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of black powder could be as well and even more readily secured y the thorough blending or mixing together of batches presenung some variation in regard to density, hardness, or other atures, as by aiming at an approach to absolute uniformity in the characters of each individual mass composing a charge.

At the time that our attention was first actively given to this atect of the modification of the ballistic properties of powder, it had already been to some extent dealt with in the United States by Rodman and Doremus, and the latter was the first to rose the application, as charges for guns, of powder-masses roduced by the compression of coarsely grained powder into noulds of prismatic form. In Russia the first step was taken to ize the results arrived at by Doremus, and to adopt a prismatic wder for use in guns of large calibre. Side by side with the development and perfection of the nufacture of prismatic powder in Russia, Germany, and in das country, new experiments on the production of powdersses suitable, by their comparatively gradual action, for ployment in the very large charges required for the heavy Mery of the present day, by the powerful compression of & rates of more or less finely broken up powder-cake into es of greater size than those of the pebble, pellet, and powders, were actively pursued in Italy, and also by our wn Government Committee on Explosives, and the outcome of ry exhaustive practical investigations were the very efficient sano powder, or poudre progressif, of the Italians, and the alder and large cylindrical powders known as P2 and C2, Puced at Waltham Abbey, which scarcely vied, however, ch the Italian powder in the uniformity of their ballistic operties. Researches carried out by Captain Noble and the lecturer some years ago with a series of gunpowders differing considerably in position from each other, indicated that advantages might be sured in the production of powders for heavy guns by so moding the proportions of the constituents (e.g. by considerably arasing the proportion of charcoal and reducing the proportion phur) as to give rise to the production of a much greater me of gas, and at the same time to diminish the heat developed the explosion.

These researches served, among other purposes, to throw conerable light upon the cause of the wearing or erosive action of Jer-explosions upon the inner surface of the gun, which in may produce so serious a deterioration of the arm as to nish the velocity of projection considerably, and so affect the uracy of shooting, a deterioration which increases in extent n increasing ratio to the size of the guns, in consequence, eusly, of the large increase in the weight of the charges fired. Several causes undoubtedly combine to bring about the wearaway of the gun's bore, which is especially great where the lacts of explosion, while under the maximum pressure, can pe between the projectile and the bore of the gun. The Trat velocity with which the very highly heated gaseous and pid (fused solid) products of explosion sweep over the heated mace of the metal gives rise to a displacement of the particles posing it, which increases as the surface becomes roughened the first action upon the least compact portions of the metal, lhus opposes greater resistance; at the same time, the fect of the high temperature to which the surface is raised is reduce its rigidity and power of resisting the force of the ss torrent, and lastly some amount of chemical action on the metal, by certain of the highly heated non-gaseous roducts of explosion, contributes towards an increase in the

sive effects. A series of careful experiments made by ptain Noble with powders of different composition, and with her explosives, afforded decisive evidence that the material ich furnished the largest proportion of gaseous products, and hexplosion of which was attended by the development of the aliest amount of heat, exerted least erosive action.

It is probable that important changes in the composition of Towers manufactured by us for our heavy guns would have resailed from those researches, but in the meantime, two rament German gunpowder manufacturers had occupied themeves independently, and simultaneously, with the important tactical question of producing some more suitable powder for avy guns than the various new forms of ordinary black wder, the rate of burning of which, especially when confined a close chamber, was, after all, reduced only in a moderate igree by the increase in the size of the masses, and by such crease in their density as it was practicable to attain. The

