VARIORUM. [1445] SUCH a letter as "Neutral's" (1396) ought not to have been anonymous. He should note how Mr. H. C. Key, in applying the same sort of criticism even to an anonymous writer, very properly gives his name. By writing as he has, "A Neutral" exposes "E. L. G." to grave suspicion; and he' strengthens the suspicion by adopting "E. L. G.'s" own most peculiar plan of making theories for others. I suppose I shall be bound to believe soon that a solid really can be squeezed into a gas; and so have to admit that this idea was not a jest of mine Can there be two who do not see that the idea was even more absurd to me than the other idea I commented on, that a solid can be squeezed into a liquid? or who suppose that while opposing "E. L. G." on this last point, I should be likely to assert a yet more extravagant view on my own ac count." As respects the question of courtesy, it happens fortunately that I had explained to you in private how my application of Montaigne's rule to "E. L. G." was merely an experiment. "E. L. G." had said a very rade thing about myself and " F.R.A. S.," and I determined to see how he would stand a mildly rude remark about himself,-whether he would take it handsomely or grow very angry, or (finally) sulk over it. I cordially endorse the remark that "E. L. G." is no charlatan, but a man of ability and of varied attainmentsas indeed I remarked to yourself, you may remember. Yet no man, let his abilities or attainments be what they may, has a right to address thousands on a certain subject, while he admits he has not read a single book on that branch of science to which the subject belongs. In this respect there is no parallelism between "E. L. G.'s" remarks on a meteorological subject and mine on the effects of pressure; for, in the first place, the latter subject was forced on me much against my will by "E. L. G.;" and, in the second, I do not boast of having read no book on the subject, but on the contrary have read and studied many. In any case, "A Neutral" (always setting aside the above-mentioned suspicion) should have weighed "E. L. G.'s" misdeeds against mine; and if he has a rebuke for my mild charge of blundering (though I made no such charge against "E. L. G." be it noted) he should have found another and a severer one for "E. L. G.'s" gross charge of scorning or ignoring evidence. Let me furthermore note that it was not with reference to E. L. G.'s" views about pressure that I quoted Montaigue, but on his writing about a meteorological subject, while asserting that he had read no work on meteorology. This was too bad, let "Neutral" say what he will. And now, lest any one else who may have read but one or two letters of this correspondence should fall into the mistake of pronouncing judgment without knowing (or choosing to ignore) the points really at issue, let me hasten to remark that I am perfectly well aware that in one sense ice may be squeezed into the liquid form. Its fusing point, or the fusing point of any substance which expands on solidifying, is lowered by pressure. But this lowering is a regular process, and for a definito pressure there is a definite fusing point. "E. L. G.'s" assertion was that independently of temperature a solid becomes fluid under pressure; and he extended this to all substances, even those whose fusing points rise under pressure. My challenge is not touched or even approached by "Neutral's" answer, for I referred specially to "E. L. G.'s" assertion that the fluidity resulting from pressure is independent of temperature. I see that "F.R.A.S." (who, like myself cannot, it seems, please all) is accused of not being scrupulous or moderate in his statements about astronomical com'pilations. Now I know nothing whatever of Mr. Darby's book, but I do know something of" Chambers's, Handbook,' 'Lockyer's Lessons," and other compilations in astronomy; and I cannot but agree with the general remark of "F.R.A.S." as to "paste and scissors books." That in one sense such books are of authority is doubtless true; books containing the results, opinions, and methods of our best astronomers must needs be so. It is true also that such books are sometimes of great use. But the fact is, as Emerson has stated it, that a man must show his power of producing original work of the same kind before he can claim a right to compile. If this is true in literature,it is a fortiori true in science. I care not how freely a man compiles, whether with acknowledgment, as in Mr. Chambers's case, or without, as (too often) in Mr. Lockyer's, so long as he is capable of forming an opinion for himself on the subjects he treats of; but, if not, he has no right to compile, and cannot fail to mislead his readers, because he is sure in some parts of his work) to misunderstand his authorities. In this matter I think "F.R.A.S." has done well to speak plainly. We must not let the convenience of certain works blind us to the fact that they ought never to have been published. I quite understood Mr. Birt's question; but he must be aware that it is one which cannot be answered without a considerable expenditure of time and research. I am far below Mr. Denning's standard-by no means able to write down off-hand the relations of any astronomical subject which may be proposed to me. In this case I should apply to Mr. Birt for information rather than he to me. The moon is understood to be his special subject; at his fingers' ends so to speak. I could only get what I want (as the basis of the mathematical inquiry he suggests) by looking up certain works not at my hand. Will he give me the following details ?— 1. The exact point in the northern heavens to which the moon's polar axis is directed at some stated epoch; *We beg to inform Mr. Procter that " E. L. G." and A Neutral" are two distinct correspondents.