CHEMICAL NEWS, Gazzetta Chimica Italiana. Anno viii., 1878. Fasc. x. Certain Derivatives of Campho-thymol.-E. Paterno and F. Canzoneri.-An account of nitroso-campho-thymol and amdico-campho-thymol. Constitution of the Cymen of Cuminic Alcohol and of its Thymols.-E. Paterno and P. Spica.-Not suitable for abstraction. Propyl-benzoic Acid.-E. Paterno.-A claim of priority as against H. Koerner. Benzylated Cymen.-Dr. Girolamo Mazzara.-The author finds this compound to consist of-Carbon, 91.00; hydrogen, 9'10; and gives it the formula C6H3CH3C3H7C6H5CH2. Detection of Arsenic.-The matter containing the arsenious or arsenic acid is introduced into a Marsh's apparatus, and mixed with a concentrated solution of hydrogen is disengaged on applying heat. Antimoniucaustic potassa and a little aluminium foil. Arseniuretted retted hydrogen is not formed.-Moniteur Scientifique. Society of Arts, having received an application from the Technological Examinations.-The Council of the City and Guilds of London Institute for the Advancement of Technical Education, offering to take charge of the Technological Examinations established by this Society in 1873, and carried on up to the present time, have resolved to transfer these examinations to the charge of the Institute. The Council have also ascertained that the Science and Art Department will assist the City Institute in conducting the examinations, in the same way as it has hitherto assisted the Society of Arts. The Technological Examinations for the present year will, therefore, be carried on under the direction of the Institute, and all communicatious on the subject should be addressed to the Hon. Secretaries, City and Guilds of London Institute, Mercers' Hall. E.C. Process for Discovering the Effective Quantity of Tartaric Acid Contained in Dregs of Wine.-Prof. Francesco Dotto-Scribani.-This process serves for determining the effective quantity of tartaric acid not merely in unadulterated but even in the dregs of plastered wines. 10 grms. of the dregs are reduced to a very fine powder and dried in the water-bath, and then moistened and made into a paste with pure hydrochloric acid in a porcelain capsule, and allowed to stand for twenty-four hours. The mass is then lixiviated with boiling distilled water, the liquid is filtered, and this treatment is repeated with the residue upon the filter till the liquid passing through no longer reddens litmus paper. The filtrate is then boiled in a porcelain capsule, and whilst it is continually stirred with a glass spoon milk of lime obtained by levigation and passed through a strainer is added little by little until the liquid begins to turn red litmus paper blue. The capsule is then allowed to cool and the contents thrown upon a double filter, which has been previously well washed, and the precipitate is then washed, until on acidulating the washings with nitric acid and testing with nitrate of silver no turbidity is observed. The precipitate with the double filter is then dried in the water-bath and weighed, having care first to detach the outer from the inner filter, and to place the former in the weight-scale, and from its weight is deduced the effective quantity of tartaric acid, since 100 parts of calcium tartrate contain 57.69 parts of tartaric acid. This process is founded on the following principles:-The acid tartrate of potassium and the tartrate of calcium are less soluble in boiling water than in such water acidulated with hydrochloric acid, with which the two salts produce chlorides of potassium and calcium, while tartaric acid is set free. The colouring matter of the dregs is insoluble in hydro- MONDAY, 12th.-Royal Geographical, 8.30. chloric acid. Milk of lime has no action upon the chlorides, but transforms the tartaric acid into calcium tartrate. Science-Teaching in Public Schools.-A correspondent suggests that a careful and trustworthy account of the teaching of science in schools would be of great value, by laying before the public facts and not mere theories. As an instance of such theories he mentions the assumption of no less eminent a man than Sir J. Lubbock that boys would be anxious or willing to study science in play hours. He points out from among 500 boys few care to hear even such a lecturer as Prof. Tyndall, and none would go a second time except other work was remitted in compensation. Our friend informs us that at Harrow and at some other public schools any boy at the desire of his parents can give several hours weekly to practical work in chemistry or physics. "The parents of boys in general do not care about their learning practically, and it is from them, rather than from the masters, that the difficulty arises." May we suggest that such indifference or disinclination on the part of parents springs from the fact that successful practical work in science counts for little in determining a boy's standing in the schools? MISCELLANEOUS. In MEETINGS FOR THE WEEK. Society of Arts, 8. Recent Advances in Tele WEDNESDAY, 14th.