given, and was that of Faraday and the French Academy, the former of whom was considered to have thoroughly proved its correctness by his little rolling instrument. But this was some time ago, and I would ask " Sigma" whether, in the face of such works as those of Reichenbach, it is possible to hold the theory a moment longer. Remembering that he writes in 1867; that he is well known, and is by no means looked upon as a "humbug;" that his works contain numerous carefully conducted experiments related with preciseness, in short, that from beginning to end they bear the aspect of truth, what are we to say to such an experiment as that given in page 109 of his "Odische Lohe," and which I repeat in a few words? On the circumference of a table, Sft. across, were scooped eight hollows, into which were loosely fitted pieces of old limp cord, hanging down some 12in. They fitted exactly and were merely tucked in; the slightest pull causing detachment. Six persons now held the cord ends (some two, some one), and in three-quarters of an hour the table was in full motion; not a cord having been pulled, nor the table touched." Further on is an account of a soirée at Lord William Cowper's, in '61. On this occasion Reichenbach got under the large oval table,which had one central shaft on three legs; he laid his body across ene and clutched the others, determined to prevent any movement. By using considerable force he got mastery over the first few jerks, but the table suddenly starting off with a violent Inrch he was dragged across the room, to the intense laughter of the company (and, I should say, to his own great personal discomfort; for, accustomed as he must have been to see other people look foolish" on such occasions, this was a case of the "table's turning" on him with a vengeance). Now "Sigma" surely cannot say that in the first case "mechanical" impulse was at work, seeing this was absolutely impossible; nor, in the second, is it credible that mechanical impulse of the kind in question, assuming it to be given, should prove strong enough to rudely overcome the weight and force of a full-grown man. There seem to me then only two ways of thinking left, we must either simply decline to believe in the veracity of the experimenter after, say, page 108 of this book, or we must accept Reichenbach's simple, consistent, scientific, and, to my mind, amply proved explanation of the phenomena of table turning. Sigma "see any objections to the adoption of the latter belief, I trust he may not consider it waste of time to express it. But if experiments ever proved anything, the two here given, ont of many more, certainly do prove that the old explanation can Should stand no longer. A. C. G. which will have do thermal effect, and if so, is the fact not due to the impossibility of finding a source of light which doos not at the same time throw out heat, and not being a mathematical point, afford us a mixture of luminous and calorific rays? If we take the case of a fixed star we have considerable light, but, as far as I know, no heat. We have rays of heat which produce no light, and therefore why not light rays devoid of calorific power? The question of "S. P." seems to me to be this, Does a ray of heat, by change in rapidity of vibration or otherwise, cease to produce calorific effect when it produces light; or, in other If so, it is cerwords, is light merely visible heat? tainly curious that the hottest part of the spectrum should possess no luminous properties. Is it not true that by no device can we obtain a single pure colour in the spectrum, that there always is a mixture throughout of all rays more or less? M. PARIS. [1430] MOUNTING IN CARBOLIC ACID. CARBOLIC acid has not, I believe, received much attention as a preservative fluid for microscopic objects, which, from its powerful detergent properties, I think it merits. Possibly this occurs from want of introduction. In most cases I have used it I find it answers very well indeed, especially amongst vegetable preparations; in fact, it will not do for all animal tissues, because it immediately coagulates the albumen to an extent rendering them in many instances nearly opaque; but even amongst these in some cases I find it possesses the peculiar property of bringing out the cell wall and nuclei, that in all other liquids I have tried, except acetic acid, were invisible. I first observed this in the deep layer of the epidermis and tactile papilla of the tongue of the white mouse, a very thin section of which I obtained from Mr. White, of Monmouth. How far this property may be the case as a general rule I am unable to say from want of experience; but in this case I see it possesses an advantage over acetic acid, insomuch that acetic acid by dissolving the albumen alters to a considerable extent the natural appearance of the preparation, whereas this is not in the slightest One thing is very degree the case with carbolic acid. necessary to be thought of in using it to see this effect, and that is, the sections must be very thin and clean cut. I use a solution of one part Calvert's pure acid to twenty parts of distilled water. A small quantity of glycerine must be added to the acid first, in order to render it soluble in the water. A weaker solution than this would perhaps be sufficient to prevent decomposition if thought advisable; but for vegetable preparations a strong solution is not objectionable. I hope to see more information on this subject from of your numerous correspondents, who are better able by their experience than myself to write about it. some CANADA BALSAM. P. H. W. (1481) MUCH controversy has taken place of late with regard to warming thick balsam. As far as my own experience goes, I thoroughly endorse the opinions set forth by Mr. White; it is perfectly easy to obtain new balsam, and its cost is very little considering the quantity used. I certainly cannot understand why persons should trouble themselves in trying all sorts of plans for thinning balsam when fresh may be obtained at so little cost, and in a much more uniform condition; and not only this, but balsam thinned with chloroform will form a film from its volatile nature so much sooner than the genuine article, and thus cause an immense deal of trouble and annoyance in the imprisonment of air bubbles, a fact, I think, of which all must be well aware who are in the habit of using it. I find no difficulty in hardening thin balsam after mounting; animal tissues are developed in the human body at a temperature of 100° Fahr. In birds, 110° Fahr. and most vegetable tissues will certainly stand 80° or 90° without injury; and this temperature, or even less, is quite sufficient to harden the thinnest balsam in a moderate amount of time. I will give experiences of Mr. White's new media as soon as he has introduced it to microscopists. From the principle aimed at, I anticipate its being a boon to microscopists, as his prepared objects are. And with regard to these, I feel it a duty to Mr. White to say that from him I have obtained objects that no amount of time or money would obtain