-ED. 2. The exact changes of place to which this point is subjected; and, 3, the rates of such changes. I do not say that I cannot find these things out for myself; ont I have not time to, at present; and they must be as the alphabet to Mr. Birt. unintentionally done to him. Judging of his views by I have to apologize to "J. K. P." for a wrong I have a letter in which "E. L. G." referred to them, I supposed he meant to describe a certain mode of obtaining the C. G. of an elliptic quadrantal surface as theoreproximate solution deduced by an exact method, and tically exact. I find it was given by him as an apthat method the most convenient of all for determining the C. G. of such a surface. It will be seen, therefore, that "J. K. P." was not, as I supposed, essentially wrong, but, on the contrary, strictly right in this matter. RICHARD A. PROCTOR. MATHEMATICS OF LIMITS. [1446] MR. HUDSON (let. 1438) has misunderstood idea of the infinite"--whether the infinitely great or me if he supposes I conceive that "a clear and positive the infinitely small-can be formed by any man, mathematician or non-mathematician. I cannot suppose he will be able to quote any mathematician who has entertained such a view. I assuredly agree with Mr. Hudson in affirming the contrary. What I have asserted is, that to the mathematician the completeness of a proof supplied by the method of limits is obvious, whereas, to the non-mathematical mind, a proof founded on the method of limits seems unsatisfactory. So far, I believe, Mr. Hudson will perfectly agree with me-I go no farther. RICHARD A. PROCTOR, A CORRECTION. illuminating a desk (in my third paper on the dif[1447] IN working out the problem about a lamp ferential calculus), I made a mistake, adding instead of subtracting 8° at one stage of the work. The proper height of the lamp comes out about 15in. instead of 18 in., when this correction is attended to. RICHARD A. PROCTOR. turbances is SUN SPOTS AND THE PLANETS. [1448] IT is news to me that the influence of the planets on the solar atmosphere is an established fact, and Loewy by no means express conviction on the as Mr. Holden asserts (let. 1481). De La Rue, Stewart, subject; nor do Sir John Herschel, Prof. Wolf, and Prof. Kirkwood, who have given more attention to the matter than most. The cause of solar atmospheric disvery far from being certainly known. Where, by the way, do Messrs. Lockyer and Balfour Stewart distinctly tell us that the spots on the sun are due to planetary influence?" And how comes Mr. Lockyer to be an authority on this special subject? He is an excellent observer, but it is well known that he is not difficult question depends; nor has he directed any of his versed in the dynamical and physical laws on which this observing energies to this special point. Dr. Stewart's opinion is altogether more germane to the matter; and I am convinced so skilful a physicist and so cautious a reasoner can have expressed no such rash opinion as Mr. Holden has mentioned. Dr. Stewart has said that so far as the evidence goes it is in favour of such a theory, but I am sure he has not distinctly told us the theory is the true one. If the theory were established-yet inasmuch as it pays attention to the mass, distance, latitude, and so on, of the several planets-it is by no means to be compared with Mr. Pratt's. RICHARD A. PROCTOR. [1449] In his article, No. 503, p. 68, Mark Ellor says, "this charge is tenable, but not fair," and alleges it is equally to be preferred against the pianoforte, in support of which allegation he claims the testimony of my friend "W. T." and myself. Now it is quite true both of us have long desired some better and more effective means of rendering the treble of pianofortes more powerful than the usual one, viz., increasing the number of strings to each note, for there are many great practical objections to doing this, and after all it hardly deserves to be termed efficient. I have carried out the multiplication of unisonous strings in the piano to a considerable extent, but the result is far from satisfactory to me. There are now before me two notes, F and F sharp (2in. long), the former has four and the latter two No. 16 wire strings. When struck by the same hammer there is much less difference in their loudness than might be expected; the increase of power by employing four strings certainly is not worth the great additional labour of tuning they render needful. In confirmation of this fact I may mention that within the last three years I have tried many of Collard's trichord (cottage) trebles. Now, Messrs. Collard's reputation is deservedly very high, and their trebles are usually good; so we may expect that if the addition of the third string was capable of much increasing their loudness, that fact would have been very patent, but in almost every instance their trebles are not so loud as the bichord trebles of Messrs. Holdernesse's pianos, with which I compared them; so my faith in many unisons underwent a severe shock. Nevertheless, I carried out my original intention to employ four strings in the treble of my grand-the result is stated above. Allow me to add I am not the first unwise person who has used four strings to one note. I saw the same folly-if it be one-in some cottage pianos made by Debain, more than twenty years ago; and a tuner with whom I am acquainted, informs me he operated on some other pianos with four strings, of French manufacture, in the seraglios at Constantinople. He added, "those pianos were terrible Turks" to tune. but that (even when only two strings are used to one note) they are usually as weak in proportion to their basses as the treble of an ordinary harmonium is in proportion to its bass, is not in accordance with my exsiderably in different pianos by the same makerperience. This defect is one of degree, and varies conprobably to a considerable extent from want of dae care in manufacture. The piano has the great advantage of expression by the finger touch. We can force the melody and subdue the accompaniment to our taste, an advantage which the harmonium-as ordinarily constructed-does not afford the