structore, doubly refractive power, and, in fact, is optically tentate like the inclosed silicate. It appears to be produced y some agent acting from without, perhaps heat in conjunction with a reducing gas. The agent has not caused friction, but a ght modification of the texture of the surface.

Indications afforded by Crystalline Structure.

1

The mixed minerals of meteorites have been subjected to topic examination by Sorby and Rose, and both have Eind that the crystals differ in some essential particulars from hose of volcanic rocks.

Sorby long since showed that when crystals are formed by deposition from water or from a mass of melted rock, they often ch up portions of this water or melted stone which can be en 28 cavities containing fluid or glass, Crystalline minerals ime! by purely aqueous or by purely igneous processes thus be distinguisher. One of the most common of the minerals in meteorites is olivine, and when met with in volcanic as this mineral usually contains only a few and small glassvities in comparison with those seen in such minerals as augite. The crystals in meteorites are generally only small, and thus te dithculty of the question is considerably increased. However, bs careful examination with high magnifying power, Sorby and well-marked glass-cavities, with perfectly fixed bubbles, inclosed glass being sometimes of brown colour and having ted crystals. On the contrary he was never able to detect ny trace of fluid-cavities, with moving bubbles, and therefore he Ads it very probable, if not absolutely certain, that the crysalline minerals in meteorites were chiefly formed by an igneous ts, like that which has produced lava, and analogous ⚫anic rocks.

Passing from the structure of the individual crystals to that of se aggregate, Sorby points out that in some cases we have a ructure in every respect analogous to that of erupted lavas, ugh even then there are very curious differences in detail. The results of the observations of the kinds of crystallization ted in meteorites by many eminent authorities go to show that took place hastily. Thus Brezina, after making a complete ay of the Vienna collection, comes to the conclusion that ructural features of meteorites are the result of a hasty allization.

Again, it is the opinion of several high authorities that the rystallization did not necessarily take place under conditions of gh temperature.

M Daubrée's opinion is thus expressed :-3

"It is extremely remarkable that, in spite of their great ndency to a perfectly distinct crystallization, the silicate comanations which make up the meteorites are there only in the ortion of very small crystals, all jumbled together as if they 2 not passed through fusion. If we may look about us for Tebing analogous, we should say that, instead of calling to and the long needles of ice which liquid water forms as it rs, the fine-grained texture of meteorites resembles rather of hoar frost, and that of snow, which is due, as is known, to he immediate passage of the atmospheric vapour of water into

Te solid state."

This possibility of the absence of high temperature is thus arver insisted upon by Prof. Newton :

"The meteorites resemble the lavas and slags of the earth. These are formed in the absence of water, and with a limited aply of oxygen, and heat is present in the process. But is Test necessary? Some crystallizations do take place in the cold; the are direct changes from gaseous to solid forms. We cannot in the laboratory reproduce all the conditions of crystallization the cold of space. We cannot easily determine whether the fe absence of oxygen will not account fully for the slag-like aracter of the meteoric minerals. Wherever crystallization can place at all, if there is present silicon and magnesium and un ani nickel, with a limited supply of oxygen, their silicates ght to be expected in abundance, and the iron and nickel in eir metallic forms. Except for the heat, the process should be talogoas to that of the reduction of iron in the Bessemer cupola, When the limited supply of oxygen combines with the carbon, nd leaves the iron free."

Should this view be subsequently confirmed, all early ideas ching the formation of meteorites will require to be modified. us, in 1855. Prof. Lawrence Smith stated: "They have all een subject to a more or less prolonged igneous action correProc. R.S.. January 1964.

Quoted by Newis, NATURE, vol. xxxiv. p. 535.

sponding to that of terrestrial volcanoes." Haidinger, in 1861, not only declared for high temperature, but for high pressure. Obviously, these views, which were based more upon the analogues of some of the meteoriteswith volcanic basic rocks than upon the actual character of the crystallization, suggested the formation of large masses; and the ideas that comets were solid bodies and that meteorites were fragments of comets or planets were both based upon these views, and the higher the temperature required and the slower the crystallization, the larger in imagination did these possible birthplaces of the meteorites become.

