there will be the same pressure upon it as upon the external air-viz., 15lb. If you put the weight of another atmosphere upon the plug it will be forced 12in. down the tube, but it will require eleven atmospheres, or a weight of 165lb. to press it within 2in. of the bottom. And this resistance is the elastic force of only about seven grains of air! Mr. Rhodes will find his expectations delusive in reference to the air not pressing against the bottle and the metal vessel suspended within it, if he means before the exhaustion of the air from the bottle. If he exhausts the air from the metal vessel there will be an external pressure of 15lb. per square inch upon it, which pressure will continue although it be placed within a bottle and sealed up. Also, the air will press with equal force against the inside and outside of the bottle to the same extent. But if you exhaust the air from the bottle the inside will have no pressure at all upon it, nor the metal vessel suspended within it, and the internal pressure being removed, the bottle has to be sufficiently strong to resist the external pressure, or else it goes in with a crash. J. BUTCHER.

[1056] ON page 142, query 5302, of the present volume, R. Rhodes puts two questions which do not appear to have been answered to his satisfaction, since they reappear on page 250. As this subject has not received much attention hitherto in the ENGLISH MECHANIC I hope to stand excused if I go Somewhat fully into the matter. As to the first question, there is no doubt whatever that if the pressure of the air at the time of filling the bottle was equal to 151b. on the square inch, and the whole of the external air removed, the pressure outwards would be 15lb. on the inch. If only half the external air be removed the pressure from within will still be 15lb., but that from without will be only 74lb., consequently the pressure tending to burst the vessel would be 71b. on each square inch of its surface. Again, if 1-10th of the external air be removed, the uncompensated pressure outwards would be 1-10th or 1lb. per inch. These results are in strict accordance with the acknowedged laws of pneumatics, which are as well established as those of mechanics. As to the second question, why the bottle is not crushed by atmospheric pressure, the answer simply is, that the form of the bottle and the strength of the glass are too great to be overcome by this pressure, otherwise how should we be able to perform our experiments with the airpump, if our receivers, when exhausted, could not bear the atmospheric pressure? As an illustration of this I may mention that wine bottles have been sunk fifty fathoms deep in the ocean and have not been broken, although the pressure inwards must have been 150lb. on the square inch.

The result would be very different if we used square bottles of thin glass. We may obtain at the glass houses what are called breaking squares-i.e., bottles of a prismatic shape-made of very thin glass, and with these we can show both the outward and inward pressure by the crushing of this glass. If, in the above experiment, the bottle be filled with water instead of air, there will be no outward pressure but what arises from the weight of the water, which increases with the depth; but if the bottle be half full of air, or if there be only lin. of air within, it will exert its pressure on the water, and through it on the sides of the bottle, at the rate first mentioned, viz., 15lb. on the square inch, added to the pressure produced by the water.

In the querist's second communication (p. 250), he asks for proofs of this outward pressure. I beg to submit the following:

1. Place a bladder half full of air in a tall glass jar | on the plate of the pump, and place a weight, say 15lb., on the bladder; then, on covering these with a receiver, and exhausting it, the air within the bladder will expand and lift the weight.

2. Place a small bladder, fully inflated and tied tightly at the mouth, under the receiver and exhaust the air; the air contained within the bladder not having room to expand will press with so much force outwards as to burst the bladder.

3. Take a similar bladder and suspend it by a string before a large fire, the heat will cause a tendency to expansion, but as in the former case expansion being prevented the bladder will be burst by the outward pressure.

4. Place two glass vessels, as in Fig. 1, half filled with coloured water, on the pump plate; connect them as in the annexed sketch by a bent tube dipping into the vessel B. The vessel A is closed at the top and contains a quantity of air. This air is pressing outwards with the full 15lb. on the inch, but being counteracted by the atmospheric pressure it gives no indication. Cover the vessels with a receiver and begin to exhaust; at every turn of the handle the air in A expands and forces the water through the tube into the vessel B. When half the air is drawn out of B, the air in A will have expanded to double its former volume, its elasticity is consequently diminished, and the pressure both outwards and inwards being equal, over 74lb. per inch, all motion ceases. One more experiment to show the amount as well as the direction of this pressure, and I

have done.

5. Take a glass tube and bulb similar to the annexed sketch. This is, in fact, a common barometer, Fig. 2. Now the received explanation of this instrument is that the pressure of the atmosphere on the mercury in A supports the column in the tube B-this column becoming shorter when the air is lighter, and longer when it is heavy. Now your correspondent can conceive that the column of mercury may be supported by the weight of the atmosphere, but not by the small quantity contained in the bulb. Place a cork in the bulb A, and it is effectually cut off from the atmosphere, yet it supports, in the same way, the 30 inches of mercury

which on an inch base weighs about 15lb. To make this experiment more complete, remove the cork and fix a small syringe into the neck of the bulb; then, by a slight motion, a small quantity of air will leave the bulb and enter the syringe-the air withdrawn may

not weigh more than the 10th of a grain, and yet the mercury will fall 2 or 3 inches. If the syringe is worked till half the air is withdrawn, the mercury stands at 15in., and if the exhaustion is carried further till, say, 99 hundredths of the air is drawn out, the remaining hundredth part will still support frd of an inch of mercury nearly. In conclusion, allow me to say that pressure is produced primarily by the weight of the air, but also, secondarily, by its elasticity, as in the last experiment. S. P.

IMPONDERABLE FLUID.

[1057] "Z." (let. 953) amazes me that a patent should be granted (October 3, 1866, No. 2536), for discovery of an imponderable fluid. If it deserved a patent it certainly deserves the whole specification presenting in your columns. It seems drawing too much on our credulity to expect any credence to the existence of invisible fluids so very unspecifically "described." Let "Z." state some specific properties attached to it, either as to qualities physical, or as to effects beyond "considerable" and "vital." It ought to be better described. J. BARWICK.

VIBRATION.

any ornamentation, whilst some other of the remarks, would, if strictly followed, convert the Amateur into a Tibbs, a chairmaker in fact; but an amateur can't fill his house full of bookcases and writing-tables.