performer, for in that instrument he has no means of keeping down the voices of the growlers-I mean the bass reeds. I am far from alleging that this defect is inseparable wind instrument with keys capable of greater expres from the harmonium; on the contrary, I know no sion than a good concertina (which is the harmonium's first cousin); and I see no reason why the harmonium might not he made equally capable of expression with it. No doubt a great deal may be, and is, done by "foot-touch" with the expression stop, and, be it remembered harmoniums have been constructed with expression à la main. To what extent this has been carried I am ignorant, having seen but one or two, which were not very satisfactory: but that does not condemn the principle, only its carrying ont. I can see no reason why it might not be applied ont so as to give the player as great a command over the varying loudness of this instrument's sounds as we obtain by foot-touch or by varying the pressure of wind in the concertina. It seems a mere question of "using the commercial than a scientific question whether the means; " and I cannot help thinking it is rather a means shall or shall not be used. The defect of weakness in piano trebles is notorious; Mark Ellor says this same defect exists in pipe organs. Quite true; but I think-unless his experience of harmonium trebles has been far more satisfactory than mine-he will admit that in the organ it exists in a much smaller degree. The voicer, at the cost of some deterioration of quality, can make treble organ pipes speak loud enough to cause the melody to be heard, even when accompanied with judgment by pipes of the same ranks. Of course a better effect is obtained by the melody is played. accompanying with a softer stop than that on which harmonium, if it has two ranks of keys, without which I consider it never ought to be constructed if intended for any higher musical effects than droning out accompaniments to psalm tunes. An harmonium with one rank of keys is quite unfit for proper performance of melody and accompaniment, unless the former be restricted to a compass above F-where the half ranks of reeds are divided-and the latter never allowed to rise above that note. Under these circummelody performed on a louder treble rank; but this is stances a soft bass rank may be used to accompany a like dancing in fetters-freedom of movement is quite out of the performer's power. We can do this also with the Reinforcement of the treble, as suggested by Mark Ellor (by the multiplication of unisons), is a very natural and obvious method; little other objection but that of increased cost can be made to it. In the harmonium, as in the organ and piano, we are limited to something like the ordinary proportions in the length and width of our scales; this would seem to be the only practical method of obtaining trebles of the loudness we require. Glad, indeed, should I be if Mark Ellor, or any other of my practical fellow-readers, would inform me if considerations of timbres, &c., do thus limit the width and length of harmonium reeds. For anything I am able to see to the contrary, it would appear that if a reed in. wide, with a suitable wind channel, produces a sound whose loudness we may for convenience call 1, and four such reeds produce sounds whose loudness is = 4, that a single reed of the same length, but 4-8in. wide, having a suitable wind channel, being connected with it, ought to produce a sound whose loudness is equal to that of the four unisonous reeds. The same quantity of air would escape from the aperture in. wide at each vibration of this wide reed as escapes from four apertures each of which is only in; or one-fourth its width at each of the vibrations of the narrow reeds; loudness being said (c. p.) to depend on the quantity of matter in motion. It might be supposed very wide reeds would resemble wise men, in being slow of speech; but this seems an error. I apprehend the slow or quick speaking of a reed (c. p.) depends on the proportions between its rigidity and the force employed to move it. If a reed be four times the width of another it will (c. p.), be four times as rigid, therefore it will require four times the force to put it into vibration within the same time; but this additional force must necessarily be communicated to it although the weight of wind be unaltered, because the wide reed exposes four times the surface to the wind's pressure. Therefore it would seem it ought to be moved and made to speak as quickly as the narrow reed. I need hardly add it will require more wind-just as employing four narrow reeds would do-but probably not more than them, if indeed quite so much: there would be less leakage in proportion to its beating surface. One wide reed would also cost less to make, voice, and tune than four; besides, when re-tuning becomes needful, there would be only one to do. While on the subject of the harmonium, let me add that in commor with Mark Ellor, and I suspect every other musical fellow-reader, I am longing for the # I push, and it took the curve indicated by the dotted lines. Showing clearly to my mind that the coning of the wheels does not in the slightest degree assist the vehicle to take the curve; and also showing that it is entirely governed by the radiation of the axles. The cones are not only of no use, but they are a decided disadvantage: for this reason, when running on a straight piece of line, the horizontal position of the axle is continually shifting, as shown by the dotted lines in Fig. 3. The cause of its doing so is apparent, it being the cone of the wheels first mounting on one rail and then on the other, causing the very unpleasant undulating motion frequently felt in the railway train. on the evening of the 21st of January last, I made the I believe under certain conditions the coning of tires sketch I enclose. On comparing it with Mr. Webb's map I see some important differences. The questio whether there are any changes