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time of Descartes and Leibnitz, when physical science and moral philosophy went hand in hand, to find an equivalent.

But it must be allowed that the science of Thermodynamics may be treated with advantage from this double point of view; for, after its First Law has been established, that heat and work are equivalent and interchangeable, the rate of exchange being fixed by the mechanical equivalent of Joule and Hirn, when we come to the Second Law, named after Carnot, we are compelled to secure conviction of its truth by an appeal to the arguments of analogy and metaphysics.

Hirn spent the last years of his life at Colmar, in the society of a few congenial friends, much interested in metaphysics and meteorology, but cut off from his native France by international strained relations.

In this age of practical Thermodynamics his work will not be lost sight of; but we are still far from a complete reconciliation of the abstract theories of the books and the observed realities of practice.

NOTES.

A. G. GREENHILL.

THE Croonian Lecture, which will be delivered before the Royal Society on February 27 by Prof. Marshall Ward, will be on "The Relations between Host and Parasite in certain Epidemic Diseases of Plants."

ON Thursday last the Astronomer-Royal was elected by ballot to fill the place of the late Father Perry upon the Council of the Royal Society.

METEOROLOGISTS will be sorry to hear of the death of Prof. C. H. D. Buys-Ballot, on Sunday last. He was born in 1817, and had been Director of the Meteorological Institute, Utrecht, for more than 30 years.

DR. DAVID SHARP, the eminent entomologist, and late President of the Entomological Society of London, has accepted the appointment of Curator in Zoology in the Museum of the University of Cambridge, rendered vacant by the resignation of the Rev. A. H. Cooke, whose labours on the Macandrew Collection in that Museum have been so highly appreciated by conchologists.

SIR WILLIAM GULL, F.R.S., was so distinguished a physician, and his name was so well known, that the tidings of his death excited a widespread feeling of regret. He died on Wednesday, January 29, from paralysis, and the funeral took place on Monday at the churchyard of Thorpe-le-Soken, Essex. He was in his seventy-fifth year.

WE regret to hear of the death of Dr. L. Taczanowski, which took place at Warsaw on January 11. He is best known for his standard work "Ornithologie du Pérou," but his contributions to the ornithology of Poland, of Siberia, and the Corea have also been numerous and important.

GERMAN papers announce the death of Otto Rosenberger, the well-known astronomer. He was born in Courland in 1810, and in 1831 was appointed to the charge of the Observatory at Halle, and at the same time was made Professor of Mathematics. This position he held during the rest of his long life. Rosenberger's name is known chiefly in association with his work relating to Halley's comet.

ANOTHER death which we are sorry to have to record is that of Prof. Neumayr, the geologist, of Vienna. He was only a little over forty years of age, and his death is a great loss.

ON February 15, Lord Rayleigh will begin a course of seven lectures at the Royal Institution. The subject will be electricity and magnetism.

THE Council of the Society of Arts have arranged that a course of lectures on "The Atmosphere" shall be given by Prof. V. Lewes on the following Saturday afternoons: March 8, 15, 22, and 29, at 3 o'clock.

MR. B. A. GOULD, Cambridge, Mass., has been appointed President of the American Metrological Society for the present year. Among the members of the Council of this Society Messrs. Cleveland Abbe, H. A. Newton, Simon Newcom and S. P. Langley. The Society was founded in 1873, and . objects are to improve existing systems of weights, measures, and moneys, and to bring them into relations of simple com mensurability with each other; to secure the universal adoption of common units of measure for quantities in physical observa tion or investigation, for which ordinary systems of metrology do not provide; to secure uniform usage as to standard points reference, or physical conditions to which observations must be reduced for purposes of comparison; and to secure the use of the decimal system for denominations of weight, measure, 201 money derived from unit-bases, not necessarily excluding for practical purposes binary or other convenient divisions.

