The annexed sketch (Plate LXX. Fig. 2) will represent the means proposed for introducing a constant supply of gas by means of a double barrel condensing syringe, worked by a rack and sector; in which let A B represent two small condensing syringes, joined together at bottom with two plungers working in them, moved by the handle, D, and sector, C. There is also another tube, G, for the supply of gas from the bag, F, to the barrels. It will appear evident that by moving the handle the plungers will be ultimately raised and depressed, thus forcing a constant stream through the alternate valves, A A and B, to the reservoir, E. It will be advisable to place a small safety valve in the top of the reservoir, as represented at H, for the purpose of allowing a portion of the to escape, should it be supplied too fast by the syringes. The jet will be thus regularly maintained, and for any length of time. It might be conveniently attached to the treadle of a turning lathe, and thus filled by the foot, by substituting a crank for the sector. I remain, Sir, respectfully yours, R. W. BARCHARD. X. Another Improvement. By Mr. Booth. (To Dr. Thomson.) gas DEAR SIR, Barnet, April 15, 1817. Having noticed several improvements proposed, in order to render the use of the gaseous blow-pipe more safe, I have been induced to make a further alteration in the construction of that useful instrument, which, by possessing several advantages of make, as well as extreme cheapness and simplicity, you may consider worthy a place in your Annals. The apparatus consists of a large bladder to contain the mixed gases, mounted with a stop-cock, by means of which it may be filled from a transferring receiver without the least trouble. It is then placed between two boards, the uppermost of which moves in a frame, and contains the weights requisite for condensing the gases. The stop-cock screws into the top of one of Professor Cumming's syfety cylinders, to which is added a jet of capillary tubes (as proposed by Dr. Clarke). [See Plate LXX. Fig. 3]. The advantages of this plan of construction are the following:— 1. Extreme readiness of construction. 2. The advantage of increasing or diminishing the force of the jet by means of the weights. 3. Great safety: for, as the last portion of mixed gases is forced out with the same degree of force as the first (which is not the case in the condensing one), there is not that chance of an explosion from the retrograde motion of the flame (supposing it able to overcome the other precautions, which is not likely) as there is in others. And should such an accident happen, it would be attended with comparatively little danger. On this account the number of tubes in the fagot, and the diameter of the jet, may be increased with safety. I am, Sir, yours truly, THOMAS S. Booтn. P.S. Since writing the above (which I intended to have sent you last month), I have been informed that a similar mode of construction has been adopted by the Marquis Ripolti) if I am correct in the name). He uses two bladders; the one containing the hydrogen being furnished with a jet tube twice the size of that containing the oxygen, and the condension formed by means of an iron bar, as the plan of using the gases separately does not appear to possess so good an effect as when combined in the same vessel. You may still consider my plan of sufficient safety and utility to lay before your readers. In the fourth number of the Literary Gazette, p. 57 (Feb. 15, 1817), the following intelligence is given :— "M. Von Synghel, of Ghent, has employed nine years of intense study for the purpose of finding out some method of simplifying arithmetical calculations, and has succeeded, in the most complicated rules, in decomposing, producing, and reducing in one minute, and by means of a dozen figures, operations which required hours, and whole columns of almost unintelligible fractions. His method is applicable to money of all kinds." I dare say many of your readers, as well as myself, would be very glad to find this true. Will you, therefore, take the trouble to say if you know any thing respecting it; and if so, what means are to be taken to get possession of his method? Perhaps some of your correspondents may be acquainted with it, if you should not be. Will you also be so kind as to inform me what method is generally thought best to adopt for a person to teach himself mathematics, what books are preferred, and what order the different branches should be studied in? If you will indulge me with this information, I shall ever consider myself to be May 21, 1817. Your very obliged servant, B. P. I am sorry that it is not in my power to communicate any information respecting Von Synghel's alleged discovery, never having heard either of the discovery or its author till I received my correspondent's letter. The usual mode of studying mathematics in this country has been to read the first four books of Euclid; then to learn algebra, as far as the solution of quadratic equations; after this, the fifth, sixth, eleventh, and twelfth books of Euclid may be studied; trigonometry naturally follows; then conic sections; then fluctions. The best book on algebra that I have seen, as far as it goes, is Euler's, of which we have an English translation, I believe by Mr. Horner, of Bath; though I state this upon rather hearsay evidence. For the higher branches of mathematics, Euler's books are still the best; nor is it likely that they will soon be excelled : they possess a clearness not to be found in any other writer on the higher branches of mathematics that I have ever looked into.