for me elsewhere. I find, to cut half a dozen different wood sections, or prepare half a dozen different silicious cuticles, takes up a good deal of valuable time, and as I can get them from this source for 1d. each, I imagine I save time, or rather with me it means money, by the transaction. Until very recently I had not been in the habit of seeing the ENGLISH MECHANIC, and was most agreeably surprised to find it contained so much and so good scientific matter. I have read with much benefit most of the microscopic articles, especially those of "H. P. H." P. H. W. ON LIGHT AND HEAT. [1429] I HOPE the interesting question raised by HYDRAULIC RAM (LET. 641). "S. P." (let. 1320) will induce some of your able con- [1432] I HAVE gained a practical knowledge of this tributors to favour us with their views on the subject ram through having fixed several, and knowing a of the identity of the rays of heat and light. Many of little of the theory-all theory and no practice is apt us, I have no doubt, have met with the same difficulty to lead any one astray, even one as learned as H. W. as "S. P." in understanding why one ray should, as Reveley (let. 731), for some of his statements about the Jamin says, possess two properties, either of which ram are not only anything but correct, but are simply we can, in spite of what he alleges, destroy at will. I ridiculous to any one who has had practical experience cannot see how Jamin can hold that a determinate with that astonishing but simple apparatus.-I will part of the mixed spectrum contains two inseparable answer "Hydraulic (let. 641) to the best of my rays, one of light, the other of heat, and yet in one judgment, without stating the reason for this or that, and the same direction of refraction, but one single as I think it would take up too much of your valuable vibrating movement, having two properties and two space. effects. Is it a fact that we cannot obtain rays of light | Q-One or two rams? 4.-Two. Q.-What size? 4.-Three impulse valves. Q.-Form of air-temal! 4.-The shape of a pear. Q-Form of valve 4Ball valve. Q.-Size of drive-pipe? 4.-2in. Q.-Ang of ditto? 4.-Have your supply-cistern aft. dep and let your drive-pipe come in the side as near th bottom as possible, and let it be 90ft. long, and fry t as straight as possible from supply-cistern to ram Q.-How the joints should be made? 4.-The pipe should be stout cast-iron, and the joints cauled with Q.-Size of main? 4.-lin. Q-Where it lead. should be taken off air-vessel? 4.-The bo 4.- From 14 Q.-Water raised in 24 hours? to 2,000. HYDRAULIC NO. A WARMING APARTMENTS. [1433] I HAVE lately noticed in your salm various queries and remarks about the use of gas ! warming and cooking. My knowledge of chemistr and gases is not deep, but my experience in gas ware ing may be interesting to your readers. I have a rong shop, or anything else, it is, in fact, my santr about 15ft. by 12ft., which serves for laboratory, wei When I use this room in winter the first requst to warm it easily and rapidly; with an ordinary fire in the grate it required three or four hours bel the room got warm; an iron stove with a pipe lea into the chimney was a little better; gas is use other parts of the house, so I had it extended to sanctum for warming and lighting. The first thing was to stop up the chimney out in warm weather. The gas was brought down! some slates in such a way that they can easily be take the hearth by an india-rubber tube, at the end of was a Bunsen or air burner of large size; by py management of the quantities of air and gas I get a large flaring blue flame nearly a foot long. This flame alone gave out a considerable amount a heat, and warmed the air, which rose to the top It was, borse, room, but left the bottom cold. very wasteful way of warming, besides being ad cient, and the next thing wanted was to place sa thing solid to get hot and radiate the heat all rud I fixed to the mantelpiece one of those brass they use in the kitchen to hang the meat fros-2 name I do not know, but it is a sort of mis crane-from this I could, by means of a piece of cost and hook, hang anything in or over the dame I knew that iron would be objectionable, bai bine at hand a door of an old stove, by way of trial it in the flame, which I turned up to its full strengt the iron soon got red-hot, so I diminished the tan but when the iron was hot enough to radiate E. got the well-known smell of hot-iron, or burat a, whatever it may be. This showed that the material to radiate mast be metallic, so I tried one of the porous pots used electro work; it got hot rapidly, but the heat braku to pieces before I had time to form an opinion of a I then tried an old black-lead crucible, which ca got hot and radiated heat fairly; but I began to gs › horrid smell, something like garlic, which I knew pr ceeded from sulphuretted hydrogen or bisulp carbon, or perhaps both of them, and as these are unhealthy, the crucible was a failure; before grat up, I tried it in all sorts of ways, but co avoid the smell, which often gave me a severe he The next thing I tried was a lot of pieces of stone kept together by some wire twisted round they heated and radiated better than the sim crucible, but gave ont more smell than ever. It tried a large lump of pumice-stone in one piece; th like the smaller pieces, radiated well, but the se garlic was as bad as before. Having thus far failed, I was in a puzzle. I get heat and radiation, and all appeared to se except these gases, which showed their presence smell and by the headaches they produced. Ora ally I managed to get heat with very little smell, tried to find out the reason, but did not succeed. About this time I saw one of the gas-fires wit bestos and clay; it was in an ordinary fireplace. the gas underneath, and as the chimney was left t the greater part of the heat went up the cher this gave me the idea of asbestos, and for sixpence got a handful of it in a tangled mass, tristed a loosely round, and hung it in the flame; it get redat once, and radiated well, but there came tat smell as before. The asbestos was too tightly pre together, for the outside got red-hot, while the of it remained the same colour as before; I the opened out the wirework and spread the aber thinner; this was an improvement, but it led us important discovery about the garlic smell. over the flame, and one day I accidentally palled a I had a hooked wire to pull the asbestos about in the asbestos through which the flame pass F ignited another blue flame above the abestos; at of this the truth flashed upon me at once; this p of the gas had been escaping unburnt, thas caus smell and the headaches. The articles I had used, sta as abestos, pumice-stone, crucible, &c., really ade gauze wire, allowing the passage of gas but not of through them. This discovery made the matter more simpla, after a few trials I rigged the fire thus:-I got s trap-one of the sort that consists of a domed wire on a base board-took off the base board and it aside. The wire dome is inverted and hang b loop in the flame; the asbestos is placed inside dome