I think any amateur who makes a pagoda or a vase ornamented by the various instruments in good taste, makes an article the beauty of which is admired far more by the general visitors at his house, than his paintings, statuary, or probably any other ornaments he may possess. And then comes the question, What is a pagoda? Why, says your leader, it is" a Chinese temple, a tomb, a shrine," but of correct architecture. I deny it! A pagoda is to some extent an imitation (of Indian temple), but really is a form of beauty; spiral to some extent, but of no particular school of architecture; simply exhibiting in itself as much variety of turning, of eccentric, elliptic, geometric, fluting, drilling, boring, beading, spiral, medallion (or idol work, see Worcester's "Dictionary"), as good taste, correct form, and beauty of execution will permit.

No one who ever saw the engravings in the ENGLISH MECHANIC of the pagodas (or the pagodas themselves) by the Rev. J. H. Holditch, the "Norfolk Amateur," or Elias Taylor, or of others that could be mentioned, could, would, or did express one word against the style of architecture, workmanship, taste, or beauty; and this was simply because they were beautiful in themselves, and surprised every one by the great ingenuity and perseverance of the amateur, for, as poor Keats said,

"A thing of beauty is a joy for ever." Frequently when showing to visiting friends the work and patterns which can be produced by the geometric chuck, have I been told they are very curious, very beautiful, and immediately have been asked, What are they good for? and though the same sort of remarks as to beauty, &c., of vases, pagodas, with medallions, &c., have been made, the question-the What is it good for?-was not asked.

I find I have gone further than I intended, but I can't forbear asking for a more full and explicit explanation in an early number of "our" journal, of "In what way is an amateur (who, in his enthusiasm for his lathe and the beauty he can produce by it starts work even in winter at seven o'clock, a.m., and frequently, after ordinary people are gone to bed, the second head of the family has to visit his latheroom in evening dress, to recommend him to look at the clock, and to close his workshop),-I would again ask in what way is he to use his expensive instruments, his (not Plant's) geometric chuck (say Ibbotson's), his eccentric and compound eccentric chuck, his elliptic chuck, besides all his cutters, simple and compound, besides other instruments ?" Now what is he to make? I will suggest nothing; but as "Cui Bono" raised the question ("cui. bono," and fixed up some other Latin at the end of the leader, which I omitted to "look in" at the parish clerk's about), I simply require an answer, in what way would "Cui Bono " be satisfied, and what kind of articles suited to exhibit the proficiency of an amateur and his machinery should he make and devise?

I should suppose that even those beautiful and enticing inventions (which are additions to the lathe

as a means of art), the medallion machine of Lowe, the

wood-carving machine of Jordan, the profile-cutting machine of Cunningham, would equally fail in satisfying "Cui Bono" as to what would be worthy of an amateur. To all this I respectfully request an answer, giving such reply in explanation as (if the writer, "Cui Bono," had or has a good amateur's workshop) he would exhibit in fulfilment of "Cui Bono," and merit the motto at the end of the leading article referred to. ARS PROBAT ARTIFICEM.

AEROLITES.

[1061] UNDER "Replies to Queries" (No. 5784) "Castor" asks the origin of these matters or substances, which some suppose to fall, and others think grow.

A friend of mine, residing on the borders of Hants and Sussex, on the chalk range, informs me they have been found 10ft. deep in the chalk in digging a reservoir for water.

My friend is of an observing nature. Perhaps these meteorilites may be found in other strata if looked for; possibly they may have been found. Some suggest these "aerolites" are parts of "exploded planeteolids." If so, would not these fragments or parts show an angular form? Has this ever been noted? On the contrary, do they not have an appearance of a molten shape, as if fire had been directly connected with their formation?

I believe they are mainly formed of iron, which is not magnetic; but there are traces of other minerals.

A few weeks since a correspondent of yours suggested that they might be the "ashen slag" of that gas which has been seen in combustion round the sun. We know the "smoke, gas, or fume" of all the minerals in our earth can be traced in a combustion in the sun's rays.

Iron is one of the most common metals found in our planet. What if Rikart's theory (No. 295, p. 209, 807 of your issue) may be right, and the sun draws a gas from the earth by electro-magnetism, and then burns it? In this case, the gas extracted from iron burnt by the sun would be twice subject to electromagnetic power; how, then, can we expect to find any magnetism in the slag ash or refuse? But hence arises another question-perhaps a new one. Are new ideas or questions at once to be rejected? This question is, if the sun's attraction is one of gravitation

THE ENGLISH MECHANIC COLONY.-No. II. [1062] HAVING studied this part of the subject referred to in my letter 950, p. 281, with very great care, in conjunction with those who have already joined me through the influence of your journal, we have come to the conclusion that Tasmania possesses every possible requisite for the establishment of such a colony.

Australia proper possesses unlimited resources, mineral, agricultural, and pastoral, and in the course of time no doubt many industries will take a considerable hold; but as a rule its climate is not suited for the general development of mechanical or manufacturing industries, the extremes of heat being too great throughout its whole extent. Hence there is no doubt but that the vast supplies of wool, cotton, sugar, silk, &c., which Australia is capable of producing in enormous abundance, must find their way to a more temperate clime for the purpose of being worked up into their destined products, and in the whole of the southern hemisphere putting aside New Zealand which in the mean time is too distant-Tasmania, is the only spot of earth possessing the whole necessary qualifications for such a purpose.

the latter is likely to play a very important part in the future history of the southern hemisphere.

Guided by those considerations, and the advice of my colleagues in this movement, I have drawn up a careful résumé of our object, and submitted it to the agent for the Government of Tasmania, who has forwarded it to his government for consideration, and I expect there will be an answer in the course of January or February next. There can, I believe, be little doubt but that a very favourable view will be taken of the movement, and that liberal terms will be secured. In the mean time it is advisable that immediate steps should be taken to set the project fairly in motion, and in order to accomplish this satisfactorily we should have the co-operation of a few additional parties of influence-in different sections of the country -who would be prepared to promote the interests of the movement in their respective districts.