-Society of Arts, 8. Chemistry in Australia.-Mr. R. W. E. MacIvor THURSDAY, A.I.C., &c., late Senior Assistant to Professor Dittmar, at Anderson's College, Glasgow, has for the last three years been engaged in lecturing to the farmers throughout Victoria on Agricultural Chemistry, and has succeeded in impressing upon them the importance of the subject, for many come 40 and even 50 miles to listen to him. referring to Mr. MacIvor's discourses, the Lancefield Chronicle for March 20 says:-" The amount of good derived from these scientific dissertations has been incalculable to the agriculturist, and the knowledge imparted has increased the prosperity of the country.' It is but fair to mention that these lectures are given free of charge to the agricultural community, the expense attending their delivery being borne by the Hon. William J. Clarke, M.L.C., President of the forthcoming Melbourne International Exhibition. Brake," Mr. E. D. Microscopical, 8. 15th.-Royal, 8.30. "The Automatic Hydraulic Barker. Royal Institution, 3. "Dissociation," by Prof. Royal Society Club, 6.30. Society of Arts, 8. "The History of Alizarin and Allied Colouring Matters, and their Production from Coal-Tar," by W. H. Perkin, F.R.S. Chemical, 8. "On Nitrification, Part II.," Robert Warington. "On Alkaloids of the Veratrums, Part III.," Dr. Wright and Mr. Luff. "On Alkaloids of the Veratrums, Part IV.," Dr. Wright. "On Alkaloids of the Aconites, Part IV., and on Japanese Aconite Roots," Dr. Wright and Mr. Luff. "Action of Hydrochloric Acid on Manganese Dioxide," S. Pickering. "Composition of Milk in Health and Disease," A. W. Blyth "Notes on the Effect of Alcohol on the Chemistry of Indigestion," W. H. Watson. 16th.-Royal Institution, 9. FRIDAY, cité," Prof. Cornu. "Etude Optique de l'Easti 17th.-Royal Institution, 3. "Architecture,” by Mr. H, H. Statham. Just published, with Illustrations, fcap. 8vo, cloth, 48. A MANUAL OF ORGANIC CHEMISTRY, Practical and Theoretical, for Colleges and Schools, Medical and Civil Service Examinations, and for Elementary, Advanced, and Honours Students at the Classes of the Science and Art Department, South Kensington. By HUGH CLEMENTS. London: BLACKIE and SON, 49 and 50, Old Bailey; Now Ready, crown 8vo., 600 pp., with 470 Wood Engravings, THE STUDENT'S TEXT BOOK OF ELECTRICITY. BY HENRY M. NOAD, Ph.D., F.R.S., author of "A Manual of Electricity," &c. A new edition, carefullly revised, with an introduction and additional chapters by W. H. PREECE, M.I.C.E., Vice-President of the Society of Telegraph Engineers, &c. Extract from Introduction by W. H. Preece, Esq. "The original plan of this book has been carefully adhered to so as to make it a reflex of the existing state of Electrical Science adapted for Students. Discovery seems to have progressed with marvellous strides; nevertheless it has now apparently ceased, and practical applications have commenced their career; and it is to give a faithful account of these that this fresh edition of Dr. Noad's valuable Text-Book is launched forth." London: CROSBY LOCKWOOD & Co., 7, Stationers', Hall Court. JUST PUBLISHED, 4th EDITION. GAS PURIFICATION & CHEMICAL CO., LIMITED, PATENTEES' MANUAL. 161, 162 163, PALMERSTON BUILDINGS, LONDON, E.C Of the Middle Temple, Barrister-at-Law, and Solicitor and Patent Agent, Assoc. Inst. C.E. 47, Lincoln's This Edition, much enlarged, gives a practical reference to every reported case of importance, and contains all the information on the law and practice of Patents Inventors and Patentees can require. The Appendix contains the Statutes and Rules, and a summary of the Laws of all Foreign States and British Colonies. London: LONGMANS and CO. IMPORTANT TO SULPHURIC ACID MANUFACTURERS. NORRINGTON'S PATENT. In the ordinary method of Manufacture, at the time of charging the Kilns, a considerable escape of gases takes place. This is attended with proportionate loss of Sulphur, and with much inconvenience to the workmen, as well as annoyance to the vicinity of the Works. This may be entirely avoided by the adoption of C. Norrington's patented invention, which can be applied at moderate cost to existing Plant, as well as in the erection of new Works. It may be seen in full operation on extensive Plant at Messrs. C. Norrington and Co.'s Chemical and Manure Works, Cattedown, Plymouth, where the fullest information may be obtained, with terms for license. NEW LIST of Collections of Minerals, Fossils, and Rocks, with prices. New List of Minerals for Chemical Purposes, Manufactures, and Research. New List of Varieties of Rocks. New List of Prices and Sizes of Cabinets for Natural History and other purposes. New Catalogue of Secondhand and New Books on Geology and Kindred Sciences. New Supplementary List of Books. New List of Sections of Rocks and Minerals for the Microscope. New List of Prices and Patterns for Geological Hammers. New List of Blowpipe Cabinets, Apparatus, and Materials. Also Implements and Appliances for practical work in Geology and Mineralogy. Post free on application to JAMES R. GREGORY, Geologists and Mineralogists' Repository, 88, Charlotte Street, Fitzroy Square London. PATENTS. Mr. Vaughan, F.C.S., British, Foreign, and Colonial PATENT AGENT. Special attention given to Inventions relating to Chemistry, Mining, and Metallurgy Guide to Inventors" Free by Post.