taking place on the moon's surface has so much importance in the min of observers, that I feel sure Mr. Webb will exce if I trouble him with one or two questions concerning these clefts. It seems to me that the south-western cleft is longer than marked on Mr. Webb's map by portion from A to B, which goes through a very hilly country. The same remark is applicable to the eastern cleft from C to D. I observed also that the left cleft is prolonged beyond [the open ring of H palus for some distance towards the north from Be G. This portion is not shown on Mr. Webb's Would Mr. Webb kindly state whether the prolongatin of these clefts is shown in Beer and Maedler's map, and whether he has observed them himself ta prolonged? I failed to identify the fourth cleft, s to be north-east of A. Those who observed the lozenge west of Fontan during the evening hours of January 31st, did not f I believe, to see the cross of Beer and Maedler. I myself a good perspective view of this cariens o It seemed, at the time, to form the end of the interr ridge towards the north, and about the same dista west of the one I sketched last year, as this one is tr the crater of Fontenelle. Allow me before I close this to tender my thanks Mr. Webb for his kind promise of a sketch of Gass by Schmidt, with 14 clefts. Through the kindnesda gentleman I have been put in possession of fore these sketches, among which there is one fr Schmidt, but as it contains only 10 clefts it is not, dently, the same as the one mentioned by Mr. We Jumet-Hainaut, Belgium. FOREIGNER TOOTH OF AMPHISAURUS AMBLYODUS [1456] THERE are few departments of microsp that which has relation to structural odontology, an cal research more interesting and instructive than a perhaps in the entire range of microscopical investi neglected. Since the publication of Professor O tion there is not any department which has been m "Odontography," I am unacquainted with any bok in which odontological structures have been st matically illustrated, and yet the field is s once most beautiful, because of the elegance of the forms it contains; and most valuable, 20 gically and paleontologically, in enabling compart tive anatomists to determine the generic and specie difference in teeth which externally bear very consider able resemblance to each other, and are therefore by merely external examination difficult to interpret There have, within the last few years, been discorrad in the Northumberland coal shales a considere number of reptiles of various sizes, and not only a the specimens found numerous, but the generic and specific differences of the reptiles are extensive also. Three reptiles of small size have been discovered and four genera of large reptiles-viz., Pteropi cornuta, Macrosaurus polyspondylus, Orthosaurus pa cephalus, and Amphisaurus amblyodus. Of Pteroplar, headbones, jaws, teeth, and vertebræ have bees found; of Macrosaurus, eighty consecutive verte bræ, having a total length of 56in., together with ribs and limb bones have been discovered; of Ortho rus, an entire cranium, 15 in. long and Shin. broad, as been obtained; and of Amphisaurus amblyodus, portions of jaws containing teeth are now in my possession. It direct the special attention of your paleontological is to the teeth of the latter reptiles I desire to readers. I am indebted to Mr. John Sim, of West Cramlington, for the very excellent section of the tooth which furnished the illustration annexed; and to that gentleman and Mr. Joseph Taylor I am deeply indebted of sections of remains of coal-measure fishes and for valuable aid in making an almost complete series reptiles. Figure 1 represents a section of the tooth about ths. of an inch from the base, natural size. Fig. 3, the same section magnified three diameters. Fig. 8, further magnified. teeth there are, so far as I am aware, no teeth resembl In the whole range of published figures of sections of bling those of Amphisaurus. The tooth of Anthracosaurs scribed by Professor Huxley in the Quarterly Journal the Geological Society, Vol. XIX., p. 61, to a slight ent resembles it, but the differences are so manifest, o far as they can be determined from the description ithout an illustration, as to render a discrimination etween the two a matter of the utmost ease. [1457] YOUR correspondent (let. 1365, p. 493) gives me information respecting the species of crocus from hich saffron was derived, and when it was cultivated this country, which does not agree with British otanical works. The crocus which was cultivated in Ingland is, in Sowerby's "English Botany," vol. IX., late M,CCCC,XCVIII., figured and described as a ellow-flowered species (C. aureus), flowering with its eaves in spring; indeed, it very closely resembles the ommon yellow crocus of our gardens. Crocus sativus is one of those species which produce heir purplish flowers in the autumn without the leaves. affron is not now in repute, except for making an nfusion to cause measles to come out more freely, and s a restorative for cage birds when moulting. Its dour is said to have a powerful effect on those who SOFT SOLDER, GILDING, ELECTRICAL, ETC. [1460] (6414.) SOFT SOLDERING IRON AND STEEL.If "Geo. G." will saturate his chloride of zinc with finely pounded sal ammoniac, hewill find it a far better flux for soft soldering iron or steel than the simple chloride of zine; but why he should allow either to remain so long on his work after he has performed the operation for which it was applied, I cannot conceive, since, if at once removed, no rusting will take place-at least, such is my experience-and I should most certainly blame the operator rather than the chloride in the event of any rust appearing. (6427.) Gilding. The cell referred to is large enough for gilding small articles, but the process for making should be spoiled (by the incompetence of the amateur), the depositing bath is so complex, and if the materials mend "A Dentist" to purchase the bath ready-made, so costly in its nature, that I should strongly recomin the same manner as he has done with regard to the cell, only apply to the operative chemist to make it up. The fluid itself, as generally used, is the double cyanide of gold and ammonium in solution, with a plate of gold, offering at least equal surface to the articles to be plated, attached to the silver element of the battery, the articles being attached by suitable wires to the zine elements. The solution should be worked at a temperature of from 140° to 200°, the latter being pre (6428.) Area of Cylinder.