My proposal is that the first contingent of emigrants should consist of at least 1,000 persons. So that there will be ample room for a few educated men, Bay two or three clergymen of the Episcopal and Presbyterian churches, one or two additional medical men, at least one young and energetic lawyer, who could immediately engage himself in drafting the regulations which are to guide us, and such selections of handicraft as would at once form a working community. The prominent idea is to establish a young community embodying all the essential elements of society at home, so that your numerous readers-all intelligent I may easily assume-can readily determine for themselves what sort of qualifications are required, and I take this opportunity of calling upon them to lose no time in tendering their assistance. I have no doubt even that there are many of the fair portion of your readers who could be of great service, and the offer of their assistance would be especially acceptable. To those of your readers who may be in possession of considerable means, all but useless in this country, and who contemplate embarking their energies and capital in some more fertile field, I would point out the probable advantages attainable in connection with such a movement, not only in the better and more The whole island is well watered by numerous rivers profitable investment of their capital, but also in the the principal of which take their rise in some half-prospective honours which may await them in becomdozen lakes situated in the interior at elevations varying the successful leaders of a systematic plan of emiing from 3,000 ft. to 4,000ft. above sea-level. Nearly gration, which is to become a permanent source of the whole coast-line is indented by innumerable har happiness and prosperity to thousands of fellow bours and inlets; so that, as will be surmised, the beings. general scenery is of the most charming character.

This beautiful island, which is nearly as large as Ireland, or about equal in extent to the kingdoms of Belgium and Holland coujoined, is situated between the parallels of 40 and 43 south, at the southern extremity of Australia, from which it is divided by Bass's Straits, about 120 miles in width, being exactly opposite to Victoria, at present the most enterprising and progressive of all our southern colonies.

The island is said to unite in its general character the climate of Italy with the beauty of the Apennines and the fertility of England. Mountain and valley, hill and dale, crowned with towering forests, and rich pasture grounds in the plains, afford the most pleasing variety.

The natural productions are much the same as those of Australia proper, but with a vastly more temperate and equable climate. The colonist has no cause to fear the dreadful droughts, the storms of blinding sand, the overwhelming floods, nor the devastating hurricanes which so frequently exercise their pernicious influence on the Australian main, and constitute the only drawback to its splendid attractions. The extreme salubrity of the climate of Tasmania is best seen in comparison with that of other well-known places:

It will be seen by an examination of these data that the climate must be remarkably healthy, and this is proved by the fact that annually, on the approach of summer, hundreds of families, escaping from the hot winds of Australia flock over to Tasmania, in order to enjoy its more genial atmosphere and its brilliant sky. I need scarcely point out that a territory so favoured, with its noble mountains and its fertile valleys, its magnificent forests, its inexhaustible lakes which feed its 1,200 miles of rivers, not to speak of its extensive and often well-sheltered coast-line, in conjunction with a climate not excelled in salubrity by that of any other country, must possess immense powers of production, both animal and vegetable, and it is found that the results fully bear out this assumption.

Tasmania is already known to possess in abundance many of the most useful minerals and metals, such as coal, iron, copper, lead, &c. Gold also exists to a workable extent, so that its mineral resources may be said to present quite as favourable an aspect as those of the animal and vegetable kingdom.

I have been thus particular in pointing out the peculiar climate and resources of Tasmania, in order to show the close similarity in its relations to Australia and the whole of Polynesia it bears to Great Britain in the latter's relations to the more southern parts of Europe, and those other countries of the northern hemisphere less favourably situated for the prosecution of manufactures.

When we consider that a very large portion of the continent of Australia is intertropical or subtropical, having therefore a capacity for the growth of cotton, sugar, silk, coffee, wine, tobacco, &c., in great abundance, and that no doubt, in the course of time, those products, by means of intersecting railways converging upon Melbourne, can be brought within 150 miles of the shores of Tasmania, it will be seen that

I trust that this appeal will be successful in bringing a large number of additional sympathisers to our aid, as it is only by such combined action that an undertaking of this character can be carried to a successful issue; and if we consider the tremendous competition, not only in every branch of business, but also in the investment of capital in the mother-country, in contrast with the splendid fields of enterprise calling loudly for us in our colonies, of which, I believe, I have pointed out the chief, the result of this appeal cannot, I think, remain doubtful. I trust that you will consider my letter of sufficient importance and interest to deserve a space in

your columns.

ALEXANDRA.

I heartily concur in the above.-FRED. ROW, M.D.

LUNAR COSMOLOGY.

It is difficult to picture to the mind the extent of this vast formation, which (by way of illustration) would contain our own metropolis about 16 times, and

whose depth is insignificant, compared with its superficial area of 2,500 square miles.

The apparent total absence of a medium capable of dispersing light is striking here, as when traversed with the horizontal rays of a rising sun, untempered by any cloud, the telescope shows the whole of this vast landscape to be steeped in total darkness.

Most descriptions of the lunar surface in my opinion tend to convey an erroneous impression as to the actual proportions and dimensions of objects, depicting the character of the scenery as consisting of a vast collection of crater mountains or volcanoes, thus giving an abnormal character to lunar formations, which appears unwarranted by observation.

The character of these formations, considering their proportional dimensions, is totally different from that of the terrestrial volcano; volcanic forces have, no doubt, played their part in their production, which is indeed inevitable in the accomplishment of any extensive change of surface.

It is not my intention to attempt to form any conclusions on this subject from mere speculation; careful observation combined with proper judgment, and the attainment thereby of a knowledge of the true forms and sections of lunar objects, are the only data on which any reliable theory can be based.

The lunar formation of which a section is given, forms an extensive tract, 56 miles in breadth, being considerably greater in extent than an ordinary terrestr landscape. A spectator stationed in the centre would observe the highest point of the so-called ring at an angle about 41 above the level of the interior, an inclination so slight that I think it may be safely said that it could with difficulty be distinguished from the horizontal in the absence of an angular instrument. If the interior slope of the so-called ring (extending to about one-third of the breadth) may be taken as an approximate type of that existent in other lunar for mations of the same character, and which do not present the somewhat peculiar feature of "terraced slopes, the gradient is found to amount to about one in ten, apparently but slight for the interior of a crater, this inclination not being extraordinary on a turnpike.

An example of a terrestrial volcano may serve to show the contrast of relative dimensions in a clearer light: for this we may select Etna. In this instance, although the height of the crater wall is approximately the same as in the lunar formation, the breadth of the crater is so utterly insignificant in comparison that it would probably be invisible if placed on the moon, and the whole mountain would probably rest with safety on one of the "terraces" of Copernicus, whose width, roughly estimated according to scale, amounts to about two miles; and the improbability appears still more palpable to consider the extensive lunar formation to have ever served the purpose of a crater in the ordinary sense of the term, i.e., subject to periodic eruptions.