-Offices, 67, Chancery Lane London, W.C., and 8, Houndgate Darlington. DARTON'S GIMEN POCKET DIRECT-VISION SPECTROSCOPE IN CASE COMPLETE, 21/-. DARTON'S CHEMICAL SPECTROSCOPE in POLISHED CASE 63s. Retort Stands, Bunsen's Burners, Gas Furnaces, and Chemica Apparatus of all kinds Made and Repaired for the Trade. F. DARTON & CO., 45, ST. JOHN STREET, WEST SMITHFIELD, E.C. (ESTABLISHED 1834), Makers to the Science and Art Department, DAVIS'S NITROMETER, 15/. IMPORTERS AND DEALERS IN CHEMICAL & PHYSICAL APPARATUS, 7, Exchange Street and 10, Half Moon Street, MANCHESTER. Illustrated Priced Catalogues Six Penny Stamps. Orders over 403 accompanied by a remittance are delivered Carriage paid at any Railway Station in England. NEWTON, KEATES, & CO., Sutton Oak Manure Works, ST HELENS: LANCASHIRE, MANUFACTURErs of PHOSPHATE OF SODA. Methylated Spirits.-David Smith Kidd, Licensed Maker, Commercial Street, Shoreditch, N.E Also FINISH, FUSEL OIL, and RECT. NAPHTHA, NEWS THE CHEMICAL NEWS. VOL. XXXIX. No. 1016. RECENT CONTRIBUTIONS TO THE HISTORY By Professor ABEL, C.B. F.R.S. IN comparing the effects of these nitro-glycerin preparations with each other and with compressed guncotton and preparations of it, by detonating equal quantities quite unconfined upon iron plates, the results appear to establish great superiority, in point of violence of action, or destructive effect, of the more rigid explosive agents (the gun-cotton preparations). Thus, employing iron plates 1 inch thick (supported upon an anvil with a central cavity), and 4 ozs. of each material unconfined, the charges being all about the same diameter, exploded by detonators of equal strength, and simply resting upon the upper surface of the plate, compressed gun-cotton produced a considerable indentation of the upper surface of the plate, and long cracks in the lower surface; a species of nitrated gun-cotton, called tonite, produced a much shallower indentation, though still a very marked one, but did not crack the lower surface. Dynamite produced only a very slight impression upon the plate, and none could be detected by the eye on the plate upon which the blasting gelatin was exploded. The difficulties, brought out by past experience, which attend the contrivance of really comparative tests of the explosive power of such substances as those under discussion, is well exemplified by the foregoing results, which were influenced to the maximum extent by the physical characters of the several substances when applied, as they were upon these iron plates, in a perfectly unconfined condition, so that the particles were free to yield to the force of the initiative detonation in proportion to their mobility. But, for this very reason, these experiments afford excellent illustration of the extent to which the development of detonation and the sharpness of its transmission through the mass is influenced not only by the inherent sensitiveness of the substance to detonation (or by its chemical instability) but also by the degree of proneness of their particles to yield mechanically to the force of a blow as applied by an initiative detonation. Thus, although in comparing two substances of similar physical characters, compressed gun-cotton and compressed nitrated gun-cotton or tonite, the superiority of the pure compound over the mixture, in point of sharpness and violence of action, is well illustrated, a comparison of the result furnished by the weakest of the four explosive agents tried, viz. tonite, with that of the substance which should be superior to all the others in explosive force (i.e. the blasting gelatin) demonstrates the important influence which the comparatively great rigidity of the mass in the one case exerts in favouring the completeness and sharpness of its detonation in open air, and the great disadvantage under which the other explosive is applied, arising out of the plastic and therefore readily yielding nature of the material. But if, by exposure to a moderate degree of cold, this plastic nitro-glycerin preparation is made to freeze (for it partakes of the property of the liquid itself of freezing at a temperature above the freezing-point of water, and becomes thereby converted into at least as rigid a substance as the two descriptions of gun-cotton) its detonation upon an iron plate produces an indentation, as well as a destructive effect upon the lower surface of the plate, very