and pulled out between the wires so that th hang down, making the whole concern look like a somewhere near the centre an opening about sa wide is kept clear of abestos, so that the fame a through and ignite the gas above. This I have I by a little blue flame above the abestos, showing that gas is burnt and does not escape. I have never found it necessary to attend to getting rid of the products of combustion; the sulphuric acid and water liberated do certainly rast steel rulers hanging against the wall, but this comes on slowly. As to the gauze-wire burners, I do not use them, but purchasers should remember that the gauze will be burnt out in perhaps two or three months, and there should be some means of renewal. The gauze is generally kept in place by a ring tightly fastened by two or three screws, and by the time it is burnt away, the screws are burnt in their places so fast that they cannot easily be moved, and the whole must be sent to a maker; thus the renewal of the gauze becomes expensive instead of being a simple matter that an amateur should be able to manage. Whether a ganzewire burner or an air burner be used, it is important to attend to the proportions of gas and air; altering the quantities of them often makes the difference between success and failure. If properly proportioned, the flame will be blue, tinged with red at top, and should not give out any white light. I have lately seen a new style of stove for warming, which appears to me superior to any. I have not seen sufficient of it to give an accurate description, but the air is admitted by a pipe from the outside of the building, and passes into a sort of oven heated by gas before getting into the apartment; it is a patent article, and can be seen in operation in the shop of Messrs. Hockin & Wilson, 88, Dukestreet, Manchester-square. As to the asbestos, I find that the looser it is the better, and to make it into a tassel shape the fibres should be pretty long. I some time ago bought some asbestos in a solid slab about 9in. long; this slab is formed of straight silky fibres of asbestos, but I do not know how to separate them; by putting the mass in a dish of water I can separate the fibres, but when I take them out of the water they all stick together again as they dry. I tried burning them, but it seemed to make them stick together harder than ever. If any of your readers can tell me how to separate the fibres, I shall feel obliged. CYCLOPTYCHIUS. SOCRATES. [1484] CYCLOPTYCHIUS is a genus of coal-measure fishes based upon specimens that were submitted to Professor Huxley during the meeting of the British Association in Aberdeen, and named by the learned Professor on that occasion. I think I am correct in stating that there is not any published record of the genus to which reference can be made, and I believe the Professor is not in possession of MS. or other record concerning it. Fishes of the genus Cycloptychius have been found in the Staffordshire collieries, but until the discovery of the specimen now before me the existence of Cycloptychius in the Northumberland coal-measures was unknown. I am again indebted to Mr. Sim for the privilege of examining the remains of this rare and little-understood fish, and shall endeavour to convey to your readers some information respecting it, so far as may be inferred from the specimen in my possession. course. The specimen rests upon a piece of shale, which is 7in. long, and 24in. broad, and covers the shale over its entire length to about two-thirds of its width, and consists of scales, opercular, jugular, and other head bones, jaws and teeth. A jaw which is distinctly visible appears to be a mandible. It is upwards of 2in. in length, and on a portion of its alveolar border it exhibits teeth of three sizes, similar to those that are in the jaws of Pygopterus, Gyrolepis, and Acrolepis, but rather smaller in proportion to the size of the fish. The mandible tapers gradually to the an. terior extremity, and at the extremity there are two of the larger sized teeth in close proximity. All the teeth, large and small, are tipped with enamel, and are arranged alternately, as in the other genera named. The jaw is marked with interrupted longitudinal ridges that present a slightly waved appearance in their Scattered over the specimen there are opercular, palatoquadrate, and jugular plates, which much resemble those of Coelacanthus in their surface mark ings, in the extreme polish of their inner aspects, and in their size. On the outer aspect they are covered with delicate inosculating ridges. The scales, which are tolerably numerous, have a tendency to the cycloidal form, and the ridges, which are very fine, cover them somewhat cycloidally. On first examining the scales and head-bones, I thought they might probably belong to a species of Colacanthus, but the teeth render that theory untenable, as to the teeth of Coelacanthus are small and villiform, while those of our specimen are of three sizes, some of them being large, and all being tipped with enamel. The scales differ in form from those of Pygopterus, and the ridges, unlike those of Fygopterus, cover the whole surface. The ridges of Acrolepis are greatly more coarse; and those of Gyrolepis run along the longer diameter of the rhomboidal scale. I am unable to say how far this description agrees with the verbal description of the fish given by Professor Huxley, as my only knowledge of the genus is based upon specimens received from or in the cabinet of Mr. Ward, of Longton, and others on the shelves of the British Museum. Newcastle-on-Tyne. T. P. BARKAS, F.G.S. BICYCLE WHEELS. [1435] IN reply to "J. H." (let. 1828, p. 471), respecting phantom and spider wheels, I have had both in se during the past twelvemonth, and without doubt have given them a fair trial. My experience in the phantom wheels with the rubber tires was this. They kept in tolerable good order about three months, when I discovered the rubber tire to have a curious swelled appearance, resembling a number of blisters at the places where the nails were put in to hold it on the felloe. On examination I found that a quantity of small stones had worked in through the nail holes, and cut their way through the rubber; I was continually taking these out, but still they got in again, and as they made the machine jar unpleasantly I put on a new tire, without nails, which was a great improvement, though it was subject to come off in turning corners quickly. The plan I used is sketched on p. 476, No. 306, only I did not use pincers to press in the plates. The phantom wheel has a wood felloe, and as it gets a few months old goes into all sorts of shapes and makes the riding anything but comfortable, so I replaced mine with a pair of spiders. They have much the same appearance as the phantom, without its failings. The felloe of the spider is iron, and of course keeps its shape much better, there is more rubber, and of a better quality, with no hole in the surface to admit stones; consequently, it was better, but the price is high, out of the reach of the many, I am afraid. From