-I think "Alfred" has misunderstood Mr. Baskerville, since the "area of a cylinder," as understood by engineers, is the superfices of the piston exposed to the steam force; hence, if the diameter of the cylinder is 15", the area would be 152 x 7854-176-715 square inches, which Mr. B. might, with very good grace, in explaining a principle, call 177 square inches; but so far as the "area of the cylinder" is concerned, in the light it was spoken of by Mr. B., it has nothing whatever to do with the "Alfred" himself, not by Mr. Baskerville. length of stroke-an element here misplaced by (6437.) Wyld's Magneto-electric Machine.-I regret very much that I cannot assist "Tutor" in his difficulty, from the simple fact that I have not been able to get a glance at one of Wyld's machines, and much as I respect Dr. Ferguson for the truly valuable treatise he has given to the world upon "Electricity" as a science, I must say that I look upon his "Appendix," presumed to describe this wondrous mack ine, as an utter failure, so far as conveying any intelligible description of its parts, the function each part has to perform, and the means by which the grand result is ultimately to be In so far as I have been able to grasp the subject from the description given of the parts of the machine, can only look upon it as a plain magneto-electric machine by which, taking advantage of the best form of armature (by no means Wyld's invention), he has succeeded in converting the greatest amount of mechan cal into electrical force, ultimately developing this into a concentrated heat force, forming a nearer approximate approach to the heat originally expended than has been obtained by any other machine yet contrived. This, however, is so far hypothetical, as I am not aware that the machine has yet been tested comparatively in every respect with those of Professor Holmes and others who have sought for the conversion of force in similar directions, a matter which the Royal Society, or some such body, alone have the means of taking in hand to determine. I hope I shall not be misunderstood here as desiring to detract from the value of Mr. Wyld's invention, because some of the principles involved were known before he came into the field: far, very far from it; as an individual, I only too keenly appreciate and humbly applaud the genius of the gentleman who, taking scattered facts in hand, so combined them as to give the world a result so far as we know of not yet excelled, even if equalled. All I wish to see is that it should be placed on its true pedestal in the historical collection of scientific inventions. With regard to the laws of electro-magnetism, Dr. Ferguson, as quoted by "Tutor" is quite correct, but the cases he assumes are not parallel. "The long coil of thin wire" does daily, hourly, induce magnetism in the core, say, of a relay-magnet, with only the ghost of a current in circuit, but then the "magnetic force" (attraction) necessary to be induced, is only of such an amount as to attract the armature of a well-poised lever, so nicely hung that almost a breath of air would do the same duty. And it does this because the induced force is due to the current passing, multiplied by the number of convolutions surrounding the core, which in the case of the long thin wire is very great; but if he passes the same current through a few convolutions of thick wire, the magnetic effects are proportionally reduced. Say for instance we have an electro-magnet with 5,000 convolations of wire well insulated, and another with only 50 in the same condition, if we put I intensity of current, then we can never make 5,000 I 50 I, but we can understand that in accordance with the laws of electro-magnetism, the force developed in the one case, as compared with that in the other, would be, cateris paribus, 100 times greater. 5000 I 50 I = = = The only other point upon which I can now touch in "Tutor's" note, is that the magneto-electric current is always an induced one, and as such approaches in nature, if it be not in reality, a static charge. Such being the case, its tension is indefinitely higher than the difference of tensions which produce the electro-motive force in dynamical electricity; hence the resistance offered by any metallic wire, however long and thin, is almost nil, when compared with the resistance to the flow of a current produced by a battery, even through a short length of similar wire. This will become evident to "Tutor" if he studies the philosophy of the induction coil, where we find that the induced current from the terminals of the secondary will give an arc of flame (a continuous current with the excessively bad conductor air) say 23in. long, while if the terminals of the primary of the same coil are separated only 1-16 of an inch, with the same source in action, it is very problematical if any current at all would pass. (Not proven.) (6452.) Night Lights.