decidedly greater than those furnished by * Abstract of a Paper read before the Royal Institution of Great Britain, Friday, March 21, 1879. Similarly, the effect produced by the detonation of dynathe corresponding amount of pure compressed gun-cotton. mite upon a plate of the kind used, is but little inferior to that of gun-cotton, and decidedly greater than that of tonite, if it is employed in the frozen condition. A series of experiments has been made with cylinders of lead having a central perforation 13 inches in diameter beneath of a thickness ranging from 3.5 to 5'5 inches, extending to a depth of 7 inches and leaving solid metal according to the size of the cylinders used. These furnished results of considerable interest as illustrating the action of these several detonating agents. Charges of 1.25 ozs. of each explosive substance were used throughout the experiments, and were placed at the bottom of the holes. By the detonation of the charges the cylindrical holes in the lead were enlarged into cavities of a pear shape (and sometimes approaching the spherical form), of various diameters; in some instances ths metal was besides partially torn open in a line from the bottom of the charge-hole to the circumference of the lower face of the cylinder; and in the case of some of the gun-cotton charges, the fissure in the metal in this direction was complete, the base of the block being separated from the remainder, in the form of a cone. portions of the holes above the charges were simply left In the first place the open; in the subsequent experiments they were filled up to a level with the upper surface, with dry, fine, loose sand, or with water. The dimensions of the cylinders were increased in successive experiments until, in the case of every one of the explosives used, the mass of metal was sufficiently great to resist actual fracture at the base of the cylinder. Under the conditions of these experiments, more or less considerable resistance being opposed to the mechanical dispersion of the plastic explosive substances, their detonation was greatly facilitated, though even then the holes in the lead blocks being left open to the air, some amount of the blasting gelatin evidently escaped detonation; the widening of the upper part of the charge-hole in experiments of this nature made with the gelatin indicated that detonation was transmitted to small portions dispersed in the first instance and in the act of escaping from the block. In all the experiments, whether the holes were left open or filled with sand or water, the effect produced upon the base of the block by the detonation of compressed gun-cotton was considerably more violent than with the other explosive agents, indicating a sharpness of action which was only shared by the blasting gelatin when used in a frozen state in one of these experiments. The dimensions of the cavities produced by the gelatin were, at the largest part, considerably greater than those produced by the dynamite and nitrated gun-cotton (tonite), and slightly greater than those of the gun-cotton charges; but in the latter, the fracture of the base of the cylinder gave rise in most of the experiments to an escape of force, so that in these cases the effects of the detonation could not be well compared by measurements of the cavities. When the gelatin was converted by freezing into a rigid mass its superiority in explosive force even over compressed gun-cotton was well illustrated; the base of the lead block was all but blown out, the cavity produced was considerably the largest, and the suddenness and violence with which motion was imparted to the water tamping caused the top of the block also to be blown off in the form of a cone. An excellent illustration was obtained by comparing this result with those furnished by the gelatin in its normal plastic state of the influence exercised by the physical condition of an explosive substance upon the rapidity and completeness with which detonation is transmitted through its mass. The difficulties attending the application of blasting gelatin, in some directions in which explosive agents are applied, on account of the uncertainty attending the development of its explosive force, even with the use of a comparatively powerful detonator, unless it be very strongly confined, has led to attempts to reduce its non-sensitive 210 History of Detonating Agents. ness to detonation by mixing it with materials intended Lastly, its explosive force appears to be in no way diminished by this modification of its composition, on the contrary, its superiority in this respect to compressed gun-cotton becomes more manifest, as demonstrated by some of the experiments with lead blocks, while its action partakes of that sharpness peculiar to the detonation of the rigid gun-cotton, as indicated by the fissure of that part of the metal situated beneath the charge. Finely divided cotton