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German experimenters directed their attention not merely to the proportions in which the powder ingredients are employed, but also to a modification in the character of charcoal, and the success attending their labours in these directions led to the practically simultaneous production, by Mr. Heidemann at the Westphalia Powder Works, and Mr. Düttenhofer at the Rottweil Works near Hamburg, of a prismatic powder of cocoabrown colour, consisting of saltpetre in somewhat higher proportion, of sulphur in much lower proportion, than in normal black powder, and of very slightly burned charcoal, similar in composition to the charcoal (charbon roux) which Violette, a French chemist, first produced in 1847 by the action of superheated steam upon wood or other vegetable matter, and which he proposed for employment in the manufacture of sporting powder. These brown prismatic powders (or Cocoapowders,' as they were termed from their colour), are distinguished from black powder not only by their appearance, but also by their very slow combustion in open air, by their comparatively gradual and long sustained action when used in guns, and by the simple character of their products of explosion as compared with those of black powder. As the oxidizing ingredient, saltpetre, is contained, in brown or cocoa powder, in larger proportion relatively to the oxidizable components, sulphur and charcoal, than in black powder, these become fully oxidized, while the products of explosion of the latter contain, on the other hand, larger proportions of unoxidized material, or only partially oxidized products. Moreover, there is produced upon the explosion of brown powder a relatively very large amount of water-vapour, not merely because the finished powder contains a larger proportion of water than black powder, but also because the very slightly charred wood or straw used in the brown powder is much richer in hydrogen than black charcoal, and therefore furnishes by its oxidation a considerable amount of water. The total volume of gas furnished by the brown powder (at o° C. and 760 mm. barometer) is only about 200 volumes per kilogramme of powder, against 278 volumes furnished by a normal sample of black powder, but the amount of water-vapour furnished upon its explosion is about three times that produced from black powder, and this would make the volume of gas and vapour developed by the two powders about equal if the heat of its explosion were the same in the two cases; the actual temperature produced by the explosion of brown powder, is, however, somewhat the higher of the two.

Although the smoke produced upon firing a charge of brown powder from a gun appears at first but little different in denseness to that of black powder, it certainly disperses much more rapidly, a difference which is probably due to the speedy absorption, by solution, of the finely divided potassium salts by the large proportion of water-vapour distributed throughout the socalled smoke.

This class of powder was substituted with considerable advantage for black powder in guns of comparatively large calibre; nevertheless it became desirable to attain even slower or more gradual action in the case of the very large charges required for guns of the heaviest calibres, such as those which propel shot of about 2000 pounds weight. Accordingly, the brown powder has been modified in regard to the proportions of its ingredients to suit these conditions, while, on the other hand, powder intermediate with respect to rapidity of action between black pebble powder and the brown powder, has been found more suitable than the former for use in guns of moderately large calibre.

than recent successful adaptation of machine guns and comparatively large quick-firing guns to naval service, more especially for the defence of ships against attack by torpedo boats, &c., has rendered the provision of a powder for use with them, which would produce comparatively little or no smoke, a matter of very considerable importance, inasmuch as the efficiency of such defence must be greatly diminished by the circumstance that, after a very brief use of the guns with black powder, the objects against which their fire is destined to operate, become more or less completely hidden from those directing them, by the dense veil of powder-smoke produced. Hence much attention has been directed during the last few years to the production of smokeless, or nearly smokeless powders for naval use in the above directions. At the same time, the views of many military authorities regarding the importance of dispensing with smoke in land engagements has also created a demand, the apparent urgency of which has been increased by various circumstances,

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SOLAR HALOS AND PARHELIA,

THE recent appearance of solar and lunar halos, pare! and paraselene, has called forth a considerable amou correspondence from all parts of the country, and the accomy a ing figure may be taken as a composite representation of solar phenomenon observed. A glance at the times at vi the halos were observed on the 29th ult., makes it apparent they occurred earliest in places of highest latitudes. At Draf in lat. 54°, the halo, with its attendant parhelia, was observ.! at 1.34 p.m., and the whole phenomenon disappeared u p.m.; at Burton-on-Trent, lat. 52° 48′, the halos and paris were first observed at 2 p.m., and lasted more or less distin until 3 p.m.; whilst about a degree south of this, at Oxf Colnbrook, and Walton-on-Thames, the phenomena p from about 3.30 to 4.30. The uniform difference in the n when the halos were observed at the places of different latita necessarily follows from the fact that they are formed by action upon solar rays of prismatic crystals of ice suspender in the air by the ascending currents which especially o the spring and autumn. Those prisms that are in such pout that the rays from the sun in transmission through them minimum deviation are the cause of the formation of halos, 4 since the angular distance of the sun equal to minimum devian is about 22°, this must be the radius of the halo, and the ternal circle, being produced by two such refractions in success has a radius of about 46°.