THE Committee of the Cambridge University Antiquarian Society in their fifth Annual Report state that, since the opening of the Archæological Museum in 1884, over 2800 objects and 900 books have been added to the collection. The most im portant additions have been made in the ethnological department including (during the past year) General Scratchley's collectionfrom New Guinea, a series of 500 specimens of implements and ornaments from the West Indies, presented by Colossi Fielden, who has also given many rare stone implements an weapons collected in South Africa, and a series of 70 specimers of dresses, weapons, &c., from the Solomon and Banks Islands and from Santa Cruz, presented by Bishop Selwyn. The Curato Baron von Hügel, reports that during the long vacation he excavated with success a Roman refuse-pit and a burial-place a the eastern side of Alderney. The digging is to be resumed. THE seventh annual dinner of the Association of Pr Sanitary Inspectors was held on Saturday evening at the Fir Avenue Hotel, Holborn. Dr. B. W. Richardson presided, an proposed the toast of "The Association and its President S Edwin Chadwick." The duties of the Association, he sai were to teach and protect its members, and all sanitary insp tors ought to belong to it. He hoped that the apathy at present shown by too many of them would not last any longer.

DR. A. N. BERLESE, of Padua, has been appointed Profess of Botany to the Royal Lyceum at Ascoli-Piceno; and Dr. ! H. Wakker, of Utrecht, Professor of Botany at the dairy school at Oudshoorn, Holland.

THE Botanical Gazette published at Crawfordsville, Indiana gives some particulars of one of the most magnificent bequests ever made for scientific purposes, that of the late Mr. H. Shiw for the endowment of the Botanic Garden and School of Ewary at St. Louis, Missouri, amounting to not less than between three and five million dollars. The trustees have determined to apply the income to the maintenance and increase in the scienti usefulness of the Botanic Garden; to provide fire-proof quaners for the invaluable herbarium of the late Dr. George Engelmann. and to supply means for its enlargement; to secure a botanica! museum; and to gradually acquire and utilize facilities i research in vegetable physiology and histology, the diseases and injuries of plants, and other branches of botany and hort culture. To aid in the carrying out of this last purp travelling botanical scholarships have been established. The present very able director of the Botanic Garden is Dr. Willia Trelease.

THE Kew Bulletin for February begins with some extracts from the Annual Report on the Government cinchona plantation and factory in Bengal for the year 1888-89. The valuable information presented in these extracts is given for the benefit of persons growing cinchona in countries which the documents for the Government of Bengal are little likely to reach. The new number also deals with the use of maqui berries for the colouring of wine, vine-culture in Tunis, phylloxera in Victoria, the botanical exploration of Cuba, and the sugar production of the world. The section on the last of these subjects relates to statistics brought together in Dr. Robert Giffen's report on the progress of the sugar trade. Commenting on the figures supplied in this report, the writer in the Bulletin says that if they "do not justify a gloomy view of the present position of the cane-sugar industry in British colonies, they scarcely justify a very optimstic one. It is obvious that the capital which should be applied to the improvement of manufacturing processes and machinery under present circumstances, practically diverted to the mere muntenance of the cultivation. And this in the long run must be a losing game. At present the fact stands that West Indian sugar has to a large extent been driven from the home market 'o 'hat of the United States. If in time it should lose that, its inte apparently is sealed."

AT the last meeting of the Paris Biological Society, Prof. Raphael Blanchard gave an interesting account of a peculiar pigment, hitherto found in plants only, carotine, which he has discovered in a crustacean in one of the Alpine lakes, near Briançon. Its functions are not yet known, but M. Blanchard otends to pursue his study of the subject on the spot. The animals cannot be transported alive to lower levels.

We are glad to welcome the first number of The University Extension Journal. The Society by which it is issued has become important enough to need an organ of its own; and the new periodical, which will appear at the beginning of every month, ought to be of service to all who are in any way #terested in the movement.

THE Engineer of January 31 contains a leading article on 'Colour-blind Engine-drivers," and it is interesting to note bar the leading technical journal has to say on the subject: We do not say that no accident was ever brought about by the inability of a driver to distinguish between a green light and a red one, but we can say that nothing of such an accident is to le met with in the Board of Trade Reports." Our contemporary of opinion that the testing of the sight of locomotive men hould be made under working conditions, i.e. with actual signal lights.