Taking due account of the relative dimensions, slopes, &c., which form the physical character of these lunar formations it appears to follow, as a logical inference, that there is little or no analogy between the lunar objects and terrestrial craters. The former (I do not insist on Copernicus in particular, its terraced character being at least somewhat exceptional) appear to resemble vast tracts surrounded by land rising gradually to a higher level, such elevation being inconsiderable compared with the superficial area. we make the supposition that they are clothed with vegetation, a similar physical distribution of land on our own globe would not, I would venture to state, appear anomalous, if, indeed, a configuration of a strata of a somewhat similar character as to cross section does not actually exist.

I have in this letter endeavoured to interpret observed phenomena, avoiding all baseless speculation, and I would protest against the use of the term "crater," as tending to stamp the character of these lunar formations, its applicability being at least open, as I have endeavoured to show, to strong doubts. Such designations when misapplied, tend rather to discourage future investigation. S. T. PRESTON.

MOUNTAIN SPRINGS.

[1065] THERE are some very simple and some rather knotty questions inserted in our valuable paper time after time, and most of them get answered, to the general good of the subscribers. May I venture to put a question concerning those beautiful springs all over England?

These springs meet the eye in almost every direc tion-far away in the uplands and lowlands they are to be found. I can well understand in the latter, the water issuing from any outlet in the strata of rock, how the surrounding uplands contribute to the supply. But in a range of hills, or hillocks, from 1,000 to 2,000 yards long, and from 100 to 500 feet from the level, with a very narrow strip of tableland above, or with hills of conical shape, it is different. Half way up the incline from foot to brow of these hills there is the little spring rippling year after year, and scarcely are these springs known to dry up in a generation. It is a fact water will find its own level. But surely here the rocks above are not sufficiently charged to keep up the continual supply, without some force from below. If some one of those gentlemen who have studied geology would kindly favour me with an explanation of the source and force of these springs, I should feel thankful.

ADAGIO.

I have made it in Kilmarnock, in 1842, for the illumination when Lord Eglinton was married. The burner only requires to be balanced on a small pointed steel wire soldered on top of the inner tube, and the oil poured into the outer tube to make the gas-tight joint. The reason oil is employed is that water soon dries up and the gas escapes. Any further information I will give if required.-J. M.

[5192.]-ORCHIS (U.Q.).-Most of this family are tropical plants flourishing in the hothouse or damp-stove. Why not try some of the ferns? Adiantum capillus Veneris, Polypodium dryopteris, P. vulgare, and several others, will grow in a hollow piece of wood or cocoa-nut shell. Fern collectors are plentiful, and for a few pence will supply suitable plants.-ESURIENS.

[5218.]--ON HEATING SURFACE OF BOILERS (U.Q.). -The following are the proportions per horse power of a 10 horse-power portable engine. Firegrate, 70 square inches; sectional area of tubes, 15 sq. in.; effective heating surface, 75 square feet. It will, I think, be found that in general the proportions increase somewhat in the smaller sizes, and decrease in the larger ones: thus, area of grate, say, 1 square foot; sectional area of tubes, 30in.; heating surface, 15ft.; number of tubes, 40; diameter of tubes, lin. inside; diameter of boiler, 18in.; length of boiler-barrel, say, 2ft. 6in.; thickness of plates not less than fin.; pressure of steam 50lb. The boiler will bear 150lb. if properly made.-No. 170.

[5248.]-THE RIPENING OF PEARS (U.Q.).-Due probably to difference of temperature; perhaps also to less amount of carbonic acid gas.-M. P.

[5253.]-SILVER COIN.-A coin of Henry V., Emperor of Germany (1106 to 1125).-BERNARDIN.

[5262.]-SIZE AND POWER OF BOILER (U.Q.).— Bofore replying to this query, "G..V. R." must state what power he wishes to get from his engine, and what pressure per square inch he would like to use, as the size and strength of his boiler must be determined accordingly. I may, however, say that 2 horse-power is the utmost that should be attempted with cylinders of the size given, and a boiler for this power may be arranged on the proportions given.-No. 170.

[5293.]-CEMENT FOR LEATHER (U.Q.). Pare down to a thin edge the leather ends; when perfectly thin, heat as much as you dare without risking damage to leather; melt glue in a ladle and apply to the hot surfaces of the leather; put in press until cold.-GODSTONE LABORATORY.

[5293.]-CEMENT FOR LEATHER (U.Q.).-See pp. 812, 464, and 486, Vol. X.-SERGIUS.

[5306.]-FLEXIBLE WRITING SLATES (U.Q.).—I believe they are cardboard with lamp black painted over.-IOTA.

[5307.]-BLACK JAPAN (U. Q.).-I suppose the pitch spoken of by "H. w. R." is meant to be asphaltum. This is simply dissolved in mineral naphtha.-Tнos. HARDING.

[5307.)-BLACK JAPAN (U. Q.).-Until within a few years, Messrs. Harland & Son were supposed to be the sole possessors of the secret for the manufacture of this. Theirs is still the best, though Messrs. Noble & Hoare's is almost as good, if not quite. It is a tedious process, and to make it successfully would require a page of the ENGLISH MECHANIC to explain it.-GODSTONE LABORATORY.

[5869.]-INSTANTANEOUS PHOTOGRAPHY (U. Q.). -You would hardly succeed. Prepare a new bath; increase strength 10 grains per ounce; increase strength of iron developer; and then, if you have quick acting lenses, you may succeed in getting a perfect picture this time of year now and then for a treat.-GODSTONE

LABORATORY.

[5869.]-INSTANTANEOUS PHOTOGRAPHY (U. Q.). -If "A Farmer" will purchase the "Photographic Tourist," published by F. J. Cox, Ludgate-hill, price 1s., he will there find the information he seeks.-THOS. HARDING.