If neither much time nor heat be required to produce the crystallization observed, then, with Prof. Newton, we can suppose "a mass containing silicon, magnesium, iron, nickel, a limited supply of oxygen, and small quantities of other elements, all in their primordial or nebulous state (whatever that may be), segregated somewhere in the cold of space. As the materials consolidate and crystallize, the oxygen is appropriated by the silicon and magnesium, and the iron and nickel are deposited in metallic form. Possibly the heat developed may, before it is radiated into space, modify and transform the substance. The final result is a rocky mass (or possibly several adjacent masses) which sooner or later is, no doubt, cooled down throughout to the temperature of space.'

We shall see subsequently that there are many known causes in operation which will provide us with just such a mixed massof vapours as Prof. Newton requires, and it is at once obvious that, not only is the generic separation into iron and stones thus accounted for, but the special form of crystallization observed in stones and the special chondritic structure observed both in irons and stones would all arise from the same cause. Evidences of Heating and Action of Violent Forces at Different

Times.

The peculiarities in the mineralogical structure of the meteorites are probably in part due to the successive heatings and coolings to which they were subjected with each approach of the comet to the sun, and partly, perhaps, to the heat of combination of oxygen and silicon. They were most probably formed in a limited supply of oxygen, so that the elements possessing greatest affinity for that element were the first to form compounds, leaving iron and nickel in the metallic or uncombined state.

Some meteoric stones from examination seem to have been heated to a high temperature right through their mass. Such cases as Orvinio, Chantonnay, Juvenas, and Weston show signs that fragments are cemented together with a material of the same substance as themselves. Again we have indications of chemical changes, the chondroi in some stones being found to be surrounded by spherical and concentric aggregations of minute particles of nickel, due, as is supposed, to the reducing action of hydrogen at a high temperature.

Some meteorites are merely breccias, consisting of fragments, the débris of pre-existing meteorites, or of the original mass tremendously shattered, and subsequently cemented together. In this connection Sorby writes:

"It would therefore appear that, after the material of the meteorites was melted, a considerable portion was broken up into small fragments, subsequently collected together, and more or less consolidated by mechanical and chemical actions, amongst which must be classed a segregation of iron, either in the metallic state or in combination with other substances. Apparently this breaking up occurred in some cases when the melted matter had become crystalline, but in others the forms of the particles lead me to conclude that it was broken up into detached globules whilst still melted (Mezo-Madaras, Parnellee). This seems to have been the origin of some of the round grains met with in meteorites; for they occasionally still contain a considerable amount of glass, and the crystals which have been formed in it are arranged in groups, radiating from one or more points on the external surface, in such a manner as to indicate that they were developed after the fragments had acquired their present spheroidal shape (Aussun, &c.). In this they differ most characteristically from the general type of concretionary globules found in terrestrial rocks, in which they radiate from the centre; the only case that I know at all analogous being that of certain Oolitic grains in the Kelloways rock at Scarborough, which have undergone a secondary crystallization." 2

Mr. Sorby remarks: "A most careful study of their microscopical structure leads me to conclude that their conSee Newton, NATURE, vol. xxxiv. p. 534.

Berlin Acad. Trans. 4 NATURE, loc. cit.

stituents were originally at such a high temperature that they were in a state of vapour, like that in which many now occur in the atmosphere of the sun, as proved by the black lines in the solar spectrum." We may, in fact, look upon them as being to planets what the minute drops of water in the clouds are to an ocean. He has shown that possibly, after the condensation of the vapour, they collected into larger masses, which have been subsequently changed by metamorphic action, broken up by mutual impact, and again collected and solidified, the meteoric irons possibly being those portions of the metallic constituents which were separated from the rest by fusion when the metamorphosis was carried to the extreme point.

In this manner the subsequent heating, or any number of subsequent heatings, are explained.