A PAPER on mortality from snake bite in the district of Katnagherry was read lately before the Bombay Natural History Society by Mr. Vidal, of the Bombay Civil Service. Many of be deaths in that district are, he says, due to a small and ingnificant-looking snake, called "foorsa" by the natives. It sa viper rarely more than a foot long, and is so sluggish that it does not move out of the way till trodden on. Thus it is much more dangerous than the stronger and fiercer cobra.

DURING the year 1889 no fewer than 28 bears, 115 wolves, and 45 wolf-cubs were shot in the single district of Travnik, in Bosnia.

Das Wetter for January contains:-(a) An article by Dr. R. Assmann on climatological considerations about the prevalent epidemic of influenza. From an experience of many years in dealing with the connection between climatic conditions and the state of health, the author gives the following conditions as the most favourable for spreading organisms in the air: (1) dry

ness of the soil, (2) deficiency of snow covering, (3) deficiency of rainfall, (4) existence of fog or low-hanging clouds, (5) prevalence of high barometer with a small intermingling of air in the vertical direction; and he shows that these conditions were prevalent in Eastern and Central Europe from the beginning of November; that atmospheric dust existed in great quantities, and was propagated westward by easterly, north-easterly, and south-easterly winds. He considers that changes of temperature had no important relation to the spread of the epidemic. (b) A lecture recently delivered to the Scientific Club in Vienna, on the general circulation of the atmosphere, by Dr. J. M. Pernter. He refers to the idea of the conflict of polar and equatorial winds so long supported by Dove and others, and shows that the publication of synoptic charts since the year 1863 has demonstrated that the above theory does not hold good for temperate and northern latitudes, that the circulation there depends upon the positions of the areas of high and low pressures, producing cyclones and anticyclones. Many dark points require explanation, such as the tracks which the cyclones follow, but much new light has recently been thrown upon the subject, especially by the researches of Ferrel, Oberbeck, and Abercromby.

DR. ALBRECHT PENCK, Professor of Physical Geography at the University of Vienna, lately called attention to the fact that no two official accounts of the area of the Austro-Hungarian monarchy agree. The difference between the highest and the lowest estimates amounts to 3313'75 square kilometres. By an examination of the new special map constructed by the Army Geographical Institute, which is on the scale of 1 to 75,000, and occupies 400 sheets, Prof. Penck has satisfied himself that the actual area of the Empire is 3247'12 square kilometres greater than is given in the latest published official account. The error arose chiefly from an incorrect triangulation of the Hungarian portion of the Empire, which is 3054'02 square kilometres larger than has been supposed.

IT has hitherto been generally believed that the Montgolfier or hot-air balloon cannot be used in tropical climates. If this were true, ballooning for war purposes would of course be imWe possible in places where coal-gas could not be obtained. learn from the Times that Mr. Percival Spencer, who has been making a series of interesting balloon experiments in Central India, has succeeded in showing that the theory is without foundation. At Secunderabad, in presence of the garrison and a crowd of European and native spectators, he lately made an ascent in his patent asbestos balloon. The inflation was effected by the burning of methylated spirit inside the balloon, which was held in place by 25 soldiers of the Bedford regiment until the word to "let go" was given. After rising to a considerable height, the aeronaut descended by means of his parachute. The spot where the ascent was made is over 2000 feet above the level of the sea, and the achievement was all the more remarkable because of the sultry climate and the great rarity of the air. AN interesting paper on 66 Midlands," by Mr. Edwin A. Walford, has been reprinted from Some Terraced Hill Slopes of the the Journal of the Northamptonshire Natural History Society. The factors in the formation of these terraced slopes Mr. Walford groups as follows:-(1) The slipping and sliding outwards of the saturated porous marls upon the tenacious clays at the line of drainage, aided doubtless by the pressure of the superincumbent rock bed. (2) Displacements caused by the removal by chemical and mechanical solution of certain constituents of the marls and marlstone by the passage of the surface water through them. (3) The siiding downwards of the surface soil, as described by Dr. Darwin, and latterly illustrated by Mr. A. Ernst. The suggestions offered by Mr. Walford agree in the main, as he himself points out, with those adopted by Mr. A. Ernst in his paper in NATURE, February 28, 1889.