experience I have no hesitation in saying that the spider is the better of the two, but before "J. H." has anything to do with either I should advise him to wait a few weeks, and I believe that he will hear of a wheel lately patented that is far superior to phantom or spider. I lately got a hint from a bicycle-riding friend, who has bought a pair of wheels, the first made I believe, and have not only seen them, but have ridden many miles on the roughest of roads to try them, so can give a fair opinion of their merits for the benefit of every bicycle rider. I need scarcely say that in the wheels of a bicycle lies the chief consideration; any failing in those alone will spoil the best-fitted ironwork: hence the importance of getting the best quality. The following are a few particulars of the new wheel, as well as my poor ability can give them. The wheel is made of metal, the felloe is steel, of a bell-shaped section, fitted with rubber more than an inch thick every way; the spokes have a neat plan of tightening up at any point, by a simple arrangement without the use of tools; there is also a new treadle, upon which any part of the foot can be placed with ease, giving the ankle into play, and avoiding lifting the knees so great power to the rider over the machine, bringing high as in other treadles, and is not so tiring for very long journeys, as the position of the foot can be changed. but I think that it will soon be before the readers of I should send a sketch of the wheels and treadles, the MECHANIC in the shape of an advertisement, and as I have not asked the permission of the inventor I am afraid I have gone too far already. J. M. KITCHEN BOILER EXPLOSIONS. [1436] I CORDIALLY agree with Mr. Debnam (let. 1326,p. 471) in his contempt of the views of "Forty Years' Practical Experience" as published in his letter to the Times, but I flatly contradict his assertion that "there seems to be no direct plan to prevent the explosions of hot-water boilers in frosty weather." Since the explosion of a boiler in my neighbourhood a short time since, my attention has been continually directed to this subject. I was told precisely the same tale as is told by F. H. Godstone (let. 1325, p. 471), "that fusible plugs are a delusion and a snare, and the safety valves a source of dangerous security; "that the so-called "upcast pipe" was as liable to get frozen as any other pipe, and that I might as well try to fly as to invent a plan to prevent explosions in frosty weather. However, I did not fold my arms and quietly resign the poor domestics to their fate, but am prepared to combat the difficulty in more than one way. My first"plan" (but none of my plans are original. I merely wish to prove the practicability of those plans already proposed), is the double boiler system. Inside an ordinary open kitchen boiler place the close boiler, or that supplying the hot water for baths, &c., and every difficulty is solved at once. The close boiler being entirely surrounded with water can neither get red-hot through shortness of water, nor generate high pressure steam when the pipes are closed by frost. The former of these statements is very obvious, the latter may require some explanation. The degree of heat required to evaporate steam increases with the pressure to which the water is subjected, as will be see by the subjoined table :Table showing the relation between the pressure and temperature of steam. Pressure in lb. per square inch. 14.7 (the atmosphere) 20 25 30 35 40 50 100 150 200 Now, as no more than 212° can be supplied by the water in the open boiler to that in the close one, it is very evident that steam cannot be generated. But it may reasonably be 'objected that this plan is expensive and could only be carried out in fixing new apparatus. What seems generally required is a simple and inexpensive addition to the ordinary kitchen boiler that will ensure perfect safety. Fusible plugs are suggested, but F. H. Godstone tells us " they are a delusion and a snare." "Forty Years' Experience seems terribly afraid of "flooding his kitchen," while "Constant Reader" (let. 1213, p. 319) says no kind of metal will melt while it is in contact with the water. Now all this is bosh. Let the reader wishing to ensure safety in his kitchen refer again to the table printed above. Let him fix the pressure he choses to subject his boiler to, and "beg, borrow, or buy " a fusible plug to melt at the temperature indicated in the second column of the table, and place it, not in contact with the fire, nor at the bottom of the boiler, but on the top, in the most likely place to be in contact with the steam, should any be present. He will find that when the pressure fixed on as the limit of safety is reached the plug will melt and the kitchen will be flooded with steam, and perhaps with a little water, an inconvenience certainly, but if he wishes to avoid it let him procure a common wrought iron "flange," bolt it on the top of the boiler and rivet in the plug in the centre of this flange; then screw on an "elbow " or L piece a length or two of pipe, which will carry the objectionable steam and water out of harm's way, to the sink. Then again, the question arises, can we make plugs to melt at any required temperature? Most certainly we can. Since coming to this conclusion, I found the following table in Holtzapffel's work:Alloys and their Melting Heats. No. 1, 1 tin, 25 lead, I have read somewhere (how far it may be true I can. not say) that fusible plugs, after being subject to the long-continued action of heat, will stand a much higher degree of heat than can be theoretically expected of them. Should this be the case, I would advise those using them to put a new plug in at the commencement of every winter. There seems to be a good deal of misunderstanding amongst some of your correspondents writing on fusible plugs. Thomas Holt (let., 1327, p. 471) proposes, in order "to prevent explosions caused by shortness of water," to "have a common lead plug inserted in any part of the boiler exposed to the immediate action of the fire; this, when the boiler is empty, would melt and leave a hole for the escape of steam formed by the passage of water into the hot boiler." But there is a possibility, nay, an awful probability, that sufficient water may be kept in the boiler to cover the plug. Viewed in this light, fusible plugs are indeed "a delusion and a snare." To The two plans given above seem at first sight all that is needed to ensure perfect security in the kitchen and " parts adjacent." But I will undertake to prove that in addition to these we must have a safety valve. take an ordinary case, we will suppose the boiler and pipes to be left, as they always are, quite full. In the night some of the water in the pipe freezes. The boiler is then hermetically sealed; a fire is lighted in the morning, the water expands with irresistible force, the boiler bursts (not explodes), and that despite the double-boiler plan or fusible plug. It is evident, then, that a safety valve is indispensably necessary even when either or both the other remedies are used. Every experienced person on hearing of an explosion says "there ought to be a safety valve;" every man of "forty years' experience" seems to answer" You know nothing about it." I have never heard a satisfactory Such reason why safety valves are inadmissible. I think I have now disposed of all the objections raised by this latter gentleman against safety valves and fusible plugs. I should like to send a sketch of my valve, but I have already far exceeded the intended limits of my letter. However, at some future time I may send a sketch of it, as well as of another, in which the water is prevented from touching the valve till an unsafe pressure is reached, thereby obviating the inconvenience caused by the incrustations and consequent "sticking fast" and leakage of the valve. THOS. WATSON. THE SEASONS OF THE GREAT YEAR. [5861.]