-T. XII. Singular Formation found within an Egg. By Mr. Strutt. (To Dr. Thomson.) SIR, Having accidentally met with a curious formation in the inside of a common hen's egg, I have taken the liberty of sending an account of it for insertion in your Annals of next month. This formation was discovered floating in the white part of a common egg. The outside consists of a shell exactly similar to that of the egg itself, but not so thick, and of a darker colour. It is about one inch and three quarters in length. Its greatest diameter, which is near the upper end, is about three quarters of an inch, and it tapers down to a point at the other end of an eighth of an inch in diameter. By piercing it at the top, and at the bottom, I was enabled, by applying my mouth to one end, to force out the contents, which I found exactly similar to the white of an egg, but there was no yolk. The shell gradually becomes thinner as it approaches the narrower end. In the centre of it, on the surface, there is an indentation, or ring, which extends a little more than half round the egg; and about a quarter of an inch from the narrower end there is another indentation, which extends almost the whole of the way round. The egg in which this singular curiosity was found was good in every other respect, and had in it a perfect yolk. Derby, May 21, 1817. I am, Sir, your obedient servant, J. D. STRUTT. XIII, Effect of different Rocks in Scotland on the Magnetic Needle. SIR, By Mr. Webster. (To Dr. Thomson.) Edinburgh, June 10, 1817. The curious fact some years since noticed by my friend Professor Jameson, and lately by Dr. Macculloch, that the magnetic needle was sensibly affected when in contact with the granite of certain districts, led me to pay particular attention to the circumstance in a late tour through the highlands of Scotland. The instrument I used was the common miner's compass, and a comparison was often made with another of the same size and construction, placed in a distant situation. Throughout the great formation of mica-slate between Tarbet and Tummel Bridge, the needle was often rendered stationary when the instrument was in contact with the strata. In other instances it varied from 3 to 8, and 15° from the point indicated by the other instrument, and it was more than once much agitated when brought near the subordinate beds of hornblende rock and felspar. In the gneiss district of Garviemore I remarked but two instances, in which the motions of the needle were unusual; but at the wellknown veins of granite at the Bridge of Grey it was rendered nearly useless, both when in contact with the veins, and when at some distance from them. At the Fall of Fyers, when endeavouring to ascertain the position of the sienitic granite and the conglomerate, the motions of the needle were so irregular and varying, that little or no dependance could be placed upon it. This was the case both with regard to the granite and conglomerate. I was somewhat surprised to observe no effect whatever upon the motion of the needle when presented to the granite of Portsoy, but a very decided and powerful effect from the serpentine, whenever the instrument was brought within a few feet of it. The granite of Aberdeen produced in some instances an effect, in others not the slightest, and this in different parts of the same vein. The only instance in which I have seen the action of the needle disturbed by the rocks of the trap formation was at Stonehaven, where an extensive bed and alternations of trap tuff with the other rocks occur. Here the needle was often, indeed almost constantly, affected. This may perhaps be in some degree attributed to the presence of red and brown hæmatite, which occur in innumerable small veins in the tuff. I have lately made some comparative experiments with the trap tuff of Salisbury Craig and Arthur's Seat, but have ever found the needle perfectly free in its motions. The green-stone of Salisbury Craig, however, frequently affects the needle, even in hand specimens; but in these the glass discovers numerous specks of the hydrate of iron, and often of the sulphuret, to the presence of which we must attribute this circumstance. In no instance have I found a piece of pure green-stone produce any effect. I expected to have found some of the sand-stones, especially the old red sand-stone, affect the instrument; but in no instance were my expectations realised. It may not be improper here to remark that I found sulphuret of iron in considerable quantity in the granite veins of Garviemore, and brown hæmatite in one instance at Aberdeen. I am, Sir, yours, &c. J. W. WEBSTER. XIV. Fusion of Wood Tin. Dr. Clarke, of Cambridge, has made a curious addition to our knowledge respecting wood tin. When exposed to the action of his powerful oxygen and hydrogen blow-pipe, it fuses completely, acquires a colour nearly similar to that of plumbago, with a very strong metallic lustre. Dr. Clarke was so obliging as to give me some specimens of wood tin thus fused. It was very hard; as far as I could judge, nearly as much so as common tin-stone. It was brittle, and easily reducible to a fine powder. I found it not in the least acted on by nitric acid, muriatic acid, and nitro-muriatic acid, even when assisted by heat. Hence it must still continue in the state of an oxide. The circumstance that wood tin (and probably tin-stone also) acquires a metallic lustre when fused, seems to decide a subject which has been agitated in this country with much keenness. It was asserted by Dr. Hutton, and is still maintained by his followers, that all granite has been in à state of igneous fusion. From Dr. Clarke's experiment, it may be inferred, with considerable confidence, that the granite in which the ores of tin occur has never been in a state of fusion. XV. Turkey Oil-stone. This stone, which comes from Iconium, in Asia Minor, and is used as a whet-stone, was lately analyzed by Mr. Holme, from a specimen given to Dr. Clarke by Mr. Knight, of Foster-lane. Its constituents were as follows :— XVI. Black Powder remaining after the Solution of Tin in Mu riatic Acid. Mr. Holme has lately analysed this black powder, which has been long known, and generally supposed to contain arsenic. He finds it a pure protoxide of copper. I think it but fair to mention that I had beeen informed by Dr. Wollaston, several months before I heard of Mr. Holme's experiments, that the black powder was copper. Dr. Wollaston had determined its nature by experiment. XVII. Holmite. Dr. Clarke has given this name to a singular lime-stone found in the pavement of Cambridge, and analysed by Mr. Holme. The following is his account of it : -- "It was found in the pavement of our streets, and brought to me as a mass of emery. Its effervescence in warm acids betrayed its real nature; but its remarkable specific gravity, which equals 3.597, being equal to, if not greater than Jameson's compact brown iron-stone (vol. iii. p. 258), induced me to pay more attention to it. When acted upon by the blow-pipe, minute particles exhibiting a pseudo-metallic lustre are manifested, and these of course are mica; but they are not visible until the stone has been thus heated. When this mineral was first brought to me it had the form of an oblique, rhomboidal, four-sided prism. It was of very considerable magnitude. We know not whence it came; therefore, |