MESSRS. GAUTHIER-VILLARS (Paris) have recently added three new works to their already large list of photographic treatises. One is the "Manuel de Phototypie," by M. Bonnet, giving full details of the various processes for the rapid reproduction of photographs, such as is now demanded for many purposes. The formulæ are stated very clearly, and the apparatus required is sufficiently illustrated by diagrams. The treatise is thoroughly practical, and will be very valuable to all interested in the subject, whether as amateurs or for trade purposes. The second-"Temps de Pose" is by M. Pluvinel, and deals with the difficult question of the time of exposure. It is shown that what is generally regarded as a rule-of-thumb process can be reduced to a scientific one. The various functions of the duration of the exposure are first considered mathematically, and it is then shown how the results of the investigations are to be applied practically, the method being illustrated by worked-out examples. To simplify matters, tables are given showing the different elements, such as coefficient of brightness, for all ordinary photographic subjects. The treatise is chiefly interesting as a scientific contribution, as few photographers will care to take the trouble of working out the time of exposure, now that they have found that good work can be done by judgment alone. The third book is in two volumes, and treats of the various "film" processes ("Procédés Pelliculaires," by George Balagny). It claims to give a full account of all that has been said and done in connection with the subject since the introduction of photography, and as far as we can judge, this claim is fully justified. Every detail of the subject is considered in a very practical manner. One of the most interesting applications of flexible films mentioned is the registration of flash signals in "optical telegraphy."

THE "Year-book of Photography" (Piper and Castle) for 1890 fully bears out the good reputation gained by its predecessors. In addition to the information relating to the various photographic societies, there are several articles on the advances in photographic processes which have been made during the past year, and other useful notes. One of the most interesting articles is that by the editor on photography in natural colours, from which we learn that "processes of practical value, to achieve the end, are likely to be discovered by the exercise of ability and perseverance." The only important omission we notice is a record of the remarkable achievements in astronomical photography. The volume contains a portrait and short biographical notice of Edmond Becquerel. The whole forms an invaluable book of reference to all photographic matters, with the exception

referred to.

MESSRS. GEORGE BELL AND SONS have published "The School Calendar and Hand-book of Examinations, Scholarships, and Exhibitions, 1890." This is the fourth year of issue, and great pains have been taken, as in former years, to secure that the information brought together shall be full and trustworthy. A preface is contributed by Mr. F. Storr.

THE sixteenth part of Cassell's "New Popular Educator" has been issued. It includes a map of Australasia.

THE Proceedings of the International Zoological Congress, held in Paris last summer, will be ready for distribution in a fortnight.

A NEW and very simple method of synthesizing indigo has been discovered by Dr. Flimm, of Darmstadt (Ber, deut. chem. Ges., No. 1, 1890, p. 57). In studying the action of caustic alkalies upon the monobromine derivative of acetanilide, CH.NH.CO.CH,Br, a solid melting at 131°5, it was found that when this substance was fused with caustic potash a product was obtained which at once gave an indigo blue colour on the addition of water, and quite a considerable quantity of a blue solid resembling indigo separated out. The best mode of carrying out the operation is described by Dr. Flimm as follows:-The