-COMPENSATION BALANCE. (U. Q.)-Since this query seems likely to pass unanswered, I bare "S. P. W." will pardon my replying for him. I would ad Vise "Economy" to be satisued with a steel balance in his three-quarter-plate watch, and not change it for a watch go worse, it would certainly not make it keep want to be adjusted: for if the latter did not make the any better time.-NOBODY. [1437] "G. T. F." (let. 1265) puts a question to existence; for, even when we call it "infinitesimally compensation, which he expressly states he does not Mr. Proctor, regarding a lecture recently delivered in Dublin, wherein some very startling statements were made in respect to intertropical temperatures, and Mr. Proctor answers, at p. 466, as he was sure to do, to the purpose. Still, as "G. T. F.," and probably others of your readers, may wish for something more definite, I trust Mr. Proctor will pardon me if I venture to supplement his reply to a question not addressed to myself. I wish to show how unfounded are any fears that might be entertained with regard to any immediately anticipated rise of temperature in the equatorial region, of such a nature as to interrupt communication with our Australian colonies. It has been my lot to traverse the distance from one tropic to the other twenty-six times, during which I made carefal notes daily of the highest and lowest temperatures, taken with a good registering thermometer, compared, several times a day with other thermometers; and send you, below, an excerpt from those notes. The table would have possessed more interest had I added the latitude to each observation. I abstained from doing so, however, from a knowledge that it would add to the expense of setting up, and it will be understood from the dates whether the latitude was north or south, and I may add that this was on board a large wooden steam ship (paddle-wheel), going about 10 knots an hour, but the last voyage in an iron screw; all in a cabin on the main deck. It will be perceived that the temperature is in no case the highest at the equator, nor, indeed, as might be pre-supposed, at that point of the ecliptic where the sun is situated, i.e., where a man's shadow surrounds his feet, though this in some measure obtains. What we might the most reasonably expect would be that the greatest heat would prevail at the spot that the sun has recently quitted, for there would be the greatest radiation; but here, again, our expectations are not absolutely fulfilled, for we not infrequently find the temperature higher at a degree or two on either side of the equator than on the equator itself, and often at both sides. The scale is, of course, that of Fahrenheit. Finally, it will be said that the heat, after all at sea, in tropical regions, is nothing so terrific, seeing the thermometer registers no more than we experience in England in summertime; but it must be remembered that these temperatures prevail there all the year round, and that, if in England we reach to 80° in the day, there is a fall of 20° or 30° in the night; so that there is time to recover; but there the fall is but 2 or 3 in the night, and you are kept in a constant state of simmer; and with a few years of this you get so red hot through that it takes some other years to cool. F.R.C.S. MATHEMATICS OF LIMITS. [1438] As Mr. Proctor looks on this question as one of "mathematical intuition," and as almost inexplicable to other mental organizations, I wish to point out the "metaphysical difficulty" which affects it. We speak of the infinite as if we possessed a clear and positive idea of the meaning of the term, although our imagination in this respect is totally erroneous. We have a clear idea of "increase of the finite," and also that there is "no end to this process." But this, unquestionably, is merely a negative idea, and that it cannot give a perfect conception of (say) infinite space may be proved mathematically, inasmuch as finite space is not "a measure" of infinite space. Thus let us assume any finite space (however great), and say that Ex infinity is = "infinite space," we come to the absurd conclusion that 2 x infinity is equal double infinite space! This reasoning, however, does not affect the soundness in the mathematician's views, for, although he can never arrive at the "goal of ininity" in his approximations, he can easily go so far as to prove that the difference of his "ultimatum" must become so small as to be utterly insignificant, and therefore may be looked on as ceasing to exist, even although this actual non-existence could only be produced by an approximation which has no end. Thus, for instance, "Sæpe" is correct, geometri. cally and metaphysically, in saying that there must be a triangle so long as the angle in question has any real vertical angle of "his triangle" is also infinitesimally small," the only legitimate consequence is that the small, and at a distance indefinitely great. But let two lines (which included this small angle) and he will, Sæpe " carry on mentally the approximation of the I trust, perceive that their coinciding in direction (and them) is the mathematician's legitimate ultimatum. the non-existence consequently of any angle between should wish to point out some erroneous'views geneIf you can allow me room in a future number, I rally accepted by mathematicians which have arisen from the false notion that "we can obtain or do possess a clear and positive idea of the infinitely great." HENRY HUDSON, M.D. [5948.]-PEPPER'S GHOST(U.Q.).-I have constracted "W. B.'s." I can effectively illuminate the figures a model of Pepper's ghost, about the same size as coal gas or paraffine lamp. The under stage of my mold is lighted by an argand gas-burner, with a tin releeter behind and a common bull's-eye condenser (from & watchman's lantern) before. The light is placed at ab 13in. from the stage. The upper stage is lighted means of a strip of copper pipe pierced with six very justing screws to enable the exhibitor to lower the lights small holes. The gas cocks are fitted with stops att quickly without extinguishing them entirely.CHEVALIER. [5950.]-DOUBLE BLAST BELLOWS (C. Q.)