-The wicks, and, no doubt, a license to make the night lights, can be obtained from Price's Patent Candle Company (Limited). The lights are not burned in water, but the boxes which contain them are generally floated on water by careful housewives, to prevent an accident from any spirting of defective wicks, or the possible result of firing the box by the last dying glimmer. (6456.) Electrical. The zincs should be at least the same size as the silver plate, and for economy, the back part coated with sealing-wax varnish; this will save your zinc and deteriorate very little from the intensity of your current, but let the sides facing your silver be well amalgamated. In reply to your other query, you can cut your zincs and silver into 2 or 20 pieces, always supposing that you cause the same surface to be immersed in the liquid, and further, that all the zincs are joined up together, and all the silvers coupled in like manner, and you will get the same result, only for one thing, by doing so you increase your external resistance by the amount of wire or other means you use to join up the dismembered parts, and by so doing you reduce the intensity of current not directly in proportion to this new resistance, but in proportion to the effect it has on the equation I = sumed E = where the new resistance may be asZ, then the equation would become If you have such a cell, leave well enough alone. We cannot make a perfect one yet, but any one can spoil the best yet made. I = E that refers to the last sentence "Have a holder-up if (6519.) Communicators.-" Eggelre Reeb" means a ornaments there may be in the room where they permitted to dwell. May I hint en passant that abo nine or ten years ago I tested and described a form of Grove's cell in which, although kept on short ciremit some 24 hours, strips of litmus paper laid over the mouth of the cell did not become red! It would be a interesting subject of calculation to financiers w deal in small fractions of gain were they to investigate the results obtainable by the introduction of even the little improvement on all our telegraphic lines; but u the inventor shrank from pushing his invention even fore the then existing telegraphic companies, h much more so would he now fall back, rather than tempt to enforce his claims when all the hnes are the hands of Government. Reckoning back t Fontleroy,we might, were all the statistics before a show that hemp has removed from our country way very many, great bad men, but, if we had only an eq opportunity of appealing to statistics, I cannot e think that a far greater number of great good men Law been strangled by the apparently less tenacions ma W. TONKIA rial, red tape. HOT WATER APPARATUS (LET, 1584). [1461] ONE can scarcely think that a person fitting up an apparatus such as "Sub." describes, and vis the ENGLISH MECHANIC before him, would be at a d to know where the principle is wrong. The few pac should in all cases be taken from the highest pot the boiler, and gradually rise throughout the ve length of pipe over the surface intended to be he but not so with the return pipe, as that may either b or run level until it reaches the boiler, and should the be connected as near the bottom as possible, and account is a double or larger return pipe necesara But on looking at the sketch the case is the revers and it only being a shallow boiler with double res pipe, every opportunity is afforded for the we travel contrary to what "Sub" appears to han pected. The water on becoming heated travel ba the boiler to the highest point of the apparatus, A, but will not retain the same heat to B, have parted with it before arriving at that point, no doubt be nearly cold again, consequently and lating at all. But let him do away with the reters from one side and connect the pipe from A to b of boiler, and the flow pipe from top of boiler te ts bend above the floor, and the result will prove there will be perfect circulation throughout the F apparatus. The fact of the water circulating a does goes to show that the connections to the bar sy not in conformity with the way the pipes are s above the floor. There should also be an air up pipe fixed at A in order to allow the air to escape may be shut in on the pipes being charged As not shown where the branches are taken off, or position they are carried, I cannot say anything ab them, but am certain more heat would be ob than under the present arrangement. At the sam I do not consider it the best principle to fit ap paratus of this description, especially if it were 4in. pipes, but adopting my suggestion may As "Sab." has acted whole being taken down. query for himself and other readers, I hope he kat give them the benefit of his experience. (6476.) Medical Coils.-In the medical coils re- so that it cannot be too far withdrawn. The divisions and the return to the bottom; if he is not 1812 to air-pipe he had better do so; it helps c Branches for drawing hot water must be fixed flow-pipe. SAMUEL LAWS. P.S.-Should like to hear the result. STARCHES, ETC. [1468] KINDLY allow me to thank “J. C 1881) for his very courteous communication. The not much difference of opinion between us density or consistency of the starch granule F mange, as I know it, is a stiff gelatina pound, and living starch granules appear the average, of about the same consistency. appears to have formed his views from the dried starch-perhaps commercial starch. Sch readily be pounded into the dry dust, but en were the minute particles examined, I think would find that the fracture was that of a substance, and partook more of the character of us than crushing. "J. C." is correct beyond doubt supposition that starch granules, when mature, of several layers superimposed on the primata I have had the nucleus (hilum). Whether these have a COMEN vesting membrane is not, to my mind, a settled and it was to this that I referred when I defined granules in the letter to which "J. C." relas definition was a particularly unfortunate one, sita borrowed from the letter of an able scienti spondent who had written me the day previous me upon my then proposed attempt to starch. "You may as well attempt to eat a si a grape "(no difficult matter by the war, bei hardly know in what words to give a popular de of a "starch granule" that should bear a ma scientific scrutiny. Shall I define it as a " nuclens having superincumbent layers of gla substance of different densities, the whole hari appearance of a small bladder with strie?" would be more accurate but less unders "J. C." says that he considers these lavers "the form of investing bags." I don't think this (6478.) Poisonous Gas from Daniell's Battery.