monobromacetanilide is carefully mixed with dry caustic potash v a mortar, and the mixture introduced into a retort and hear rapidly until a homogeneous reddish-brown melt is altame This is subsequently dissolved in water, and a little ammo or ammonium chloride solution added, when the liquid in mediately becomes coloured green, which colour rapidly change into a dark blue, and in a short time the blue colouring matte is for the most part deposited upon the bottom of the vesse which the operation is performed. The fused mass may n conveniently be dissolved in dilute hydrochloric acid, and a little ferric chloride added, when the formation of indigo tak place immediately. The collected blue colouring matter m be readily obtained pure by washing first with dilute hydrochlong acid and afterwards with alcohol. That this blue substance wi really common indigo was proved by the fact that it yielded several of the most characteristic reactions of indigotin, such solubility in aniline, paraffin, and chloroform, its sublimat and the formation of sulphonic acids, which gave similar change of colour with nitric acid to those of indigotin. The final pr was afforded by its reduction to indigo white and re-oxidation: indigo blue by exposure to air. Moreover, the absorptat spectrum of the colouring matter was found to be identical wit the well-known absorption spectrum of indigo. Hence the can be no doubt that indigo is really formed by this very simp* process. The chemical changes occurring in the reaction are ou sidered by Dr. Flimm to be the following:-Indigo blue i ne produced directly, but first, as a condensation product of th NH CH, 2

monobromacetanilide, indoxyl is formed, CH,

COн

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NH

C=C

H

NH by oxidation into indigo, CH. CO CO two molecules each losing two atoms of hydrogen by oxidatio and then condensing to form indigo. It was not found poss to isolate the intermediate pseudo-indoxyl, owing to its extreme instability; indeed, the all-important point to be observed in the practical carrying out of the synthesis by this method is that is fusion must be performed quickly and the temperature raised rapidly to a considerable height, the whole process occupy. only a few minutes. The yield of pure indigo under the cr ditions yet investigated is not very large, amounting to at four per cent. of the weight of the original anilide.

THE additions to the Zoological Society's Gardens during the past week include thirteen Cuning's Octodons (Octodon cuanfrom Chili, presented by Mr. W. H. Newman; five Com : Dormice (Muscardinus avellanarius), British, presented by M Florance Wyndham; a Large Hill-Mynah (Gracula intermila from India, deposited; a Dingo (Canis dingo), born in the Gardens.

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Remarks.

(1) The spectrum of this nebula has not yet, so far as I know, been recorded, but the observation will not be difficult, if one may judge from the description given by Herschel, namely: Very bright, pretty large, round, much brighter in the middle, mottled as if with stars."

2) This star has a spectrum of the Group II. type, Dunér describing it as very beautiful. He states that all the bands, 1-9, are very wide and dark. The observations most likely to xtend our knowledge of the group of bodies to which this star telungs are (1) observations of the bright carbon flutings (see p. 305); (2) comparisons with the flame spectra of manganese, magnesium, and lead; (3) observations made with special reference to the presence or absence of absorption lines, of which Junér makes no mention.

3) Gothard classes this with stars of the solar type. The adal differential observations are required.

(4) A star of Group IV. The usual observations of the reative intensities of the hydrogen and metallic lines (b, D, &c.), as compared with other stars, are required.

5) A rather faint star of Group VI., in which the character *y band 6 (near A 564), as compared with the other carbon bands 9 and 10), requires further attention. Secondary bands should 10 be looked for.

6) This variable is stated by Gore to have a continuous pectrum, but it seems probable that lines or flutings will be found if the star be examined under the most favourable conht ons-that is, when near maximum. Rigel was formerly said to have a continuous" spectrum, but the lines are now by no ricans difficult to se. The star ranges from magnitude 6 at raaximum to 7:2 at minimum, and the period is 31-50 days Mure). A. FOWLER.

TUTAL SOLAR ECLIPSE OF 1886.-Dr. Schuster has thus mmarized the spectroscopic results he obtained at this eclipse Phil. Trans., vol. 180, 1889) :

1) The continuous spectrum of the corona has the maximum actinic intensity displaced considerably towards the red, when compared with the spectrum of sunlight.

2) While, on the two previous occasions on which photographs of the spectrum were obtained, lines showed themselves utside the limits of the corona, this was not the case in 1886. 3) Calcium and hydrogen do not form part of the normal petrum of the corona. The hydrogen lines are visible only the parts overlying strong prominences; the H and K lines alcium, though visible everywhere, are stronger on that side of the corona which has many prominences at its base.