The properties of ammonium nitrate, of which the products of decomposition by heat are, in addition to water-vapour, entirely gaseous, have rendered it a tempting material to work upon in the hands of those who have striven to produce a smokeless powder, but its deliquescent character has been the chief obstacle to its application as a component of an explosive agent susceptible of substitution for black powder for service purposes. A German chemical engineer, F. Gaus, conceived that, by incorporating charcoal and saltpetre with a particular proportion of ammonium nitrate, he had produced an explosive material which did not partake of the hygroscopic character common to other ammonium-nitrate mixtures, and that, by its explosion, the potassium in the saltpetre formed a volatile combination with nitrogen and hydrogen, a potassium amide, so that, although containing nearly half its weight of potassium salt, it would furnish only volatile products. The views of Mr. Gaus regarding the changes which his so-called amide powder undergoes upon explosion were not borne out by existing chemical knowledge, while the powder compounded in accordance with his views proved to be by no means smokeless, and was certainly not nonhygroscopic. Mr. Heidemann has, however, been successful, by modifications of Gaus's prescription and by application of his own special experience in powder-manufacture, in producing an ammonium-nitrate powder possessed of remarkable ballistic properties, furnishing comparatively little smoke, which speedily disperses, and exhibiting the hygroscopic characteristics of ammonium-nitrate preparations in a decidedly less degree than any other hitherto prepared. The powder, while yielding a very much larger volume of gas and water-vapour than black or brown powder, is considerably slower than the latter; the charge required to produce equal ballistic results is less, while the chamber-pressure developed is lower, and the pressures along the chase of the gun are higher, than in the case of brown powder.

The halos recently observed do not differ in the main fra those frequently seen in higher latitudes, and consisting of a first circle or halo concentric with the sun, red within, v without, and at an angular distance of 22 or 23°; (2) a so03. circle or halo, similar to the preceding, but at an angular d

The ammonium-nitrate powder contains, in its normal, dried condition, more water than even brown powder; it does not exhibit any great tendency to absorb moisture from an ordinarily dry or even a somewhat moist atmosphere, but if the amount of atmospheric moisture approaches saturation, it will rapidly absorb water, and when once the process begins it continues rapidly, the powder-masses becoming speedily quite pasty. The charges for quick-firing guns are enclosed in metal cases, in which they are securely sealed up; the powder is therefore prevented from absorbing moisture from the external air, but it has been found that if the cartridges are kept for long periods in ships' magazines, in which, from their position relatively to the ships' boilers, the temperature is more or less elevated, sometimes for considerable periods, the expulsion of water from some portions of the powder masses composing the hermetically sealed charge, and its consequent irregular distribution, may give rise to want of uniformity in the action of the powder, and to the occasional development of high pressures. Although, therefore, this ammonium-nitrate powder may be regarded as the first successful advance towards the production of a comparatively smokeless artillery powder, it is not uniformly well adapted to the requirements which it should fulfil in naval service.

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a was seen at 3.35 p.m.; b at 3.45 p.m: cand dat sa p.mat fat 4.10 p.m.

tance of 46; (3) a portion of the parhelic circle appearing h zontal and diametral, and at the points of junction of this cr with the two halos, there is increased luminosity, which been taken for images of the sun; (4) horizontal ares, tanger to the circular halos, and a vertical line making a cross with horizontal portion of the parhelic circle.

Attention was first seriously directed to the subject of smokeless powder by the reports received about four years ago of remarkable results stated to have been obtained in France with such a powder for use with the magazine rifle (the Lebel) which was being adapted to military service. These reports were speedily followed by others, descriptive of marvellous velocities obtained with small charges of this powder, or some modifications of it, from guns of very great length. As in the case of mélinite, the fabulously destructive effects of which were much vaunted at about the same time, the secret of the precise nature of the smokeless powder was so well preserved by the French authorities, that surmises could only be made on the subject even by those most conversant with these matters. It is now well known, however, that more than one smokeless explosive has succeeded the original powder, the perfection of which was reported to be beyond dispute, and that the material now adopted for use in the Lebel rifle bears, at any rate, great similarity to preparations which have been made the subject of patents in this country, and which are still experimental powders in other countries.

(To be continued.)