-Theat vantages are that they stand in half the room that her bellows do, and they are easier to work than single EXTRACTS FROM CORRESPONDENCE. bellows, as every stroke of the lever produces à dont quantity of blast; in fact, they produce a soft, regna: and soaking blast, and a 26in. pair of bound desig bellows would give quite sufficient blast to weld an having worked with them both.-ROSETTA. shaft, or larger if required. I speak from experiense, MUSIC.-"H. E. A." says:-"I quite agree with your correspondent, Fleur-de-Lis,' in his remarks on music, but instead of a few articles would it not be better to have a good treatise at once, as I think it is as important to know how to use, as it is to make our organs, &c.? I trust the subject will receive the at tention of some of our readers." PATENT GREASE CUP.-"C. K." writes usThat the tallow cup patented, by Messrs. Page & East, and described in let. 1819, p. 469, is nothing new, as he has turned out many of them during the last 14 years. He advises those gentlemen to take a tour through North Wales, where they will find plenty of them in the colliery dis ricts, and they are made by three firms to his personal knowledge. CLOUD VESICLES.-All that can be said with reference to the balls seen by Otterham (let. 1314, p. 468) is that they do not appear from his account to be hollow, being rather dusky in the centre. His measure, 3-16in., may be called one-fifth. The objects may have been insects seen through the mist, and therefore distorted.-M. PARIS. SPEED ON RAILWAYS.-"Suffolk Amateur" says: "I think it could be clearly shown by statistics of railway accidents that the running off the rails is chiefly an accident to which the narrow gauge is liable. ideas were of the grand order (witness the Great Eastern Brunel, the originator of the broad gauge-all whose steam ship)-might have been over-grand, in the 7ft. width. But there can be little doubt that in respect of power to accommodate a large traffic, safety, and speed, the broad gauge is far beyond the narrow. Expense and profit to shareholders is another question, and these have probably ruled the matter and decided the battle of the gauges." CHEMICAL NOMENCLATURE (Lets. 1276, 1331, P. 471).-With great deference to "Urban," I cannot see what my knowledge of the composition of the audience, or of the subject, has to do with the mixture of However, I four systems of chemical nomenclature. happen to have paid some attention to the subject, and from much experience at lectures I can form an opinion as to the audience that required to be shown the properties of carbonic acid gas, and the use of a test paper for acids and alkalies.-M. PARIS. [5740.]-COMPENSATION BALANCE.-The use of the heavy headed nails screwed into the rim of the balance wheel is not only to weight the balance, but at the same time, to have the weights separable from it, so spare holes drilled round its periphery. The rim of the that they can be taken out and screwed into other and balance being cut through in two places diametrically opposite, is thus formed into two arms, each passing half way round, and each attached at one extremity to a spoke of the balance. As these arms bend more at their severed extremiti s (inwards and outwards), under the influence of heat and cold, then at the extremities attached, and as these weights can be shifted about on are carried inwards and outwards to the right distance these arms, they can be placed in a position where they by the expansion and contraction of the metals, and thus produce an adequate effect in compensating for the temperatures.-NOBODY, Mills "R. R. S." mentions are set in a metal frame, and [5837.]-TO MILLERS (U. Q.).-The American Grist work horizontally. The runner is of conical form, working in the bedstone which is built round it in the metal [5985.]-VIRGINIA (U. Q.). [6377.)-SAN FRAN CISCO. It would take several coluinns of the ENGLI MECHANIC to answer "Saepe" and "Agriculturist full. The state of society in San Francisco is tr Yankee, only a little more so, That is to say, it is a tensely vigorous, impetuous. rushing. The "aly dollar" is sought after with all the powers of soul, and body. Gain, comparatively speaking, is thing.. Business is the idea and life of the place. its business is more of a lottery than anywhere a the States. Whilst one man becomes rich another lay everything. Its morals and modes are Parisian; py and loose. Nevertheless, many of its inhabitant are men of sterling worth and of refined manners. Lis popular; yet the man who minds his own busines rather cheap there. The knife and the pistol are o safe there as anywhere in America. It is a godas for a first-class mechanic; it is a very poor place lors indifferent, indolent, or sottish man. It differs from al other American towns in having a large nacker d Chinese residents. They act as house serva), messengers, small tradesmen and mechanics. Ther good-natured, docile, obedient, and generally bones. I will endeavour to answer "Agricul.urist" in the of his queries. (1) No. (2) No (as henceforth explore (3) Western Virginia, Southern Iowa. (4) Hot in cold in winter; they only differ from each other in ing; yes, if you mean general knowledge of farming duration of these extremes of periodical temperca (5) No, if you mean the precise method of English This last question has its difficulties. The word " man's son it not, a young man of culture, refinement, acest brings doubts to my mind. It means to work rather with the mind than with body, is upon, has his boots cleaned, and not apt to mingi e freely, or on almost an equality, with servants: The are no gentleman's bailiff's or farm superintendens the States. Ninety-nine out of every hundred farmer work, work with their own hands. They employ termediate overseer. Every man on a farm works R is the great requisite. There is plenty of brain. M is in great demand. Plenty of farmers would de a situation, paying you well, if you would bend and lovingly to manual labour. Plenty, also, wol glad to take you in, merely to look about, if you wal pay for your boarding, otherwise not. Farming is ev part of the United States is a hard work, yet it is re munerative and independent. I would not advise to go either to Virginia or to Iowa. Virginia is going reconstruction (having been a Slave State. T ginia is looked upon as more or less dead. I would prett saying that it is, just now, in ruins. Iowa is a fer state, but flat, very cold in winter, and too far from the chief markets. Go to Ohio, Southern Indices Michigan. Michigan is a fine farming state, esp Southern Michigan. It is undulating, romantic, frie Its great staples are wheat, wool, and fruit. The drawback is its rather long winter. But it is bey and bracing. If you intend trying the States as a farmer, or Michigan. If you have money, take lodgings either in a village or with a farmer, and so for six months. Go about; visit the people; see I have lived in America over twenty years, conso always for sale. A good farm always enhances in they do things. They will gladly enlighten you. F speak from experience. I have preferred giving go to Ohio facts rather than fiction.-CAMBRO. [5990.]