Iron Meteorites not fused in falling.1

A question of no slight interest in regard to the changes which meteoric irons undergo during their passage through the atmosphere is whether their surface becomes fused. From his study of the Charlotte meteorite, Dr. Smith is inclined to answer it in the negative. The fact of the delicate reticulated surface having been preserved is a proof that the heat, instead of having been raised to a high temperature, has quickly been conducted away into the mass of metal. Had fusion of the superficial layer taken place, the meteorite would have been coated with molten oxide.

Veins.

Now and again we come across meteorites which have veins, like terrestrial rock-veins, running right through them. Prof. Maskelyne's description of them is as follows:-2

66

Just as in a mine one may meet with a fissure that, once dividing the country,' but subsequently filled by rocky

matter, cuts across the course of a mineral vein which itself was originally formed in a similar way; and just as such a cross fissure, thus intersecting with the original metalliferous vein, often gives us evidence of a heave, i.e. that one side of the new fissure has slid upwards or downwards along the other, so an exactly similar thing is met with in meteorites, and is admirably seen in the microscopic sections of them."

Faults and throws are both represented in meteorites. In that of Aumières there is a throw of several centimetres in licated, and faults intersect. These faults are accompanied by heat due to the friction of the surfaces, and in the case of gray stony meteorites the faults are black like the crust.3 (The black veins are physically connected with the crust, and are supposed to have the same origin, the melted material having filled up the fissures.)

On examining such meteorites as Château-Renard, Pultusk, and Alessandria, it is found that some of the spherules even are broken in half and the halves separated from each other by a vein of meteoric iron or troilite, and in some cases by a black fused substance, like the crust of a meteorite.

The Presence of Sulphides.

The presence of sulphides, which must have been formed when both water and free oxygen were absent, shows a distinctly nonterrestrial condition, as, indeed, does also the presence of small particles of iron. On this point Dr. Flight remarks: "If the conditions necessary for the formation of pure calcium sulphide be borne in mind, the evidence imported into this inquiry by the Bustee aerolite seems further to point to the presence of a reducing agent during the formation of its constituent materials.”

Sorby's General Conclusions.

We have before referred to Sorby's microscopical examination of meteorites. In 1865 he stated the general conclusions he had arrived at as follows. It will be seen how remarkable the agreement is between him and Reichenbach.

"As shown in my paper in the Proceedings of the Royal Society (xii. 333), there is good proof of the material of meteorites having been to some extent fused, and in the state of minute detached particles. I had also met with facts which seemed to show that some portions had condensed from a state of vapour; and expected that it would be requisite to adopt a modified nebular hypothesis, but hesitated until I had obtained more satisfactory evidence. The character of the constituent 'Quoted from the "Report on Observations of Luminous Meteors during the year 1874-75," p. 247. 2 NATURE, vol xii. p. 505.

3 Flight, loc. cit., p. 111.

4 Loc. cit., p. 119.

particles of meteorites and their general microscopical struct.** differ so much from what is seen in terrestrial volcanic rocks, the it appears to me extremely improbable that they were ever tions of the moon, or of a planet, which differed from a b meteorite in having been the seat of a more or less moti volcanic action. A most careful study of their microsc structure leads me to conclude that their constituents wr originally at such a high temperature that they were in a state vapour, like that in which many now occur in the atmosphere the sun, as proved by the black lines in the solar spectrum. cooling, this vapour condensed into a sort of cometary formed of small crystals and minute drops of melted stony matte which afterwards became more or less devitrified and crystaler This cloud was in a state of great commotion, and the partic moving with great velocity were often broken by collin After collecting together to form larger masses, heat, genere by mutual impact, or that existing in other parts of space the which they moved, gave rise to a variable amount of m morphism. In some few cases, when the whole mass was fur all evidence of a previous history has been obliterated; and on solidification a structure has been produced quite similar to of terrestrial volcanic rocks. Such metamorphosed or ftmasses were sometimes more or less completely broken up violent collision, and the fragments again collected together a solidified. Whilst these changes were taking place, varmetallic compounds of iron were so introduced as to indicate th they still existed in free space in the state of vapour, and cdensed amongst the previously formed particles of the meteor At all events the relative amount of the metallic consutus. appears to have increased with the lapse of time, and they crystallized under conditions differing entirely from those whi occurred when mixed metallic and stony materials were morphosed, or solidified from a state of igneous fusion in small masses that the force of gravitation was too weak separate the constituents, although they differ so much in sie. gravity. (Report of British Association, 1864) Possibly, hors ever, some meteoric irons have been produced in this ma by the occurrence of such a separation. The hydro carbons which some few meteorites are impregnated may have conder from a state of vapour at a relatively late period.