Mr. John Lovell thus describes the phenomena observe Driffield: A splendid solar halo, with its attendant partie was observed this afternoon at 1.34 local time. The (diameter 45°) was almost perfect, the lower part only i slightly obliterated by the thick atmosphere near the hor Attached to the upper side, an inverted portion of a similar ha appeared, brilliantly illumined on the concave side, the low part giving out a dull red light. Again, 221" above this, also inverted, about 60° of arc beautifully coloured with r bow colours was clearly visible, the red side lowest. This a if it had been produced, would have circled the zenith. Tmock lights on each side of the halo were drawn out int cones of intensely bright light, while the inner sky of the was of a very dark shade. The most noteworthy feature of *~ display was a brilliant patch of pure white light in the po western sky, at a distance of 90° from the western mock and undoubtedly emanating from it, and which remained ve for nearly ten minutes. The whole phenomena disappearts 2.8 p.m., the sky then being covered with streaky cirro-sthaze from the north-north-west."

The patch of white light referred to by Mr. Lovell was do? · less produced by the junction of the parhelic circle with one the halos concentric with the sun. It is perhaps hardly sary to note the relation that exists between halos and un

stratus clouds, and that the space included within the halo is frequently of a more intense grey, or of a deeper blue than the rest of the sky.

The son of Sir W. Herschel observed the phenomena at tund, and noted :-"The sun was near the horizon. On ther side of it, at a distance of five or six diameters of the sun, 2, a mock sun. not very bright, of the colours of the rainbow, the one on the right being the brighter. There was a scarcely rceptible rainbow, of which red was the only colour visible, oning the two mock suns. This rainbow was brightest directly ver the sun. As far off again as the first was a second rainbow, , but fairly bright, which was equally visible from earth to th. Vertically above the sun, a third, a very bright rainbow, ched the second, being inverted, and having its centre straight ve head. It did not look quite as large as the second. The ather was clear, but the clouds on and above the horizon were a uniform grey colour, fading off gradually to a nearly clear overhead. There seemed always to be a much lighter shade grey in the clouds where the sun and the two mock suns

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The coloured parhelia observed indicates the refraction and ersion of solar light by vertical prisms, whilst the phenomena inverted arches are produced by the light which passes ngh horizontal crystals, at different azimuths.

Mr. Frank E. Lott, at Burton-on-Trent, observed a third helia on the part of the first halo vertically above the sun, #alst Mr. H. G. Williams, of Caterham, observing the phenomena about 4 p. m., noted that the sun appeared about 10° above the horizon. So far, the observations of two or three parhelia

two halos and two inverted arches agree with many former ptions. In the diagram appended, however, and in the ority of sketches received, the inverted arch is not given as tharc of a circle, but hyperbolic.

M. A. J. Butler, observing at Walton-on-Thames, remarks: The hyperbolic band above the sun was carefully noted ;" and Mr. C. A. Carus-Wilson, in the following observation made at tames, supports this view :

The sun was just setting behind a bank of hazy mist, appear" as a crimson disk enveloped in blue grey cloud; I first poticed a distinct bow, of light grey tint, and coloured for a ort distance at its left extremity with the ordinary rainbow -red inside. There then appeared a part of a second tw outside the other, coloured throughout the whole length ible-red inside. From the sun vertically upwards to the first , there was a band of white light, quite distinct from the the grey tint of the lower bow, and above the lower bow this and continued as a hyperbolic brush of white light: this brush ⚫ much brighter and better defined than the vertical band. A ty measurement, with a pocket sextant, of the angular radii of The two hows, gave 46 and 23° for the outside and inside bɔws reatively."

Mr. H. W. Pyddoke also remarks:-" The most noticeable ng of all was the shape of the upper bow, which was like a erhole except at its ends where it bent round again very dy" and other correspondents concur in this description the shape of the first inverted arch.

From the descriptions and figures given it is evident that the parhelia on the parhelic circle are the respective centres of hal similar to the first halo concentric with the real sun; the tersection of these two circles with that surrounding the sun the appearance of a hyperbolic curve at the top of it. An actly similar appearance was drawn by Pastorff as occurring on ecember 29, 1789, and is found in his "Beobachtungen der anenflecke"; and L'Astronomie for August 1889 contains a erywing and description of a very similar appearance.