-ENHARMONIC PITCH-PIPE (U. Q)—b this the pitch-pipe which gives any required noge of s 4s. 6d. at music shops.-M. P. termediate sound by turning one end down: F [5993.]-HALF SECONDS PENDULUM-Inc tinuation of reply to Mr. Tompion I beg to forward lin. long vibrates 375 times a minute, therefore di rule I found given in a published lecture. A pend 875 by the number of oscillations required, the q multiplied into itself will be the length in inches quired.-HOROS. in Piccadilly what was done with the hair so plent [6000.]-HUMAN HAIR (U. Q.).—I asked a hairdr spread on the floor? and he replied, "It is thr away."-M. P. pump that ever I saw or heard of is a plain cylinder a [6008.]—BRAMAH PUMP (U. Q.).—The only Bromsh solid plunger for the Bramah hydraulic, to which are fitted two non-return valves, conical, one in suction the other in the injector.-JACK OF TRADES. [6008.)-BRAMAH PUMP (U. Q.).—This is the onnary hydraulic pump, called sometimes Bramah puno, fter the inventor Bramah, and may be seen on almost very steam-engine, and called there the " feed pump." 'he size you mention, 3in., is a very large pump, and ould require great power to work. The sizes run from bout gin. plunger up to and seldom exceeding 2ļin. on resses, but on soda-water machines they are somemes larger, being required to put on 50lb. or 60lb. on he square inch.-GODSTONE LABORATORY. seen in India years ago. Ever since this invaluable [6174.]-CURIOUS EGG.-If lead is melted and [6009.3-GINGER ALE AND CHAMPAGNE CIDER -I can only answer for tin plate known as crystallized. pply in a heated state dilute nitro-muriatic acid for a w seconds, wash off with water and dry, then lacquer; rheat the plate slightly, and hold over tub of water; ab its surface with sponge dipped in liquor made of quafortis two parts, distilled water one part; when osted enough dip in clean water and wash extremely ghtly with piece of cotton or feather, dry and lacquer. -GODSTONE LABORATORY. (6014]-MACKINTOSH (U. Q.).-A modest request! Yould take a couple of pages to answer satisfacorily.-GODSTONE LABORATORY. (6018.)-CHLORAL HYDRATE (U. Q.). -Decidedly ati-spasmodic. When you recover you feel as though ou had had a refreshing sleep, no unpleasant sequelæ imilar to the effects of chloroform. Dose 10 to 30grs. -GODSTONE LABORATORY. [6021.]-SOLUTION OF LEATHER (U. Q.).—Solution fleather is neither more nor less than common glue, nt leather may be boiled until it is half converted into lue and sticky. then allowed to dry and varnished, but no longer flexible. I have coated several pocket asks (bottles) in this way. It shrinks greatly.-GODTONE LABORATORY. [6021.]-SOLUTION OF LEATHER (U. Q.).—I know f no solution of leather. You can get a solution of ides at any oil or colour shop, generaly known by the lame of glue.-JACK OF ALL TRADES. [6026.]—GILDING ON SLATE (U. Q.).-Use equal arts of glaire and water; when dry, rub with whiting, nd be sure that it is so; put your figures on with gold ize and a little chrome or vermilion just for a tint, to ee where you are going. When dry enough, apply the fold leaf; all colours should be put upon slate dead, ind varnished afterwards or polished.-JACK OF ALL TRADES. [6026.]-GILDING ON SLATE (U. Q.).—Question hardly explicit enough. One way to do it is by using a amel-hair pencil and gold size to trace the pattern or design, and allowed to dry until it becomes "tacky" o the touch, when the gold leaf is gently pressed on nd then carefully and lightly rubbed over with a piece of wool or wash-leather to remove superfluous gold.JODSTONE LABORATORY. [6025.]-DYEING SHEEPSKINS (U.Q.).—The wool wants feeeing from grease, and well washing with limewash and water; afterwards apply Judson's simple dyes (I believe they can be got at any of the chemists); they likewise do for grasses and feathers.-JACK OF ALL TRADES. [6033]-WATER ENGINE (U. Q.)-If single acting 492 gallons per minute, if double acting, of course, double that quantity. Pressure has nothing to do with quantity as the cylinders can only be filled and emptied given number of times per minute.-GODSTONE LA [6175.1-SEPARATING ALCOHOL.-If a mixture of alcohol and water is placed enclosed in a bladder in a warm place the water will evaporate, passing through the bladder, aud the alcohol remain.-SUFFOLK AMA TECR. [6211.]-DORMICE [6215.)-RIPPLES AND WAVES.-I am much obliged [6233.]-THE EFFECT OF METAL ON ICE.-The AMATEUR. as we please. Thus:-Concentric with the circular pro- [6245.]-EQUATIONS.-In his solution, "Mr. T. B." y4-14 y2 + 49 11 y whence y = 2. May I ask him how he solves this equation?-X. Y. [6246.]-GEOLOGY.-"OLD BRIGHTON."-Can Mr. Underhill refer us to an account of this village and its was quite submergence? I always thought "Brighton a new name, contracted from "Brighthelmstone" by George IV.; and Brighthelmstone must have been a remarkable hill-top village, the church and workhouse (inscribed with its name) now marking nearly the highest ground in the present overgrown city. Moreover, the spot of coast where it changes from tertiary flats to chalk cliffs, is of all points the least liable to encroachment (apart from earthquake) either of the sea on land or the reverse. And Sussex, or the whole east part of the channel, is one of the districts the furthest in the world from not only volcanic, but even erruptive rocks of any kind; and also from earthquake sites, and from great dislocations. Not that any of these four things have much apparent connection locally-there is no volcano within many geographic degrees of earthquake-riddled Caraccas, Jamaica, Lisbon, or even, in the case of Jamaica, any eruptive rock. Again, neither the most actively volcanic districts, nor shaken one like the above, show anywhere, I believe, so many erupted rocks and huge dislocating faults as the N.W. of England, hundreds of miles distant from any trace of crater, and The only very any serious historic earthquake. apparent connection is that near all active volcanoes there are frequent but slight shocks; and this is also the case where the severest earthquakes occur, namely, along certain linear mountain chains, which are among the longest traceable, but not the highest, nor most broken, nor most associated with vents, nor even with most primary rock.-E. L. G. [6249, 6467, 6468.]-FOUR POINTS.-It will be found on trial, that my solution of the problem of describing a square whose sides shall pass through four given points in a straight line is perfectly general and answers "E. L. G.'s" 2nd and 3rd cases, regard being had to the order of the letters. Call 1, 2, 3, 4, the sides of the square, and let A, B, C, D, be the points through which will lie in the following orders. they respectively pass, produced or not. The letters For Prob. 1, A B C D. (6249), For Prob. 2, A C B D. (6467), For Prob. 3, A C D B, (6468), and the solution is the same in all; viz., draw BE perpendicular to A B; join AE and produce it. Through B draw a line parallel to A E, and through C and D draw lines perpendicular to it. These will form the required square, whose sides will each of them be equal to CD cos. E A D.