fibre has a similar effect to trinitro-cellulose in modifying the physical character and increasing the sensitiveness to detonation of the blasting gelatin, but its explosive force is, of course, proportionately reduced with its dilution with an inert substance. May 16, 1879. to service exigences, approaching that of wet compressed gun-cotton. The camphoretted gelatin still labours, however, under the disadvantage of being readily inflammable, and of burning fiercely, and consequently of giving rise, like dynamite and dry gun-cotton, to violent explosion or detonation, if burned in considerable bulk; a result which was explained by the lecturer in his discourse delivered at the Royal Institution in 1872. Moreover, the camphoretted blasting gelatin is so difficult of detonation by the means ordinarily applied, that a large initiative charge of a very violent detonating mixture consisting of pure specially prepared trinitro-cellulose and nitro-glycerin is prescribed by the Austrian experimenters as being indispensable to its proper detonation. The action of camphor and of other substances rich in carbon and hydrogen in reducing greatly the sensitiveness to detonation of the preparation of soluble gun-cotton and nitro-glycerin, is not to be traced to any physical modification of that material produced by the addition of such substances, and no satisfactory theory can at present be advanced to account for it on chemical grounds. The camphoretted gelatin, like Nobel's original gelatin itself, may be kept immersed in water for a considerable time without any important change; the surface of the mass thus immersed becomes white and opaque, apparently in consequence of some small absorption of water, but no nitro-glycerin is separated, and on re-exposure to the air the material gradually assumes once more its original aspect. It has consequently been proposed to render the storage of blasting gelatin comparatively safe by keeping it immersed in water till required for use, but the test of time is still needed to establish the unalterableness of the material under this condition. There can be little question that this interesting nitroglycerin preparation, either in its most simple form or modified in various ways by the addition of other ingredients, promises, by virtue of its great peculiarities as a detonating agent, to present means for importantly extending the application of nitro-glycerin to industrial purposes; and it is not improbable that through its agency this most violent of all explosive agents at present producible upon a large scale may also come to acquire special value for important war purposes. It has been pointed out that the complete solidification by freezing of plastic preparations containing nitro Nobel has made the interesting observation that an addition to the blasting gelatin of small proportions of certain substances rich in carbon and hydrogen, which are soluble in nitro-glycerin, such as benzol and nitrobenzol, increases to a remarkable extent the non-sensitive-glycerin, such as dynamite and the blasting gelatin, has ness to detonation of the original material; and this observation has led to experiments being conducted by engineer officers in Austria, with a view of endeavouring to convert the blasting gelatin into a material which should compete, as regards some special advantages in point of safety, with wet gun-cotton in its application to military and naval purposes, and especially as regards non-liability to detonation or explosion by the impact of rifle bullets. If boxes containing dry compressed guncotton are fired into from small arms even at a short range, the gun-cotton is generally inflamed, but has never been known to explode; the sharpness of the blow essential to the latter result, which the bullet might otherwise give, being diminished by its penetration through the side of the box before reaching the explosive. It is scarcely necessary to state that wet gun-cotton, containing even as little as 15 per cent of water, is never inflamed under these conditions. On the other hand, dynamite is invariably detonated when struck by a bullet on passing through the side of the box, and blasting gelatin, though so much less sensitive than dynamite, behaves in the same way in its ordinary as well as in the frozen condiThe Austrian experiments indicated that the gelatin when intimately mixed with only 1 per cent of camphor, generally, though not invariably, escaped explosion by the impact of a bullet, but that when the proportion of camphor amounted to 4 per cent the material was neither exploded nor inflamed, though, in the frozen state, it was still liable to occasional explosion. These results were considered indicative of a degree of safety in regard tion. | the effect of facilitating the transmission of detonation throughout the mass, and of thus developing or increasing the violence of their action, under