4) The strongest corona line in 1886 was at λ = 42328; this probably the 42330 line often observed by Young in the aromosphere.

5) Of the other strong lines, the positions of the following sem pretty well established:

4056 7 4084-2 4089 3 4169-7 4195 0 4211.8 4280 6 4365 4 4372 2 4378'1 4485'6 4627'9

The lines printed in thicker type have been observed also at the Caroline Island and Egyptian Eclipses.

16) A comparison between the lines of the corona and the laes of terrestrial elements has led to negative results.

ANNUAIRE DU BUREAU DES LONGITUDES.-In the volume for 18, MM. Loewy and Schulhof contribute a list of the comets which appeared from 1825 to 1835 inclusive, and in 1888, being a continuation of the lists given in former years. M. Loewy also gives a complete table of the appearances of the planets throughout 1890, and ephemerides of a considerable number of varable stars. An elaborate comparison of the various calendars is from the pen of M. Cornu, and under the head of the solar system a nich store of information is included. With the notices we bad an account of the meeting of the permanent committee of the photographic chart of the heavens and the Photographic Congress of September last. This year's Annuaire is as compietely filled with information as it has ever been and doubtless will be as much appreciated by astronomers.

ANNUAIRE DE L'OBSERVATOIRE ROYAL DE BRUXELLES.The volume for 1890 is the fifty-seventh annual publication from this Observatory. It contains tables of the mean positions of the principal stars and their apparent right ascensions, of the occultaion of stars by the moon, and of eclipses of Jupiter's satellites, mestion being also made of remarkable phenomena relating to the moon and the planets. M. Folie gives a biographical

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GEOGRAPHICAL NOTES.

BARON NORDENSKIÖLD has announced in the Swedish Academy of Sciences, that he and Baron Oscar Dickson, with assistance from the Australian colonies, will start on an expedition in the South Polar regions next year.

A RECENT telegram from Tashkent announced that Colonel Pevtsoff and M. Roborovsky had discovered a convenient pass to the north-western part of Tibet, from Nia, and had mounted to the great table-land. The plateau has there an altitude of 12,000 feet above the sea, and the country round is desolate and uninhabited, while towards the south the plateau is well watered and wooded. The Tashkent telegram is so expressed that it might be supposed to mean that two separate passes had been discovered by the two explorers. But the news received from the expedition at St. Petersburg on December 26, and dated October 27, shows that both explorers proposed to leave the oasis of Keria (100 miles to the east of Khotan) on the next day, for Nia (65 miles further east) and there to search for a passage across the border-ridge which received from Prjevalsky the name of the "Russian ridge." This immense snow-clad chain separates the deserts of Eastern Turkestan from the trapezoidal space, the interior of which is quite unknown yet, and which is bordered by the "Russian" ridge and the Altyn-tagh in the north-west; the ridges of Tsaidam and those named by Prjevalsky"Columbus and "Marco-Polo" in the north-east; the highlands (explored by Prjevalsky in 1879-80) at the sources of the Blue River, in the south-east; and a long, yet unnamed ridge which seems to be a prolongation of the Tan-la, in the south-west. leading to that plateau from Nia, and now discovered by the Russian expedition, is situated some 80 miles to the east of the well-known pass across the Kuen-lun Mountains which leads from Southern Khotan to Lake Yashi-kul. M. Roborovsky's intention is evidently next to move up the Tchertchen river and to endeavour to reach the ridges "Moscow " and "Lake Unfreezing" (11,700 feet high), which were visited by Prjevalsk from the east during his last journey. Having succeeded in finding a pass to Tibet in the south of Nia, Colonel Pevtsoff proposes, as soon as the spring comes, to proceed himself by this pass to the table-land, while M. Roborovsky probably will be despatched to explore the same border-ridge further east, in the south of Tchertchen.