-I can only give the results of my own somewhat extensive experience with the Daniell, and that points to the utter absence of any poisonous exhalation from the battery. In fact I cannot conceive where such a gas could be derived from; so far as my limited knowledge extends, the only gas that could be evolved in the worst constructed battery would be pure hydrogen, and I apprehend that must be given off to an enormous extent and in a very limited atmosphere before it could assume the title of "poisonous." pleasure of visiting the cellars in which these cells are kept in constant action by some of the greatest of our As you are aware, sir, from a private letter I sent to metropolitan telegraph companies-some of which may you, I have been suddenly called away to perform a be aptly compared to a large necropolis with the coffinvery melancholy duty, and since my return I have not like batteries enclosed in boxes placed tier npon tierhad the pleasure of reading No. 807 until after writing and although there must have been hundreds of cells the preceding replies to such queries as I could conin constant action, I never felt even a sensation of veniently answer, taken as they came in No. 306. nansea on any visit I have made, still less any apI am now somewhat astonished to find that in reply-proach to a feeling of having been innocently poisoned. ing to the preceding correspondent I have also answered I think your correspondent "Telegraphist" must the question directly asked of me by T. A." in letter have mistaken the Daniell for the Bunsen or Grove's 1366, p. 494. For the Z there indicated is in fact the battery, in which case I would not answer for the rheostat or resistance coil hinted at by T. A.," and it purity of the atmosphere in a confined room with a there occupies its true position in the equation. large number of cells in constant action, since "nitrous (6350.(-Cracked Tube of Locomotive. W. L." has acid fumes" are not very friendly towards the human succeeded in giving perhaps the best known "botch" langs, nor the best means of oxygenating the chyle for a too frequent infirmity amongst our iron steds. I and venous blood, although they will generously perhave only one comment to make upon his letter, and form that operation on any bright metallic article or W .C.'s" attention to them. rises it becomes relatively lighter owing to the expan- GET AND GIVE. process is analogous to the ordinary deposit of, say, H. P. H. ........ 51° 51′ 14" 800 26° 27' Angle of 1-14th of circle W. M. F. P. CONCERNING BALLOONS (LET. 1818). [1465] I HAVE not yet had the pleasure of reading fr. Glaisher's "Voyages in the Air," but I have several aid to have ascended above seven miles, but I have been unable to discover any proof that he reached Deyond six. It appears to me very unlikely that, the eight of six being sufficient to produce insensibility, hat of seven should not be fatal. Even in one and he same narrative penned by Mr. Glaisher I find six and seven miles given as the greatest altitudes eached on the 5th of September, 1862. Mr. Roberts believes that the ascent was in July-it was on the date bove stated. The decrement of temperature found by Mr. Glaisher's experiments is not according to the law once advanced, namely 1° in 300ft. The decrement is remarkably irregular, as will be seen by the following table:Height. accounts of his remarkable ascent. Mr. Glaisher is 0 5,000 10,000 15,000 19,500 20,000 25,000 80,000 Temp. 62.2 41.4 31.0 21.0 10.6 0.0 5.3 (not 53°) On 18th August, at 25,000ft. the temperature of 23-9 was recorded, although the air at starting was at 696. Mr. Roberts asks if the balloon weighed more or less when the barometer fell to 10in. Why should there be any difference, except the extremely minute one caused by increased distance from the earth's centre? Its absolute weight was practically the same. Its relative weight depended upon that of the volume of gas in the balloon compared with an equal volume of the air, and its rising was due to this and to the ballast thrown out. I should think the change of temperature would affect both the gas and the air. The balloon could not have risen double as fast, on account of the rarity of the air. It is as reasonable to suppose that a cork would rise from the floor to the ceiling twice as fast as it would from the bottom of a pail of water. The balloon would not weigh threefold-on the contrary, less, on account of loss of ballast; and as it does not start filled, as it jority of our readers, especially those who have been MANAGER. THE VITRIOL CHAMBER AND GROVE'S CELL. Prepare a small Grove's cell, the porous pot being W. NETTLETON. RESISTANCE COILS. all current ceases. This current can only be a very small fraction of the total current. Now when we get a high total resistance in the direct paths, the total current itself becomes very small, and the difference between its two halves is so small as to be appreciable only by very perfect instruments, rarely possessed by those for whom I write. In fact, in my own case, possessing, as I do, instruments of my own make of considerable delicacy, I cannot by direct measure tell within two or three tenths of a unit when resistances of 100 and more are measuring, though with only 5 or 6 I can to less than a two-thousandth. The alternative is to work by average; get a definite observed measure on each side of the truth, and take the mean, and this applies equally in constructing the resistance and using it afterwards. Take an illustration: a 100 unit coil of 29 wire is about 100ft., and I cannot be quite sure to an inch of the exact length, that being an error of 1-10 unit nearly. I mark the spot at which the galvanometer turns 5 to the right, and then alter the length till it deflects as much the other way, and take the middle