"I therefore conclude provisionally that meteorites are ter ́s a of the existence in planetary space of physical conditions m or less similar to those now confined to the immediate ne bourhood of the sun, at a period indefinitely more remote that of the occurrence of any of the facts revealed to us by study of geology-at a period which might in fact be c pre-terrestrial."

Are Meteorites merely Modern Phenomena ?

It has often been a subject of remark that in spite of the Y** considerable number of undoubted meteorites now in var collections, we scarcely have traces of any which suggest falls in any of the geological periods preceding the presente The iron found by Prof. Nordenskiold at Ovifac, Wer Greenland, was at first thought to be meteoric iron of Mi age, but after an analysis of the basalt or lava rocks of Al Disco Island, a part of the same basaltic range in Greenland, 100 miles from the spot where Prof. Nordenskiold's discovery made, it was held by most authorities to be no other than metallic nickel-iron which is, though extremely rarely, a o product in some terrestrial rocks. Other explorers besides FNordenskiöld have brought back specimens of this iron, Dr. Lawrence Smith has stated, not only that the nickel-irus Ovifac is without doubt of terrestrial origin, but that the specime brought back by the other explorers resembles the Orif: each other remarkably, while they differ from meteoric in the large proportion of combined carbon in their compositio Again, in NATURE, vol. xxxv. p. 36, we have a description another meteorite supposed to be a fossil one, found in a b of Tertiary coal. It was said to belong to the group of meti irons, and was taken from a block of coal about to be used it manufactory of Lower Austria. On its examination by v specialists, different origins were assigned to it. Some belie it to be meteoric, others an artificial production, and the again thought it was a meteorite modified by the hand of mu After a careful examination Dr. Gurlt came to the conclu that there was no ground for believing in the intervention The mass was almost a cube, two opposite la being rounded, and the four others being made smaller by roundings. A deep incision ran all through the cube.

human agency.

A

tices and the incision bore such characteristic traces of meteoric n as to show that the mass was not the work of man. Tyer of oxide formed a thin covering of the iron; it was 67 mm. 5th 67 mm. broad, and 47 mm. at its thickest part; it was Cound to be about as hard as steel, and besides carbon it conaned a small percentage of nickel. It resembled the meteoric asses of St. Catherine in Brazil, and Braunau in Bohemia, find in 1847.

I be evidence, however, is so strong that what we really obtain tow at the earth's surface forms but a very small portion of the arteorites which enter the upper air, that it would not be able that in former ages of the earth's history, when the sphere was denser than it is now, anything whatever would eft by the time the surface was reached.

J. NORMAN LOCKYER.

SCIENTIFIC SERIALS.