Lunar halos followed the solar halos on the 29th ult., and n the following day Mr. G. B. Buckton, F.R.S., observed brenne parhelia and a halo at Haslemere, and describes hem as follows:

On

The sun shone brightly, but through a moderate haze. the night and on the left, at equal altitudes with the sun, an ong bright patch of light appeared. That on the left was the ghtest, and formed a blurred image of the sun with all the omatic colours of the rainbow, but the colours were reversed order. The upper and lower parts of these mock suns were trawn out, and formed portions of a large circle of about (by eye estimate 20 radius. These images were connected with the haze, but a lower stratum of finely striated cloud came between the eye and these patches. Immediately above the true sun a third patch of light occurred, through which a portion of an in

verted circle was seen, the greater part of which was lost in the blue of the sky above. The right-hand mock sun was fainter than the other, on account of the grey haze being more dense." Mr. Buckton's observation is a demonstration of the principle laid down-namely, that parhelia always appear at the same elevation as the true sun, and are united to each other by a white horizontal circle, whose pole is the zenith. This circle changes in elevation with the true sun; and the apparent semidiameter is always equal to the distance of the luminary from the zenith.

Mr. Nagel, of Trinity College, Oxford, notes that :-"The solar halos on the afternoon of January 29 were very clearly seen in Oxford; the tangential arc to the outer halo was extremely brilliant, and the two mock suns at the extremities of the horizontal diameter of the inner halo were well marked. During part of the time the halos lasted, a whitish incomplete circle was seen about 80° from the sun, and consequently beyond the zenith. This circle seemed to correspond to that first described by Helvelius in 1661."

It is evident from the descriptions given that the parhelia are not, as is sometimes supposed, images of the real sun at all, but only the junctions of two of the circles formed. The upper and the lower parts of these mock suns were drawn out and connected with the first halo, whilst their sides were observed to be drawn out and to merge into the parhelic circle.

THE INSTITUTION OF MECHANICAL
ENGINEERS.

THE forty-third annual general meeting of the Institution
of Mechanical Engineers took place on January 29, 30,
and 31, in the theatre of the Institution of Civil Engineers.
The papers down for reading and discussion were as follows:
on the compounding of locomotives burning petroleum refuse in
Russia, by Mr. Thomas Urquhart, Locomotive Superintendent,
Grazi and Tsaritsin Railway, South-East Russia; on the burning
of colonial coal in the locomotives on the Cape Government
railways, by Mr. Michael Stephens, Locomotive Superin-
tendent; and on the mechanical appliances employed in the
manufacture and storage of oxygen, by Mr. Kenneth S. Murray,
of London. The latter paper was communicated through Mr.
Henry Chapman.

Mr. Urquhart's paper is one of a series of excellent and thoroughly useful descriptions of work done by that gentleman on his railway, and had been for some time promised to the Institution. In order to satisfy himself as to the utility and saving of fuel in compound locomotives, he obtained the sanction of the Government for altering one locomotive by way of experiment. The altered engine was put to work, and the driver was allowed over a month's running to get fully acquainted with the handling in regular service. Comparative trials were then made of the compound against a non-compound locomotive with the same weight of train, on the same days, so as to expose them both to the same circumstances in regard to weather. It was clearly proved that the compound burnt 22 per cent. less of the petroleum refuse used as fuel than the non-compound engine, and the author's experience has left no doubt in his own mind that compound locomotives are the engines of the future in all countries. Mr. Urquhart's results are thoroughly borne out by those obtained in this country by Messrs. Worsdell and Webb. Some engi neers suppose that this great economy in fuel is due to the higher working steam pressure, and therefore greater expansion in the compound engines as compared with the non-compound engines.

The paper by Mr. Michael Stephens is a description of the South African coal-fields, their discovery, and general working within the last sixteen years. It appears from the paper that the local coal cannot be burned to advantage without a special arrangement of fire-bars-as may be well imagined, since it contains nearly 30 per cent. of incombustible matter.

Mr. Kenneth S. Murray gives an interesting account of the commercial preparation of oxygen from the atmosphere by means of the alternate heating and cooling of the monoxide of barium. About thirty years ago the eminent French chemist Boussingault made the discovery that, at a temperature of about 1000° F., the monoxide of barium would absorb oxygen readily from the atmosphere, with the resulting formation of the dioxide;

and that at a higher temperature of about 1700° F. the oxygen thus absorbed would be given off again, and the monoxide would apparently be restored to its original condition. The paper clearly describes the machinery required for the manufacture of oxygen by means of barium oxide.