certain conditions of their applications, i.e., when they are either freely exposed to air or not very closely or rigidly confined. But while, under circumstances favourable to the detonation of these substances, when in the frozen state, their full explosive force is thus much more readily applied than when they are in their normal (thawed) condition, the frozen substances are less sensitive to detonation by a blow or an initiative detonation. On the other hand, if subjected to the rapid application of great heat (as, for example, by the burning of portions of a mass of the explosive substance itself), a detonation is much more readily brought about with the frozen material than if it be in its normal condition. Thus a package containing 50 lbs. of cartridges of plastic dynamite when surrounded by fire burned away without any indication of explosive action; on submitting 10 lbs. of frozen dynamite to the same treatment that quantity also burned without explosion, though at one time the combustion was so fierce as to indicate an approach to explosive action; but when the experiment was repeated on the same occasion with 15 lbs. frozen dynamite a very violent detonation took place after the material had been burning for a short time, a deep crater being produced in the ground beneath. The following is offered as the most probable explanation of this result. When a mass of dynamite, as in these cartridges, is exposed to sufficient cold to cause the nitro-glycerin to freeze, it does not become uniformly hardened throughout, partly because of slight variations | in the proportion of nitro-glycerin in different portions of the mixture composing the cartridge, and partly because unless the exposure to cold be very prolonged the external portions of the cartridges will be frozen harder or more thoroughly than the interior. It may thus arise that porrtions of only partially frozen or still unfrozen dynamite may be more or less completely enclosed in hard crusts, or strong envelopes, of perfectly frozen and comparatively very cold dynamite. On exposure of such cartridges to a fierce heat very rapidly applied, as would result from the burning of a considerable quantity of the material, some portion of one or other of the cartridges would be likely to be much more readily raised to the igniting or exploding point than the remaining more perfectly frozen part in which it is partly or completely imbedded. If the ignition of this portion be brought about (which it will be with a rapidity proportionate to the intensity of heat to which the cartridge is exposed), the envelope of hard frozen dynamite by which it is still more or less completely surrounded and strongly confined, will operate like the metal envelope of a detonator, in developing the initial pressure essential for the sudden raising of the more readily inflammable portion of the dynamite to the temperature necessary for the sudden transformation of the nitro-glycerin into gas, and will thus bring about the detonation of a portion of the cartridge, which will act as the initiative detonator to the remainder of the dynamite. | On igniting separately, at one of their extremities, some dynamite cartridges which had been buried in snow for a considerable period, the lecturer has observed that, as the frozen material gradually burned away, very slight | but sharp explosions (like the snapping of a small percussion cap on a gun nipple) occurred from time to time, portions of the frozen dynamite being scattered with some violence. He did not succeed in obtaining actual detonation by thus burning frozen cartridges surrounded by others in a similar condition, but he has been informed by Mr. McRoberts, of the Ardeer Dynamite Works, that he has more than once detonated a small heap of hardfrozen cartridges, weighing altogether 1 lb., by igniting one cartridge which was surrounded by the remainder. These facts appear to substantiate the correctness of the foregoing explanation. They point to the danger of assuming that, because dynamite in the frozen state is less sensitive to the effects of a blow or initiative detonation than the thawed material, it may therefore be submitted without special care to the action of heat, for the purpose of thawing it. Instances of the detonation, with disastrous results, of even single cartridges of frozen dynamite, through the incautious application of considerable heat (as, for example, by placing them in an oven, or close to a fire), have been, and are still, of not unfrequent occurrence, even though Mr. Nobel has insisted upon the application of heat through the agency only of warm water, as the sole reliable method of safely thawing dynamite cartridges. While the sensitiveness to detonation of air-dry guncotton remains unaffected by great reduction in temperature of the mass, and while in this respect it presents advantages over nitro-glycerin preparations, wet