The pass

THE Boletin of the Madrid Geographical Society for the last quarter of 1889 contains a most valuable memoir by Dr. pine Islands. The author classifies the whole of the native popuFernando Blumentritt, on the intricate ethnology of the Philiplation in three broad divisions-Negrito, Malay, and Mongoloid; the last comprising those tribes which in their physical appearance betray certain Chinese or Japanese affinities. All are grouped in an admirably arranged alphabetical table, where their names, race, language, religion, culture, locality, and numbers are briefly specified in seven parallel columns.

With

a few variants and cross-references this table contains no less than 159 entries, and thus conveys in summary form all the essential particulars regarding every known tribe in the Philippine Archipelago. From it we gather that the Negritoes-that is, the true autochthonous element, variously known as Aetas, Atias, Atés, Etas, Itas, Mamánuas, &c., and physically belonging to the same stock as the Samangs of the Malay Peninsula

are now reduced to about 20,000, dispersed in small groups over the islands of Luzon, Mindoro, Tablas, Panay, Negros, Cebu, Paragan (Palawan), and Mindanao. A few also appear still to survive in Alabat, Busuanga, and Culioú. Of the Malay peoples by far the most numerous and important are the southern Bisayas (Visayas), and the northern Tagalas, both described as "civilized Christians," and numbering respectively 1,700,000 and 1,250,000. These two peoples are steadily encroaching on all the surrounding tribes, causing them to disappear by a gradual process of absorption or assimilation, and the time is approaching when the whole of the islands will be divided into two great nationalities bearing somewhat the same relation to each other that the High German does to the Low German branch of the Teutonic family.

SMOKELESS EXPLOSIVES.

I.

THE production of smoke which attends the ignition or ex

plosion of gunpowder is often a source of considerable inconvenience in connection with its application to naval or military purposes, its employment in mines, and its use by the sportsman, although occasions not unfrequently arise during naval and military operations when the shroud of smoke produced by musketry or artillery fire has proved of important advantage to one or other, or to both, of the belligerents during different periods of an engagement.

Until within the last few years, however, but little, if any, thought appears to have been given to the possibility of dispensing with or greatly diminishing the production of smoke in the appliction of fire-arms, excepting in connection with sport. The inconvenience and disappointment often resulting from the obscuring effects of a neighbouring gun-discharge, or of the first shot from a double-barrel arm, led the sportsman to look hopefully to gun-cotton, directly after its first production in 1846, as a probable source of greater comfort and brighter prospects in the pursuit of his pastime and in his strivings for success.

A comparison between the chemical changes attending the burning, explosion, or metamorphosis of gun-cotton and of gunpowder, serves to explain the cause of the production of smoke in the latter case, and the reason of smokelessness in the case of gun-cotton. Whilst the products of explosion of the latter consist exclusively of gases, and of water which assumes the transparent form of highly-heated vapour at the moment of its production, the explosive substances classed as gunpowder, and which consist of mixtures of saltpetre, or another nitrate of a metal, with charred wood or other carbonized vegetable matter, and with variable quantities of sulphur, furnish products, of which very large proportions are not gaseous, even at high temperatures. Upon the ignition of such a mixture, these products are in part deposited in the form of a fused residue, which constitutes the fouling in a fire-arm, and are in part distributed, in an extremely fine state of division, through the gases and vapours developed by the explosion, thus producing smoke.

In the case of gunpowder of ordinary composition, the solid products amount to over fifty per cent. by weight of the total products of explosion, and the dense white smoke which it produces consists partly of extremely finely-divided potassium carbonate, which is a component of the solid products, and, to a great extent, of potassium sulphate produced chiefly by the burning of one of the important solid products of explosionpotassium sulphide-when it is carried in a fine state of division into the air by the rush of gas.

With other explosives, which are also smoke-producing, the formation of the smoke is due to the fact that one or other of the products, although existing as vapour at the instant of its development, is immediately condensed to a cloud composed of minute liquid particles, or of vesicles, as in the case of mercury vapour liberated upon the explosion of mercuric fulminate, or of the aqueous vapour produced upon the ignition of a mixture of ammonium nitrate and charcoal, or ammonium nitrate and picric acid.