[5384.]-RESPECTIVE MERITS OF TELESCOPES. By a strange obliquity of mental vision, "B." credits me with a statement exactly the reverse of my last communication. Instead of stating the telescope did no better with a power of 20 and clear object-glass than it did with high powers in a fog, I said that when bearing the strain of high powers at a time when the object-glass was like ground-glass from condensed dew, the clearness and sharpness of definition of Jupiter's belts and minute objects on the moon was the same as when viewed with a power of 20 and clear object-glass. I do not suppose it is equal to higher-priced glasses of the same aperture, but consider that its performance for solar or lunar observation, or defining needle-points of light with low star power, or the stereoscopic views of the nebula in Orion with high powers, and the persistence with which it pursues the faintest traces of the outflowing streamers, or its terrestrial performance, each and severally as worth far more than its cost. The 250 power used is sent out by Messrs. Solomons as such; the 800 belonged to another telescope.-AMATEUR.

discs can be obtained already ground and smoothed; this, I believe, has always to be done by the optician, although any glass-grinder could do the work just as well.-W. PURKISS.

[5423.]-TURNER' SCEMENT (U.Q.).--Collins's mastic glue, a mixture of asphaltum and gutta percha, does very well for this purpose. It can be bought at any leather shop.-A. S. C.

mended by Mr. Vallance in Vol. II., p. 34 (Feb. 1864, with illustration), but slightly Astronomical Register, modified. A the polar axis of 1" pipe, and rotating in the two metal straps fixing it to E. B the declination axis 1", on which the telescope D, rotates by the central aperture in the cradle C. E block of hard-wood cut to the altitude of the pole (= latitude of place) and grooved out to the diameter of the pipe. F horizontal block of wood to which E is firmly screwed or bolted, and which has a notch where the polar axis bears, with a thin plate of iron slightly larger than the diameter of the polar axis for it to work on. F is firmly fixed to the upright of the stand, which may be a conical tube, as advised by Mr. Blacklock in a recent number, or a 4" or 6" iron pipe with flanges at the ends, one of which (if bolted to a flag the better) is firmly fixed in the ground, of course perpendicular; or it may be attached to an ordinary tripod stand. All the wood should be painted or varnished, as also all the ironwork, except the bearings. G the counterpoise screwed to the end of the declination axis, or fixed by a clamp screw from the side. The cradle C is shown in elevation and section, at G, to show the mode of fastening the telescope to the cradle with clips of thin sheet brass or iron, which admits of the telescope being detached by unscrewing the nut heads; the cradle is prevented from slipping on the axis by two or three pins fastened in the pipe, and the telescope is clamped in declination by the nut screw on the end of the pipe, half a turn of which liberates or clamps it. The nut must have two or three pins 2in. Sin. long, inserted round the circumference to avoid the use of loose screw key: The polar axis and the declination axis (in two lengths) are firmly screwed into the T-joint; another T-joint with the thread filed out forms the rotatory part of the cradle; the upper part must be cut open in the direction [5421.1-MICROSCOPE (U. Q.). "A Scientific of the length, and flattened out, and the other part Novice." The powers of Field's 10s. 6d. Society of riveted, screwed, or bolted to it. Fig. 2 is another form Arts School Microscope, as given by Mr. H. Woodward of mounting, it is constructed of two ordinary pulley in his work on the "Prize Microscopes" is :-No. 1, 6 dia- driving wheels of about 12" or 14" diameter, one rotating on meters, or 36 times in superficial extent; No. 2,8 diameters the polar axis 3 forms the hour circle; the declination or 64 times superficial; No. 3, 10 diameters or 100 times axis is a rod of iron, the end firmly screwed into the boss superficial:" and he also remarks, "Nos. 1 and 2 together of the wheel (the deeper the boss the better, usually give 18 diameters, or 169 times in superficial extent; about 3in.), and projecting beyond the circumference Nos. 1 and 3, 16 diameters, or 250 times superficial; of the wheel sufficient to carry the declination Nos. 2 and 3, 20 diameters, or 500 times superficial; and wheel and the nut, a corresponding one for the Nos. 1, 2, and 3, 26 diameters, or 676 times in superficial counterpoise being attached opposite, and both extent. The focus you must determine for yourself; any work on optics or the microscope will tell you how. You can get a catalogue of mineral collections, priced, of Bryce M. Wright, 86, Great Russell-street, Bloomsbury, W.C.-THOS. HARDING.

[5401.]-BRAZING WITH BLOWPIPE (U. Q.).-Use spirits of wine (methylated will do though it smells unpleasantly) and add as much paraffine or turps as you can without causing the flame to smoke. If in a workshop, with funnel or hood over, plain par fine is excellent. GODSTONE LABORATORY.

or

SC: ewed or riveted to the circumference to keep them steady. 2, the declination circle clamping the same as in Fig. 1, and on which two pieces must be fixed to carry the telescope, or this wheel may be dispensed with by making the cradle as in Fig. 1. 3, the polar axis is firmly fixed to the altitude block by the straps, and the top is accurately turned to fit the opening in the boss of the circle, a nut screw at the top to prevent the mount

open at one end; the smaller one about Sin. less diaof two cylinders of tinned iron (if japanned better), meter to prevent friction. The bottom one is nearly filled with water, and the top one has a small gas tap to regulate the emission of the air, and also a 1" screw valve to allow the rapid admission of air when being lifted up for use. The speed can be regulated both by the aperture of emission or by addition of weight on the top. The addition of weight is perhaps the best, 43 the ratio of the diminution of weight by the immersion of the cylinder in the water is diminished. The form may be varied according to the requirements of the case, being made long and narrow, or short and broad. The motion should be communicated to the telescope by the hour circle or a sector clamping to the polar axis, as if the cord is attached to the eye end, and the emission regulated to the equator, the rate will be too great fcr an object nearer the pole, as it will cause the telescope to sweep through a great circle in 24 hours, whereas the circles described by objects off the equator are smaller than great eircles diminishing to nil at the pole. The drop in relation to the time required may be regulated by combinations of pulleys so as to give a drop of 1ft., 2, or 3ft. in one or two hours or more. It can also be attached to the ordinary tangent screw of the toothed hour circle instead of a clock. The only drawback is the water freezing in winter; if some suitable liquid that would not freeze or thicken too much in frost could be used, this would be remedied. I hope these hints may be of service to some of your readers, and no doubt many with lathes and other means of construction will be enabled to make superior mounts, these being a simple as possible in construction.***.

[5588.]-CONTRACTED JOINT.-I have always at tributed the stiffness of the joints of the feet and toes to the heavy and inflexible boots worn by country and labouring-men. When the soles are plated with iron or made of wood, as they sometimes are, it is impossible to bend the foot in walking, and after long wearing these clogs to locomotion, the joints become stiffened from want of use. I have known men to recover in some degree by wearing lighter and pliable walking, shoes, frequently bathing the feet in warm water, and rubbing and bending the joints.-ESURIENS.