American Journal of Science, January.-Measurement of the Pravian arc, by E. D. Preston. In this paper, which was - before the American Association for the Advancement of Seter at Toronto, August 1889, the author reviews the whole tion of the relative lengths of the earth's axes, dealing in with Bouguer's expedition to Peru in 1735, and arguing as the amplitude of bis Peruvian arc may be in error by many unds. Hence he contends that the geodetic science of to-day uds the remeasurement of this arc.-Neutralization of action, by John Trowbridge and Samuel Sheldon. A system tralization for inductive disturbances is here described, sch might be adopted where it is impossible to employ entire allic cireants in which the earth plays no part.-Divergent lation and the Darwinian theory, by Rev. John T. Gulick. The author discusses Darwin's apparently contradictory views the causes of natural selection on the one hand, and on the er on the causes of diversity of natural selection. He conthat, though Darwin has not recognized segregation as a cessary condition of divergence of species, he has indicated Srocess (geographical or local separation under different ronments) by which segregation is produced in nature, Ging, however, that this is not the only cause of segregation * consequent divergence.-The Devonian system of North Sath Devonshire, by H. S. Williams. During a recent to England the author studied this system both on the spot in the geological collections in London and elsewhere. He fels especially, (1) on the close resemblance of the English Levonian species to those of the New York Devonian, though ly passing under different names, and (2) on the character the North and South Devonian rocks, which in appearance, position, and order are as different as two distinct systems can be. --The zinciferous clays of South-West Missouri, theory as to the growth of the calamine of that section, WH. Seamon. Full analyses are given of the so-called "allow" and "joint" clays occurring associated and sometimes erited in every calamine digging in South-West Missouri. Leve analyses show a large percentage, often from 50 to of zinc oxide, and it is inferred that at one time all massive calamine probably existed in "tallow clays" preated from solutions.-On the spectrum of Ursa Majoris, Howard C. Pickering -Origin of normal faults, by T. leilard Reade Some critical remarks are offered on Prof. Inte's recent explanation of the origin of normal faults,

not new, and presents many insuperable difficul--Papers were submitted by J. Dawson Hawkins, on a ecimen of minium from Leadville; by William P. Blake, on me minerals from Arizona; by F. A. Genth, on a new ocrence of corundum in Patrick County, Virginia; by Alfred Lane, on the estimation of the optical angle of observations parallel light by L. G. Eakins, on a new stone meteorite Texas; by Edward S. Dana, on the barium sulphate from Terkin's Mill, Templeton, Province of Quebec; and by O. C. Marsh, on some new Dinosaurian reptiles recently discovered Wyoming, Colorado, and Dakota.

SOCIETIES AND ACADEMIES.

LONDON.

Royal Society, January 9.-"A Milk Dentition in Orycte. By Oldfield Thomas, Natural History Museum. Comunicated by Dr. A. Günther, F. R.S.

the few Mammalia in which no trace of a milk dentition

has been found, Orycteropus, the Aard-Vark, has always occupied a prominent place, owing partly to the peculiar structure of its prominent teeth, and partly to its very doubtful systematic position.

An opportunity has now fallen in my way of proving that it has after all two sets of teeth, those of the first, or milk set, being rudimentary, and probably quite functionless, but nevertheless so far developed as to be all completely calcified, and to be for the most part readily distinguishable by form and position from those of the second or permanent set.

Among the collections in the Natural History Museum thereare two very young females of Orycteropus afer in spirit, presented by Sir Richard Owen, and it is in these that the milk teeth now to be described occur. The larger of the two measures 18 inches in total length, and the smaller 14 inches.

Each of these specimens has a complete, although rudimentary, set of milk teeth, extending the whole length of the maxillary bones above, and along a rather shorter portion of the mandible below. None, however, are observable in the premaxillæ, or in the corresponding anterior part of the mandibles. The teeth are all quite minute, and it is doubtful whether they would ever have cut the gum.

In the upper jaw there appear to be normally no less than seven milk teeth. Of these the most posterior is by far the largest, has a rudimentary crown, and two distinct roots, anterior and posterior. The others are simple and styliform.

In the lower jaw there are four milk teeth only, of which, again, the most posterior is more or less molariform.

As to the structure of the milk teeth, a horizontal section of the last upper one, ground down in the dry state, presents numerous large openings which are obviously the sockets into which pulp-papille have extended, so that the milk teeth show a commencement of the remarkable histological structure characteristic of the permanent teeth.

But important as a knowledge of the presence of a milk dentition in Orycteropus is, it does not at present render any easier the difficult questions as to the phylogeny and systematic position of that animal. Although called an Edendate, it has always. been recognized as possessing many characters exceedingly. different from those of the typical American members of the order. It has in fact been placed with them rather on account of the inconvenience of forming a special order for its reception than because of its real relationship to them. Now, as they are either altogether toothless or else homodont and monophyodont (apart from the remarkable exception of Tatusia), it seems more than ever incorrect to unite with them the solitary member of the Tubulidentata, toothed, heterodont, and diphyodont, and differing from them in addition by its placentation, the anatomy of its reproductive organs, the minute structure of its teeth, and the general characters of its skeleton.