UNIVERSITY AND EDUCATIONAL

INTELLIGENCE.

OXFORD.-The lecture lists for this term include the following courses :-Prof. Clifton, Magnetism; Mr. Baynes, Thermodynamics; Prof. Odling, Diacidic Olefine Acids; Mr. Veley, Physical Chemistry. Prof. Burdon-Sanderson has resumed his lectures, and Mr. Gotch is treating of the Physiology of Muscle. Dr. Tylor lectures on the Development of Religions.

An open Fellowship in Mathematics at Christ Church has been awarded to Mr. C. H. Thompson, Queen's College, Lecturer in Mathematics at Lampeter. No other mathematical Fellowship has been awarded for about seven years.

The arrangement of the Pitt-Rivers anthropological collection at the Museum is proceeding as rapidly as the constant acquisition of new material allows, and a large portion of the collection is now open for public inspection.

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the thirteen races which he proposes for his classification, addr separate remarks on the varieties of each.-The dog, by M. de Mortillet. Assuming from negative evidence the existence of the dog in the Quaternary age, the author traces! presence onwards from the Kjøkkenmoddings, in wh abundant remains of this animal are to be found. Passing the prehistoric ages in Europe he considers at length the evithat can be advanced of the existence of several varieties of t dog among the Egyptians, and later on among the acc Greeks and Romans; and in the fact of the innumenti varieties of Canis domesticus, M. de Mortillet believes we en one of the most conclusive proofs of evolution.-Observat.** on the skeletons of two young orangs, by M. Herve.-~ Columbian ethnography of Venezuela, by Dr. Marcato. T most interesting report in this treatise is that referring to t Grotto de Cerro de Luna, owing to the almost absolute ceri that it had never been entered since Guiana was first visiter white men. Here Dr. Marcano recovered fifty two male, c forty-three female skulls, with five of children, together wi numerous long bones. Among these skulls many were pr red, and others had obviously been embalmed. The gene mean of their cephalic index was 79, while the fac characters were mesorrhinic and prognathic.-On corrent-variations in the biceps, by M. G. Hervé.-A report of “ Seventh Conference on Transformism, by M. M. Duval. author here gives an interesting biographical notice of the grea French savant Lamarck, entering at the same time fully the character and scope of his researches, and showing how far his views differed from, or approximated to, those of Dar As a résumé of what Lamarck attempted on the same lines

(3) S. F. Harmer (King's), on the origin of the embryos in inquiry so successfully followed by Darwin, M. Duval's reput the ovicells of Cyclostomatous Polyzoa.

Prof. Stuart has communicated to the Vice-Chancellor his intention of resigning the Chair of Mechanism and Applied Science before the end of the current academical year.

SCIENTIFIC SERIALS.

American Journal of Mathematics, vol. xii., No. 2 (Baltimore, January 1890).—The number opens with the concluding part of Mr. Forsyth's paper on "Systems of Ternariants that are Algebraically Complete" (pp. 115-160). It is illustrated with numerous tables and closed with a useful abstract of contents. In the following memoir (pp. 161–190), by Prof. Franklin, on "Some Applications of Circular Co-ordinates," the author investigates, with the aid of these co-ordinates, some interesting theorems relating to the orientation of systems of lines given in a recent volume (vol. x. p. 258) by M. Humbert. Several further illustrations are given, and the memoir closes with a discussion of the curve given by the equation sin xdx = sin ydy.Mr. F. N. Cole writes (pp. 191-212) on "Rotations in Space of Four Dimensions." The present article is preliminary to a second paper on groups of rotations in four-dimensional space which is to follow.

Bulletins de la Société d'Anthropologie, tome xii., série iii., fasc. 3 (Paris, 1889).-Continuation of M. Dumont's paper on the natality of Paimpol, in which he treats at great length of the causes which influence the ratio of marriages contracted in every hundred of the population in the maritime districts of Brittany, and of the number of children born in each family. In both these respects the means rank amongst the lowest for all France. One cause for this may be the preponderance of women over men, a large number of the latter being engaged as seamen, or taking part in the Iceland and other distant fisheries. Another factor in this problem is probably the subdivision of property among all the members of a family, who in the peasant and small burgher classes, not uncommonly remain together all their lives, and avoid marriage in the fear of diminishing their individual shares of the patrimony. This, coupled with the repugnance, so common among the French peasantry, against large families, leads indirectly to late marriages or to celibacy, and has thus exercised a baneful influence on the normal increase of the population. An essay on the classification of human races, based entirely on physical characters, by M. Denniker. Believing in the long persistence of types in spite of the constant intermixture of races, the author thinks that it is only by a careful study of the typical characteristics in a so-called ethnic group that we can arrive at any correct idea of the affinities between different races. In an elaborate synoptical table he enumerates