[5606.]-COLLODION BALLOONS.-Get a Florenca flask size of balloon required; pour in it some collodion and let it run evenly round the sides; when one layer is dry repeat it until a pretty substantial coating is formed on the sides of the glass. Then separate a small portion of the collodion from the glass; and by blowing under it and carefully manipulating, it will become detached and can be withdrawn from the flask. The flask may be broken instead. I don't know if this is very lucid. Perhaps "Urban" will teach us some better way. I learnt it from Frankland's assistant.-A. H. N.

[5606.]-COLLODION BALLOONS.-I have just come across the following in Bloxham's "Chemistry," p. 508:-"Collodion balloons may be made in the following manner:-6 grains of collodion cotton are dissolved in a mixture of 1 drachm of alcohol (sp. gr. 835) and 2 The solution is poured into a dry Florence flask, which drachms of ether (sp. gr. 725) in a corked test-tube. is then turned about slowly, so that every part of its surface may be covered with the collodion, the excess of which is then allowed to drain back into the tube. Air is then blown into the flask through a long glass tube attached to the bellows, as long as any smell of ether is perceptible. A penknife-blade is carefully inserted between the flask and the neck of the balloon, which is thus detached from the glass all round; a small piece of glass-tubing is introduced for an inch or two into the neck of the balloon, so that the latter may cling round it. Through this tube air is drawn out by the mouth until half the balloon has left the side of the flask, and collapsed upon the other half. By carefully twisting the tube, the whole of the balloon may be detached and drawn out through the neck of the flash, when it must be quickly untwisted, distended by blowing through the tube, tied with a piece of silk, and suspended in the air to dry. The average weight of such balloons is two grains."-A. S. C.

[5610.]-WHEAT.-The northern limit of wheat in the British Islands is as far north as the parallel of lat. 58 deg.; in Sweden and Norway, 64 deg.; and from 40 deg. E. 'long., in Russia to 140 deg. E. long.; in Siberis the limit is, with very slight variations, at 60 deg. N. lat. There can be little doubt, I think, as to the accubeen cultivated in Norway further north than lat. 64 racy of Dr. Schübeler's assertion that wheat has not deg. 40m. As to Keith Johnson's "Atlas," there must surely be some mistake if the line of limit in Europe does not extend further north than lat. 58 deg., since wheat is cultivated in considerable quantities in the south of Sweden.-S. . . . R.

[5621.]-SNUFFLESS CANDLES.-I think it will be found on inquiry from an intelligent candle-maker that the thickness and sort of wick tre determined by the fusibility of the tallow, wax, or other material. A rushlight has a small amount of tallow because its wick does not possess the power of imbibing by capillary attraction much fluid. A tallow candle with a wax-candle wick would gutter.-M. P.

[5627.]-FASTENING LEATHER BANDS.-Marine glue will fasten then if the ends are pared off and well pressed together. I have sometimes driven a single rivet bands I prefer lacing with thongs, although not so neat through as an extra security. For very broad and long a finish.-ESURIENS.

he requires. If "H. A. L." will explain how 800 footpounds can express a force of 4,8461b. through 4in., or, as I read it, 1615-33 foot-pounds, I shall feel obliged.C. W. STIDSTONE.

[5666.]-ISOLATING PORTION OF SUN'S DISC.In reference to the remark of "F.R.A. S.," in his letter, page 273, I may state that the idea of the revolving diaphragm was original as far as I am concerned, and suggested itself to me as I was rotating the diaphragm of my microscope, after having just read some hints on the best mode of observing the eclipse of the sun. I have no chance of seeing the volume he kindly refers me to in an out-of-the-way place like Carmarthen, whence I write.-L. C. E.

[5687.]-FUNGUS IN WARDIAN CASE.-To this a reply has been sent, which the querist will not accept as a sufficient reasor. Having grown plants under shades and in cases for twenty years I may remark that it is exceedingly difficult to keep in the same case plants of different families, as, for instance, ferns and cacti; the degree of light, moisture, and ventilation that may suit one proving noxious to the other. By constant attention I have succeeded in growing together plants of very diverse habits, but I cannot recommend the plan; mould is almost sure to make its appearance in some of them.-MEUNIER.

[5687.]-FUNGUS IN WARDIAN CASE.-I have no doubt my statement as to want of ventilation and excess of moisture is correct if you will examine. Small shades do without ventilation in places where there is a great variation of temperature. The great evaporation and condensation on the sides of the glass will compensate for ventilation to a certain extent.-T. F. [5704.]-GAS.-I beg to thank "Garde le Roy" for his reply to my query. I have plenty of time to attend to it, and do not mind the trouble. I should fix the retort in the furnace I work at. The expense of heating it will be nothing. I can also get plenty of gas-pipe and fittings all sizes in exchange for their weight of our scraps of iron. I have also good coal at 4s. 24. per ton. I meant by two lights two single jets, but four would be better. I shall be glad to receive "Garde le Roy's" reply to my query, with size and sketch, if possible, of the apparatus I shall require. I beg also to thank "Ben G." for his reply to my query.-J. M.

[5719.]-WELSH GROIN.-I think "E. L. G." will find that the term Welsh is derived from the German for Italian. Why Italy should be called Wälschland or Welshland is an ethnological question of some interest. Wilsch, also, means in German, foreign, outlandish.-M. PARIS.

[5716.]-STEREOSCOPIC LENSES.-I submit that "E. L. G." is here quite in error. Stereoscopic pictures are always in wrong perspective, the parallax being exaggerated. This very exaggeration causes the appearance of relief to be greater than ever seen in nature. The size of the pictures cannot be material. This observation does not, however, affect the possibility of the combination sought.-M. PARIS.