But if Orycteropus is not genetically a near relation of the Edendates, we are wholly in the dark as to what other Mammals it is allied to, and I think it would be premature to hazard a guess on the subject. Whether even it has any special connection with Manis is point about which there is the greatest doubt, and, unfortunately, we are as yet absolutely without any paleontological knowledge of the extinct allies of either. Macrotherium even, usually supposed from the structure of its phalangeal bones to be related to Manis, has lately proved (see Osborn, American Naturalist, vol. xxii. p. 728, 1882) to have the teeth and vertebræ of a Perissodactyle Ungulate, and one could not dare to suggest that the ancestors of Manis or Orycteropus were to be sought in that direction. Lastly, as the numerous fossil American Edentates do not show the slightest tendency to an approximation towards the Old World forms, we are furnished with an additional reason for insisting on the radical distinctness of the latter, whose phylogeny must therefore remain for the present one of the many unsolved zoological problems.

Physical Society, January 17.-Prof. W. G. Adams, VicePresident, in the chair.-Owing to the unavoidable absence of Mr. F. B. Hawes, his paper on a carbon deposit in a Blake telephone transmitter was postponed.-Dr. S. P. Thompson made a communication on electric splashes, and illustrated his subject by beautiful experiments on the production of Lichtenberg's figures. The author has recently investigated these phenomena as modified by varying the conditions under which

On this subject see especially Flower, "On the Mutual Affinities of the Animals composing the Order Edentata," Zool. Soc. Proc., 1882, p. 358 et

seqq

the figures are obtained, and has arrived at the following conclusions: (1) the nature of the dielectric plate does not change the character of the figures produced, and (2) the nature of the powders used seems to have no material effect on their shape. In the course of his experiments he has found a mixture of sublimed sulphur and lycopodium to give better figures than the red lead and sulphur usually employed, and also that a large and highly polished knob is advantageous, particularly when the Leyden jar is charged negatively. Sometimes when obtaining negative figures, nebulous patches occur, and these were attributed to the so-called electric winds sent off from roughnesses on the knob when not sufficiently well polished. If instead of bringing the knob in contact with the plate, it is only brought near to it, then a peculiar figure closely resembling a 'splash" results. A positive splash consists of short lines radiating from the point of approach, whilst a negative splash is made up of more or less rounded spots which become elongated in a radial direction as their distance from the centre of the splash increases. Negative splashes are, however, much more difficult to produce than positive ones. When viewed in the dark, the discharge producing the splash is seen to consist of a bundle of small sparks which branch outwards on approaching the plate. In conclusion the author remarked that roughnesses on a conductor produced more electric winds when the conductor is charged negatively than when positively charged, and invited the opinions of members as to the causes of the differences observed between positive and negative electricity. Prof. Rücker said he had recently obtained figures produced by discharges on photographic plates. Generally he observed that negative discharges produce roundish patches, whilst positive ones give more filamentary figures. On passing a spark across a glass plate covered with lampblack, its trace was found to have a black core at one end, whilst the other was quite clear. He also made remarks on the distinctive character of the positive and negative discharges in partial vacuo, and considered investigations as to the causes of such differences to be of great importance. Prof. Adams thought any attempt to discover the causes of such differences as those noted in the paper was to be commended, for the well-known fact that it is more difficult to insulate a negative charge than a positive one has long needed an explanation.-A paper on galvanometers, by Prof. W. E. Ayrton, F. R. S., T. Mather, and W. E. Sumpner, was read by Prof. Ayrton. In fitting up the Physical Laboratories of the Central Institution of the City and Guilds of London Institute, the authors have had occasion to obtain galvanometers of various types and patterns, some of which have been made to special designs, and specimens of instruments embodying recent improvements were exhibited at the meeting. The question as to whether fairly sensitive galvanometers should be astatic or nonastatic was answered in favour of the former system, from the fact of its being less affected by external magnetic disturbances, and the greater ease with which great sensibility may be obtained. The usual method of placing the mirror inside the coil was shown to be undesirable, and in the newer forms of instruments Mudford's improvement of placing the mirror outside the coils has been adopted; the space near the axis of the coil being nearly filled with wire. It was also shown that if wire be wound in a certain approximately spheroidal space near the magnets, then these convolutions will tend to oppose the more distant portions of the coil; however, by winding the two parts in opposite directions they conspire to deflect the magnet. Details as to methods of supporting the coils were then discussed, and the importance of fitting them in boxes mounted on hinges or otherwise, so as to be readily removable, was pointed out. A galvanometer devised for teaching purposes, and provided with variable damping arrangements was described, in which the damping is effected by enclosing the mirror in a glass celi whose sides can be caused to approach or recede by turning a milled head outside the instrument. This arrangement enables the damping to be varied between wide limits, and its effect on the swing produced by a given discharge can be determined. The instrument is also serviceable both as an ordinary damped galvanometer, or as a fairly ballistic one. In measuring quantities of electricity by the first swing of a galvanometer needle, a correction has usually to be introduced for damping; this correcting factor is simple enough when the damping is small, but becomes more complicated as the damping increases, and to facilitate the calculations a table of values of the factor for various values of A (the logarithmic decrement) has been calculated. From this it appears that, for values of a less than o'5, the value of the factor is very nearly (+), the correction usually employed. Improvements in