presents much interest for the English reader.-On the mesh of Morbihan, by M. Gaillard.-On the discovery of Re hausian flint implements near Macon, by M. Lafay.-Compen son of three sub-species of man, by M. Lombard.

SOCIETIES AND ACADEMIES.
LONDON.

Royal Society, January 23.-"On a Photographic Meth for determining Variability in Stars." By Isaac Ruberti F.R.A.S. Communicated by Prof. J. Norman Locky F.R.S.

Some of the uncertainties which necessarily attend the termination of variability in the brightness of stars by er observations are removed by the application of photogra methods, and particularly by that of giving two or more es posures of the same photographic plate to a given sky space. with intervals of days or weeks between each exposure.

In this way any errors caused by atmospheric, actinic chemical changes, together with those due to personal bias, eliminated, and the study of stellar variability can be pur under conditions that admit of the necessary exactitude.

As an illustration of the applicability of this dual photograph method, the enlargement on paper from the negative is n submitted. It shows the results obtained by two exposure the same plate to the sky in the region of the great nebula Orion. The first exposure was of two hours' duration January 29, and the second of two and a half hours February 3, 1889. The stellar images formed during 1two exposures are 00122 of an inch apart, measured from eat to centre, and therefore comparable with each other in the ho of a microscope. When the images are examined in manner thus indicated, and their diameters also measure! means of a suitably made eye-piece micrometer, it is found at least ten of the photographed stars, the magnitudes of wher are estimated to range between the 7th and 15th, have chang to a considerable extent in the short interval of five days. The ten stars referred to are to be found within an area of 1. ↑ than two square degrees of the sky, and in the table given the co-ordinates of their positions with reference to § Onva The measurements of the diameters of their photo images & scale of 0'00002 of an inch are also given.

"Physical Properties of Nickel Steel." By J. Hopkin D.Sc., F. R.S.

Mr. Riley, of the Steel Company of Scotland, hu ki sent me samples of wire drawn from the material concerning magnetic properties of which I recently made a communica! **

the Royal Society. As already stated, this material contains 5 per cent. of nickel and about 74 per cent. of iron, and over range of temperature from something below freezing to 580° C. I can exist in two states, magnetic and non-magnetic. The wire as sent to me was magnetizable as tested by means / a magnet in the ordinary way. On heating it to a dull red, it became non-magnetizable, whether it was cooled slowly exceedingly rapidly by plunging it into water. A quantity the wire was brought into the non-magnetizable state by aling it, and allowing it to cool. The electric resistance of a sertion of this wire, about 5 metres in length, was ascertained terms of the temperature; it was first of all tried at the dinary temperature, and at temperatures up to 340° C. The pecific resistances at these temperatures are indicated in the arve by the numbers 1, 2, 3. The wire was then cooled by Leans of solid carbonic acid; the supposed course of change of tance is indicated by the dotted line on the curve; the actual nervations of resistance, however, are indicated by the crosses a the neighbourhood of the letter A on the curve. The wire

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was then allowed to return to the temperature of the room, and was subsequently heated, the actual observations being shown by crosses on the lower branch of the curve; the heating was continued to a temperature of 680° C., and the metal was then allowed to cool, the actual observations being still shown by crosses. From this curve, it will be seen that in the two states of the metal, magnetizable and non-magnetizable, the resistances at ordinary temperatures are quite different. The specific resistance in the magnetizable condition is about 0'000052, in the non-magnetizable condition it is about o'000072. The curve of resistance in terms of the temperature of the material in the magnetizable condition has a close resemblance to that of soft iron, excepting that the coefficient of variation is much smaller, as, indeed, one would expect it to be in the case of an alloy; at 20° C. the coefficient is about o'00132, just below 600° C. it is about 00040, and above 600° it has fallen to a value less than that which it had at 20° C. The change in electrical resistance effected by cooling is almost as remarkable as the change in the magnetic properties.