guncotton becomes very decidedly more susceptible to detonation when frozen. Thus the detonation of gun-cotton containing an addition of from 10 to 12 per cent of water is somewhat uncertain with the employment of 100 grs. of strongly-confined fulminate, and 200 grs. are required for the detonation of the substance when containing 15 to to 17 per cent of water; but the latter in a frozen state can be detonated by means of 30 grs. of fulminate, and 15 grs. are just upon the margin of the amount requisite for detonating with certainty frozen gun-cotton containing 10 to 12 per cent of water. The deadening effect of solid water upon the sensitiveness of gun-cotton to detonation is, in fact, intermediate between those of a liquid and of inert solid substances. The effects produced and products formed by the explo sion of gun-cotton in perfectly closed spaces, both in the loose and the compressed form, and by its detonation in the dry and the wet state, have been made the subject of study by Captain Noble and Mr. Abel, the method of research pursued being the same as that followed in their published researches on fired gunpowder; results of considerable interest in regard to the heat of explosion, the pressures developed, and the products of explosion of dry and wet gun-cotton have been obtained, which are about to be communicated to the Royal Society. It may briefly be stated that the temperature of explosion of gun-cotton is more than double that of gunpowder (being about 4400° C.); that the tension of the products of explosion, assuming the material to fill entirely the space in which it is fired, is considerably more than double that of the powder-products under the same conditions; that the products obtained by the explosion of dry guncotton are comparatively simple and very uniform under different conditions as regards pressure; that the products of detonation of dry gun-cotton do not differ materially from those of its explosion in a confined space, but that those furnished by the detonation of wet gun-cotton present some interesting points of difference. Messrs. Noble and Abel are extending their investigations to the nitroglycerin preparations. The great advance which has been made within the last twelve years in our knowledge of the conditions which determine the character of the metamorphosis that explosive substances undergo, and which develop or control the violence of their action, finds its parallel in the progress which has been made in the production, perfection, and application of the two most prominent of modern explosive agents, nitro-glycerin and gun-cotton. Discovered at nearly the same time, less than forty years ago, the one speedily attained great prominence on account of the apparent ease with which it could be prepared and put to practical use; a prominence short-lived, however, because the first, and somewhat rash, attempts to utilise it preceded the acquisition of sound and sufficient knowledge of its nature and properties. Even many years afterwards, when the difficulties attending its employment appeared to have have, been surmounted, the confidence of its most indefatigable partisans and staunchest friends received a rude shock, from which it needed the support of much faith and some fortitude to recover. Meanwhile, the other substance, which now shares with it the honours of important victories won over gunpowder, continued to be generally regarded as a dangerous chemical curiosity, even for some time after its present position as one of the most important industrial products and useful explosive agents was being gradually but firmly secured for it, step by step, by the talent and untiring energy of a single individual. Almost from the day of its discovery, the fortunes of gun-cotton continued to fluctuate, and much adversity marked its career, until at last its properties became well understood, and its position as a most formidable explosive agent, applicable on a large scale, with ease, great simplicity, and with a degree of safety far greater than that as yet possessed by any other substance of this class, has now become thoroughly established. Since the lecturer last discoursed on the properties of gun-cotton, seven years ago, this material has attained a firm footing as one of the most formidable agents of defence and offence. For all military engineering operations, and for employment in submarine mines and torpedoes, compressed gun-cotton, stored and used in the wet condition, has become the accepted explosive agent in Great Britain; within the last five years upwards of 550 tons have been manufactured for this purpose, and are distributed over our chief naval stations at home and abroad. Germany some years since copied our system of manufacture and use of gun-cotton; France has provided itself with a large supply for the same purposes; and Austria, where the acquisition of bitter experience of the uncer |