[5748.] CUPRO-AMMONIUM-Rub together sulphate copper loz., and sesquicarbonate of ammonia 14oz., till carbonic acid is no longer evolved. Wrap the mass in bibulous paper and dry it in the air.-J. W. C. [5755.]-POLISHING SPECULA. In answer to "G. C.," p. 261, I may tell him that the squares of my grinding-tool are all uniform in size, so that when the figure of the tool is correct the finest grinding does not, nor should not, show any sign of unequal polish. In the polishing, however, I generaly find that the polish advances more rapidly in the centre of the mirror than elsewhere, but this helps rather than prevents the attainment of the parabolic curve.-W. PURKISS. [5757.)-FIXING GUDGEONS IN WATER WHEEL SHAFTS. In reply to this query, p. 308, for curved end of gudgeon read turned end.-MEUNIER.

[5781.]-WORKING BATTERY.-What Colonel B. requires is a commutator, and if he will say whether the reversal is to be made by hand or self-acting, I will send the drawing and description of a plan suitable for either way, but to manage what he wants properly the wires from the battery to the magnets should be otherwise arranged.-UN ÉCOSSE.

[5784.]-AEROLITES.-Aerolites or meteoric stones are attributed by some persons to terrestrial, and by others to lunar volcanoes. They have also been supposed to be concretions formed in the regions of our atmosphere, whilst others have considered them as small planets revolving about the sun or earth, which, coming in contact with our atmosphere, take fire from the resistance and friction which they meet with in passing through it. Since the discovery of Sir H. Davy, that the earths are metallic oxides, it has been suggested that the bases of the earths may originally exist in the meteor in a metallic state, and that when the body arrives within our atmosphere a sudden and violent combustion is produced by the streng affinity of these metals to oxygen.-BEN. G.

[5811.]

PROOF-About two years ago we had occasion for a MAKING WOOD PARTITION SOUNDsmall committee-room to be made off one corner of a general reading and news-room. We simply made two partitions about 8in. apart, and two doors, one to open in, the other out, and I can only say it acts admirably. I have sat in the news-room for above an hour at a time, when the room has been occupied, and I have not known there was any one in until I have seen theta come out, the sound has been so effectually stopped.-GOOD

WORDS.

[5811.]-MAKING WOOD PARTITION SOUNDPROOF-Supposing "Whisper's" wood partition to be 6in. thick, if he fixed a fillet 2in. wide up the centre of each stud, and nailed laths to the fillets between the studs, covering them with a cost of plaster, and then proceeding with laths and plaster (in the usual way) on the edges of the studs, thus leaving three spaces instead of one, and having four separate thicknesses instead of two, he would find this to answer the purpose very well; nothing less than the report of a gun can be heard through.-F. B.

[5819.]-GUN QUESTION.-The bullet WAS not wrapped up in anything, and the same wadding was used in both cases, and the weight of shot and bullet about equal. I have tried the experiment both with smooth bore and rifle. "A. S. C." Perhaps this gentleman will allow me to say that the question suggested itself to me by actual experience, not by books.-SERGIUS.

[5840.]-LIQUORICE.-I send the following, taken from "The Vegetable Kingdom," by William Rhind: Blackie & Sons, Glasgow:-Liquorice is a native of the south of Europe, and appears to have been cultivated in England since the time of Elizaeth. The chief places where it was long reared in any quantity for sale were Pontefract, in Yorkshire; Worksop, in Nottinghamshire; and Godalming, in Surrey. It is now, however, raised by many gardeners in the vicinity of London, by which the London market is supplied with roots in no respect inferior to those of warmer climates. It requires a deep sandy loam, trenched by the spade or plough to 2ft. or Sit. deep, and manured if necessary. The plants are procured from old plantations, and consist of those side roots which have eyes or buds. The planting season is either October or February, and March; the latter is preferable. The plants are dibbled in, in rows 3ft. apart.

apply at the Royal School of Mines for their rules, &c. There are, I believe, several scholarships. It would be too much to give all particulars in your paper.-A. H. N.

[5855.]-STOPPING AND FRENCH POLISHING.— "Plaster de Paris" is used by most French polishers to fill the pores of new wood, and is made by mixing it to a paste and applied immediately by dipping a piece of cloth or a rubber of linen rag, and covering the whole surface. The polish you refer to is called spirit polish, and is applied with a brush used mostly for carved work, &c.-F. B.

[5856.1-QUILTING.-Tack three corners of the quilt to the floor like a carpet, roll it up as tight as possible from the other corner to the middle; one-half of the quilt will then easily go under the arm of a much smaller machine than a "C" Howe. Pull tight while rolling and the quilt will be as free from puckering as if done in a

frame.-ScoTCHMAN.

[5856.] QUILTING. Manufacturers use light machines of all kinds for quilting. When the stitching is required some distance from the edge it is folded, an operation taking time, and troublesome of course. To avoid this would require a machine longer than any in use. It could be made to order, but at increased expense. Thomas's machine for tailors, with long arm, could be had new or second-hand.-A PRACTICAL MAN.

[5857.]-WATER-WHEEL.-I think a turbine would be the best, as he has back-water; they are also cheaper at the commencement than a water-wheel, and cost less for repairs. Messrs. Williamson Bros, have made one for us and several others in my neighbourhood, which are well spoken of.-JNO. Wild.

[5857.]-WATER-WHEEL.- Turbines are more in use, I believe, abroad than here, and the information I have myself collected on the subject is very contradictory as to their efficiency. When working under extremely high falls they seem to answer well, and if of moderate size on low falls also; but when of considerable size and on medium falls (say 20ft. to 30ft.) I think they are not so satisfactory as a good overshot wheel. Gwynne & Co., of London, and the North Moor Foundry Company, Oldham, are makers of different kinds, and Í should recommend "Vivis Sperandum" to write to both. A turbine is less affected by back-water than an ordinary wheel.-L. C. E."

[5864.]-WATER POWER-Not if they are of large size; the power would be but small in your case.L. C. E.

[5865.]-SULPHURIC ACID-As sold at the ordinry druggists is tolerably pure; but "J. W." would do well to test it as to strength and purity if he requires it for any delicate purpose. Methylated spirit will make ether, chloroform, &c., &c.; for some purposes answers very well.-A. H. N.