-O. F. [6258.]-HYDROGEN LAMP.-It is to be feared structions he has had offered to him during his studies, if he does not know how to construct a hydrogen lamp, or what spongy platinum is. The best thing he can do shop.-F.R.C.S. is to purchase one for a few shillings at a German toy [6292.]-VARNISH.-White shellac, when new, will dissolve in the usual solvents, but on exposure to the air it is gradually changed and presents the characters described by your correspondents. I have been informed that if it is kept under water it does not spoil.-J. G. [6027.]-DOOR MATS, TO MAKE (U. Q.).-Door [6238.]-WATCH JEWEL.-I do not think the chrysonats can be made out of sugar bags by passing what the lite, called also olivine and peridote; which, according to sailors call thrums through them with a pricker, marlin Prof. Ansted, is an olive green mineral, is much, if ever, spike, or a butcher's steel will do as well; the foundation used for the above purpose, indeed, I do not recollect s taken and folded, and the pricker passed through; the having ever met with a jewel tinted with any shade of hrums are all eut off to about Sin. long: they consist of green. The chrysolite of commerce is a pale green stone. he odds and ends of bagging, jute, rope, old cables occasionally used as a gem, and, I believe, of about the beat out, grass, cocoa-nut fibre, &c., and the cleanest same consistency as the garnet. The garnet, though it aken care of, to be dyed for the border, which is gene-enjoys a questionable reputation amongst horologists, is rally red and blue, and coloured with logwood and Prus- often met with as a watch jewel, and almost as fre3iau blue. A back is put on them afterwards, the rope quently it is found wanting in hardness. The minerals mats are sometimes made from the rope twisted and the most prized are those classed under the head of sometimes plaited and wound about and tied with yarns "salts of alumina, corundum; the minerals collected to-F.R.C.S., No. 8," has scarcely attended to the inand a packing needle in various forms according to a gether under this name, and consisting essentially of person's fancy.-JACK OF ALL TRADES. pure crystalline alumina coloured by iron, and other metallic oxides, differ enormously in colour, appearance, line and the other granular. All specimens agree in posand value. There are two principal groups, one crystalsessing extreme hardness, inferior only to the diamond, and this gives great value to the granular varieties, which would otherwise be worthless. 1. Crystalline varieties. These are generally transparent, and coloured blue or red. The fine azure or indigo-blue varieties are called sapphire; the red, oriental ruby; the yellow, oriental topaz; the green, oriental emerald; and the violet, oriental amethyst. Of these, the ruby is the most valuable, and fine stones often exceed the diamond in value. The largest known ruby is in the crown of Russia. Corundum is the name given, generally, to rough, opaque, dull masses. 2. Granular varieties. These are better known by the name of emery. The best kinds are those having & blue tint; but many substances are sold under the name of emery which contain no corundum." I am of opinion that the material the most used, at least from jargon; colour, brownish red, and red of clear tints; also its description, is the zircon, called also hyacinth and It is a silicate of zirconia, coloured generally with iron. yellow and grey; streak, uncoloured; lustre, adamantine. Its hardness (near corundum) renders it valuable for jewelling watches." The smallness of the pieces required for jewelling enables the corundums that would otherwise be fit only for grinding into polishing powder, to be used, as also those large enough, but not of sufthat there is abundance in the supply which renders it ficient beauty to be set as gems, besides the zircons, so almost needless to use chrysolite, when there are better stones to be had at the same price; yet sometimes, though the instances are rare, jewelled holes are worn so oval as to suggest that they were mere crystal or glass.-NOBODY. BORATORY. [6046.] HARDENING CHISELS (U. Q.)." Mill bills," I suppose you mean. The ordinary way is to heat them all over bright cherry red, dip about an inch of one -end into water and move about until hard, then the other end; now look sharp with piece of gritty stone or brick and rub hardened parts bright in one or two places, so that you may see the colour come down to straw colour or spotted purple, according to the quality and hardness of steel; if one end runs down before the other give it a dip to check it; but the secret lies in using water that has been used for a long time, years often, and not quite cold, and judging correctly the natural temper and hardness of the steel; of course, when both ends are the right temper, plunge the bill into water to cool.-GODSTONE LABORATORY. Will "Godstone Laboratory" oblige by sending the editor his address?-ED.] [6050]-QUINSEY (U. Q.).—If "Subscriber from the very First Number" is of the masculine gender, and does not wear a beard, if he can allow that appendage to grow he will find the greatest benefit from it. Tried. -EDWIN HOLMES. [6080.]-STONE FOUND IN COAL (U. Q.).-Probably not a stone, but a fossil of some sort. Perhaps Mr. Barkas could tell if it was sent to him. Almost impossible to say without examining it.-S. R. [6109.]-FLAVOUR OF NASTURTIUMS (U. Q.).-I do not think any one has extracted the flavouring principle of the nasturtium, a pungent juice possessed by all the Cruciferæ. I do not think the seeds pickled are pernicions, as they are consumed in large quantities: at any rate, the leaves are often recommended as wholesome "salad."-S. R. able to inform "Saul Rymea" that these fowls were [6122.]-POULTRY BREEDING.-I am happy to be [6299.] DISSOLVING SOLDER. Sal enixum, strenuous salt, commonly called sally nixon, for the information of our excellent "Jack of all Trades," is a bisulphate of potassa, and is the residue from the manufacture of nitric acid, by distillation from nitrate of potassa with sulphuric acid.-F.R.C.S. [6239.]-DISSOLVING SOLDER.-Nitric acid will distances from a convex mirror of given radins, we are [6292.]-VARNISH.-Some time ago I was in a similar fix, for having attempted to dissolve white shellac in spirits of wine the same disappointment resulted as to our friend "Jack." I put the bottle away in a warm closet and left it there a long time, when to my great astonishment I found that the shellac had thoroughly dissolved. W. H. C. It is therein hitherto not answered the direct question "W. M. F. P." [6306.]-GALVANIZING BOAT NAILS.-I think the following a more simple mode of doing it than that of "Jack of all Trades." Take 1 part of muriatic acid then till nails are clean; get a basket made of sheet iron and 8 parts of water, put nails into it and sti now and punched full of holes-holes according to size of nails; put them, with a little muriate of ammonia, mixed with them wet as they are, into basket, and dip them into the molten metal. In two minutes they will be all right; |