Until within the last half-dozen years, the varieties of gun. powder which have been applied to war purposes in this and other countries have exhibited comparatively few variations in chemical composition. The proportions of charcoal, saltpetre,

Friday Evening Discourse delivered by Sir Frederick Abel, F.R.S., at the Royal Institution of Great Britain, on January 31, 1890

and sulphur employed in their production exhibit slight difer ences in different countries, and these, as well as the characte of the charcoal used, its sources and method of produci underwent but little modification for very many years. Ti same remark applies to the nature of the successive operation pursued in the manufacture of black powder for artillery purpo in this and other countries.

The replacement of smooth-bore guns by rifled artillery which followed the Crimean war, and the increase in the size and powe of guns consequent upon the application of armour to ships ar! forts, soon called for the pursuit of investigations having for ther object the attainment of means for variously modifying the actvg of fired gunpowder, so as to render it suitable for the differen calibres of guns, whose full power could not be effectively, or m some instances safely, developed by the use of the kind of gen powder previously employed indiscriminately in artillery of al known calibres.

In order to control the violence of explosion of gunpowder, in modifying the rapidity of transmission of explosion from partic to particle, or through the mass of each individual particle, of which the charge of a gun is composed, the accomplishment of the desired results was, in the first instance, and indeed through out practical investigations extending over many years, sourn exclusively in modifications of the size and form of the individ masses composing a charge of powder, and of their density and hardness, it being considered that, as the proportions of saltpetre charcoal, and sulphur generally employed in the production of gunpowder very nearly correspond to those required for the development of the greatest chemical energy by those incorporate materials, it was advisable to seek for the attainment of 5 desired results by modifications of the physical and mechanial characters of, rather than by any modification in the proportions and chemical characters of, its ingredients.

The varieties of powder, which, as the outcome of card practical and scientific researches in this direction, have ba introduced into artillery service from time to time, and some of which, at any rate, have proved fairly efficient, have been of twe distinct types. The first of these, produced by breaking more or less highly-pressed cakes of black powder into grata pebbles, or boulders, of approximately uniform size and state the sharp edges and rough surfaces being afterwards removed in attrition (reeling and glazing), are simply a further developmen of one of the original forms of granulated or corned powder, represented by the old F. G., or small arms, and L G. = cannon powder. Gunpowder of this class, ranging in size about 1000 pieces to the ounce, to about six pieces to the have been introduced into artillery service, and certain of h viz. R. L. G. (rifle large grain), which was the first stry advance upon the old cannon-powder (L. G.); peblile-pi (P.), and large pebble or boulder-powder (P. 2), are employed more or less extensively in some guns of the pres day.

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The other type of powder has no representative among more ancient varieties; it has its origin in the obviously seal theoretical view that uniformity in the results furnisbat by: particular powder, when employed under like conditions, d mands not merely identity in regard to composition, but 20 identity in form, size, density, and structure of the individen masses composing the charge used in a gun. The practes realization of this view should obviously be attained, or at w rate approached, by submitting equal quantities of one and th same mixture of ingredients, presented in the form of powde uniform fineness and dryness, to a uniform pressure for a tr period in moulds of uniform size, and under surrounding ditions as nearly as possible alike. The fulfilment of the conditions would, moreover, have to be supplemented by equally uniform course of proceeding in the subsequent dive and other finishing processes to which the powder-masses wody be submitted.

The only form of powder, introduced into our artillery serv for a brief period, in the production of which these cond? were adhered to as closely as possible, was a so-called pelle powder, which consisted of smali cylinders having semt-perfor tions with the object of increasing the total inflaming surface the individual masses.

Practical experience with this powder, and with others p pared upon the same system, but with much less rigorous reg to uniformity in such details as state of division and condi of dryness of the powder before its compression into cylu fra or other forms, showed that uniformity in the ballistic proper

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