[5878.] - SPRINGING LEVER WATCH. - TO usual, and by judiciously bending the innermost turn. "LEARNER."-The spring is pinned on the collet as is set perfectly concentric, at the same time perfectly true in flat with the balance on which it acts. The outside turn must not touch the curb pins in any part of side to the other. A "lever" balance, if it vibrates the progress of the regulator when pushed from one more than a turn, ought to be in perfect poise. The the crossing over on the upper arc of the vibration will making it heavier on one side will have no effect, for counter-balance all the effect on the lower arc.-No

[5878.]-BOOKBINDING.-First get a frame, or get two pieces of wood 1ft. long by lin. square; fasten them to a table a foot apart; then screw a piece of wood at the top of the up-posts; then fasten your bands, as many as you want, on the book. First get your numbers together, and beat them with a heavy hammer (face 3 in. diameter) so as to make them solid. Then get your book or numbers together, fasten them in an apparatus so as to fasten tight, then saw three grooves in 1-16in. to let the bands rest in; then place one number (the last number down first), put your needle in at either end, and put it at the first side of band, press it through the number, then put it back at the other side of the band, and the two other bands same way. When you have got to the end put it through the number, not round the band, so as to go up to the other number. Take your other number and start at the end you leave off. One thickness of thread at a time.-A. WILKINSON.

299

[5776.]-WOOLLEN RAGS AND SHODDY.-Vide p. of the "Waste Products, &c.," by P. L. Simmonds (London, R. Hardwicke, 1852); very interesting particulars on that industry.-BERNARDIN.

(5776.]-WOOLLEN RAGS AND SHODDY.-Some thousands of tons of rags are collected in England and thousands more imported. In the manufacture of shoddy, the careful cutting and sorting and the proper classification of the various qualities of rags is the most important stage; for this great experience is required. The mechanical department is supplied by washers, rag-tearers (vulgarly called a devil), and scribbling engines. The washer is of the same description as a flock engine or grinder. The rag-tearer consists chiefly of a large cylinder, the surface of the circumference of which is covered with teeth, spiked coarse or fine, according to the rag to be torn. The scribblers are machines used in opening wool. The price of woollen rags depends upon the precise kind of woollen rag, from £5, with intermediate prices to as high as £70 and £80 per ton are given. The manufacture of flocks and mill-pulp is generally, I might say always, carried on with that of shoddy. In Yorkshire shoddy mills are legion; in Gloucestershire there are many.-A SHODDY MANAGER.

[5778.]-OAK GRAINING.-The colours required for oak graining are burnt umber (in oil) (a piece about the size of a pigeon's egg will make a pint), boiled oil, gold size (about three tablespoonsful), and turps. The tool required is a piece of leather about fin. thick, 2in. wide, and 8in. or 4in. long, with notches cut on each edge; draw this over the work and then comb with grainer's combs of different size, and a brush. To put the "flower" in, all that is required is a piece of linen held over the thumb nail, and rub where you intend they shall be. A good plan is to get a piece of natural oak and copy from it.-F. B.

[5778.]-GRAINING.-See p. 240, Vol. X.-SERGIUS.

[5879.]-WATER POWER.-A turbine unquestion

[5844.]-BOILER EXPLOSIONS.-Will "M. P." say what he means by "the lowest stratum of water being lifted from the plates by a sudden increase in the evolution of steam?" If he is writing of a tubular boiler, why does he say the bottom of the boiler becoming red-ably.-L. C. E. hot? I can understand the top of the tubes in a Cornish boiler getting hot; but the bottom plates of a boiler without tubes fired underneath, I think could not get red-hot unless it was empty. If the water was allowed to get very low, the side plates of boiler above the water would get hot, and if cold water were then to be run in the boiler, why I should like to be at a distance. But the lowest stratum of water would not be lifted by any sudden evolution of steam, for if the water was low, and the plates above get red-hot, they would be so weakened that the then-existing pressure would burst them before any sudden evolution of steam could take place.-FRED. ROE.

[5846.]-CARBONIC ACID v. CARBONIC OXIDE.The cause of death was, as stated at the inquest, carbonic acid. Carbonic oxide is not one of the products of the combustion of charcoal in ordinary air, but is the product of the combustion of charcoal in carbonic acid; therefore, in the case in question, death would ensue from the inhalation of carbonic acid anterior to the generation of carbonic oxide.-S..... R.

[5846.]-CARBONIC ACID (Dioxide) v. CARBONIC OXIDE (Monoxide) were probably both instrumental in causing death. The former, though heavy, would soon become diffused through the room.-A. H. N.

[5849.]-BOOKS ON WATCHWORK.--TO "COMPEN SATED BALANCE."-I do not think either of the books mentioned can be procured but through a foreign bookseller, who could also get to know the prices, which I believe would be about £1.-NOBODY.

[5851.]-QUARTER BELLS FOR CLOCK.-I think

the best place for small bells in London is at Mr. Drury, clockmaker, Caledonian-road, King's-cross,--CLOCK

[5883.]-COTTON SPINNING.-I have seen the old worn out buffalo-skin boxes that are used about a factory boiled down and made into cakes like glue, and laid aside, and when required for use these cakes are dissolved in a common glue-pot and applied to the surface of the rollers with a brush, like varnish. It is generally done upon Saturday, after the works are stopped, when the rollers are taken out of their places and allowed to dry till Monday morning.—VALVE.

jects for examination are set in Latin, English grammar
[5884.]-EXAMINATIONS FOR SURGEONS.—Sub-
and history, Euclid (books 1-2), arithmetic and algebra,
Greek, French, German, mechanics, chemistry, botany,
aud zoology. The last seven are not compulsory, but
"Young Man" will get
one at least must be chosen.
the particulars and the examination papers for ten
years from C. F. Hodson, 1, Gough-square, Fleet-street,
E.C., for seven stamps; or by applying to the College
direct; but if he intends entering the profession, he
had better matriculate at the London University. On
applying at any of the London colleges he will get a
prospectus giving valuable hints as to study, especially
St. Bartholomew's Calendar.-A. H. N.

[5885.]-CISTERN.-Of course the pipe E, if as wide, will discharge more water than F higher up in the same time, in the ratio that the water above it + 15lb. per square inch is heavier than the water above F +15lb. per square inch. Water is 800 times heavier than air, though as steam it is but about 9-15ths the weight of air. -B.

inquired after by" G. F. O." is Carre's ice machine. The [5894.]-FREEZING APPARATUS.-The machine price complete, in England, of the smallest size is about £6, to make 1lb. of ice at time. Highly concentra‘ei [5553.]-SCHOLARSHIP.-W. C. Royalt had better liquid ammonia is used, not ether. The American in

MAKER.