point. Some day I hope to have the opportunity of comparing my instrument with some of the costly ones, presumed to be accurate, and for the purpose have made loose coils of each denomination; but it must be remembered that an instrument of the same capacity as mine would cost probably 15 or 20 guineas, while the cost to me has been little over a pound in money; but I must admit a great deal of time was spent over it. There are also several ways of testing the results; for instance, by calculations according to Ohm's laws, but it would not be very easy. It must be remembered also that there is no "turn of the balance;" errors are as likely to be one way as the other, and therefore ten similar coils are very likely to approach closely to truth; the real difficulty is, as I have said, in making one exactly equal to that of the ten. Mr. Smith will see that I had anticipated his remarks on formulæ. Clark's book, to which he refers, was really written as an accompaniment to his galvanometer; hence the defect referred to. But it is a collection of desultory memoranda. I do not intend to go very valuable book in many respects, though rather a into the tension process by Thompson's electrometer, because it is not likely to be possessed by many readers, and as I have not one myself, I should have to copy from others-a thing I carefully avoid as much as possible. Other points referred to I have recently remarked on-such as size of battery-plates-or shall very soon be treating of. SIGMA. IRON AS A NEGATIVE POLE IN GALVANIC BATTERIES. [1469] Is your number for Jan. 20th, p. 425, Mr. James Howard mentions that some years ago I advo cated the use of iron as a negative pole in galvanie batteries. It is a fact that, with sulphuric acid as an exciting solution, iron is a more effective element than copper; not that iron is more highly negative than copper, for, on the contrary, iron is electro-positive to it. But the simple cause of the greater efficiency of iron is that it retains a clean surface while in action; consequently it offers less resistance to the circulation of the electric current. A copper negative plate soon gets foul-probably earthy bases and other bad conductors are precipitated upon it-whereas, the surface of an iron negative plate slightly dissolves away, and a clean face is constantly presented for the reception of the electric current. In the June or July, 1840 or 1841, number of the London and Edinburgh Philosophical It is, I think, entitled, "On an Anomalous Condition Magazine will be found a paper of mine on this subject. of Iron," and is an answer to a paper of Professor Poggendorf's, which purports to give an explanation of my discovery. I have at this moment no ready access to the back numbers, otherwise I would send; but the paper will be found at about the date mentioned. I also venture to refer to another paper of mine in the same publication for July, 1841, and in a subsequent number, entitled "On the Analogy between the Phenomena of the Electric and Nervous Influences." I think the experiments and theories there set out will interest some of your readers, especially as late anatomical investigations have much strengthened my theory. MARTYN ROBERTS. PLANING, MOULDING, AND GROOVING.- [1470] I AM much obliged to you for your kind offer to assist me privately. I enclose my address, which I will thank the Editor to forward to you. I think, however, that planing, moulding, and grooving in an "Amateur's" 5in. lathe deserves full elucidation in the pages of the MECHANIC. The instructions in the 2nd Vol. of Holtzapffel are confined to the saw. My own idea is to adapt to the saddle, and rising several inches above it, a cross slide, to which may be clamped "J. K. P.'s" apparatus for grooving taps (see Vol. X, page 281). A bed plate of proper strength and length, raised at each end, must be clamped to the lathe bed, leaving sufficient room for the saddle to traverse uncircular cutters. On this plan my difficulty is, first, derneath. The bed might then be placed true by the how in the best and simplest manner to clamp the wood to be operated on so as not to interfere with the cutters; and secondly, how to provide for operating on the thin edges of boards; thirdly, what is the best plan of rise and face for the cross slide to be clamped to the saddle; and lastly, whether any better scheme than A COUNTRY AMATEUR. the above can be devised. REMARKABLE RAINBOWS. [1471] IT is not at all necessary from the theory of the rainbow that when we travel towards one, like Mr. Birt (let. 1425), it should seem to recede. If it be caused by a rather dense wall, or screen of rain, whose boundary towards the spectator is straight, and crosses at right angles the direction of his shadow, his going towards it will rather make it apparently (contract in all its dimensions than recede; and if he approaches one foot or leg of it, the other must close up thereto, by a flank movement. Now, if the rain screen crosses his path at right angles, it will cross his shadow obliquely and further off, and his line of sight to the rainbow's other foot still further off. If he be on a vehicle, not obliged to look exactly ahead, and watches the latter foot of the bow, which may be the only part visible, it must plainly, in that case, advance to meet him, and may become apparently 30 yards nearer for every 10 yards he approaches it. As Mr. Birt did not observe his shadow to point otherwise than towards the second bow's centre, I see no reason to doubt it did so point. As every rainbow is a hollow cone, if we are anywise led to refer its different parts to unequal distances, it may give us the idea of being elliptical, or of any conic section whatever; the image of the retina alone must be circular. E. L. G. A MAIL OR TREASURE SAFE FOR SHIPS.] [1473] MAY I request the insertion of the accompanying paragraph on a new "treasure safe for ships," in the ENGLISH MECHANIC. The "Wreck Returns" of the British Isles show |