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amples of the wire were next tested in Prof. Kennedy's oratory for mechanical strength. Five samples of the wire were taken which had been heated and were in the non-magserable state, and five which had been cooled and were in the gnetizable state. There was a marked difference in the andness of these two samples; the non-magnetizable was exemely soft, and the magnetizable tolerably hard. Of the five nonagnetizable samples the highest breaking stress was 50'52 tons ser equare inch, the low e-t 48 75; the greatest extension was 33'3 er cent., the lowest 30 per cent. Of the magnetizable samples, e highest breaking stress was 88-12 tons per square inch, the We was 85.76; the highest extension was 8.33, the lowest 70. The broken fragments, both of the wire which had ongmally been magnetizable and that which had been nongnetizable, were now found to be magnetizable. If this maerial could be produced at a lower cost, these facts would hase a very important bearing. As a mild steel the non-magsetizable material is very fine, having so high a breaking stress for so great an elongation at rupture. Suppose it were used for any purpose for which a mild steel is suitable on account of this considerable elongation at rupture, if exposed to a sharp frost Js properties would be completely changed-it would become essentially a hard steel, and it would remain a hard steel until t had been heated to a temperature of about 600° C.

Geological Society, January 22.-W. T. Blanford, F.R.S., President, in the chair.-The following communication was d-On the crystalline schists and their relation to the Mesorocks in the Lepontine Alps, by Prof. T. G. Bonney, R.S. In the debate upon the paper on two traverses of the crystalline rocks of the Alps (read December 5, 1888) it was led that rocks had been asserted on good authority to exist in be Lepontine Alps, which contained Mesozoic fossils, together wah gamets, staurolites, &c., and thus were undistinguishable from crystalline schists regarded by the author as belonging to the presumably Archæan massifs of that mountain-chain. In reply the author stated that he regarded this as a challenge to demonstrate the soundness or unsoundness of the hypothesis to shich he had committed himself. The present paper gives the result of his investigations, undertaken in the month of July See Address to the Institution of Electrical Engineers (NATURE, January

1889, in company with Mr. James Eccles, to whom the author is deeply indebted for invaluable help. The paper deals with the following subjects :-(1) The Andermatt Section. By the geologists aforesaid, a highly crystalline white marble which occurs on the northern side of the Urserenthal trough, at and above Altkirch, near Andermatt, is referred to the Jurassic series (members of which undoubtedly occur at no great distance, almost on the same line of strike). The author describes the relation of the marble to an adjacent black schistose slate, and discusses the significance of some markings in the former which might readily be considered as organic, but to which he assigns a different origin. He shows that there are most serious difficulties in regarding these two rocks as members of the same series, and explains the apparent sequence as the result of a sharp and probably broken infold, as in the case of the admitted band of Carboniferous rock at Andermatt itself. That the section is a difficult one on any hypothesis the author admits, but in regard to the former of these, after a discussion of the evidence, he concludes, "that tendered on the spot demands a verdict of 'not proven-that obtainable in other parts of the Alps, will compel us to add, 'not provable.' (2) The Schists of the Val Piora. These schists, already noticed by the author in his Presidential address to the Society in 1886, occur in force near the Lago di Ritom, and consist of two groups-the one dark mica-schists,s ometimes containing conspicuous black garnets, banded with quartzites, the other various calc-mica schists; between them, apparently not very persistent, occurs a schist containing rather large staurolites or kyanites. On the north side is a prolongation of the garnet-actinolite (Tremola-) schists of the St. Gothard and then gneiss, on the south side gneiss. There is also some rauchwacké. This rock, at first sight, appears to underlie the Piora schists, and thus to be the lowest member of a trough. If so, as it is admittedly about Triassic in age, the Piora schists. would be Mesozoic. The author shows that (1) the latter rocks do not form a simple fold; (2) they are, beyond all question, altered sediments; (3) they have often been greatly crushed subsequent to mineralization; (4) the garnets, staurolites, &c. (if not injured by subsequent crushing) are well developed and characteristic, and are authigenous minerals. (3) The Rauchwacké and its Relation to the Schist. (a) The Val Piora Sections: The author shows that the rauchwacké, which

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