methods of insulating the coils and terminals of galvanomet. required for insulation tests were next described, the principle which may be gathered from Figs. 107 and 108 in Prof. Av "Practical Electricity." A special form of instrument for hig insulation work was exhibited, in which the copper resistance the coils is nearly 400,000 ohms, and the shortest path alwhich surface leakage can take place from the coils to the bar the instrument is between 30 and 40 inches of ebonite artificial) dried by sulphuric acid. This is attained by supporting the from two corrugated ebonite rods which depend from a brass ne carried on the top of three corrugated pillars fixed to the base pla The instrument was constructed to drawing and specification Messrs. Nalder Brothers, but the method of supporting the 's was suggested by Messrs. Eidsforth and Mudford. With re ference to the proportionality of deflection to current in reflectie: galvanometers, it was pointed out that ordinary instrume may differ as much as 2 per cent. within the limits of the s hence showing the necessity for calibration when any approac accuracy is desired. Galvanometers of the D'Arsonval type sup times differ from proportionality quite as much as the one al v referred to, but by fitting such instruments with curved p pieces, and allowing the coil to hang freely from the top susp sion, a proportionality true to less than o'15 per cent. has be attained over a scale about 30 inches long. Coming to the qu tion of sensitiveness, the importance of keeping the wire as as possible to the magnets was brought prominently forward, well as the necessity of reducing the "figures of merit” of vus instruments to the same standard, in comparing their sensibilit The standard adopted as most convenient and closely appro ing to practical usage is arrived at by supposing the distance the mirror from the scale to be equal to 2000 scale divisions, a the sensibilities for current and quantity are given as divisions per micro-ampere, and scale divisions per micro como respectively. The period of oscillation is also taken into ac A table showing the resistances, sensibilities, coefficients self-induction and volumes of the coils of various instrum together with the relations existing between them, accompan the paper, and from this it appears that in the best astatic d' coil instruments, of from 10,000 to 30,000 ohms resistance, de number of scale divisions per micro-ampere may reach 400 time the resistance to the th power (400 R) when the period a to seconds. In obtaining data of various instruments the authen have consulted, amongst others, Prof. Threlfall's paper on t measurement of high specific resistances, in the Phil. M& December 1889, and noticed two serious errors. The first these makes an instrument constructed according to Mat Gray's pattern nine times less sensitive than it actually -. whilst the sensibility of a form recommended in the pater a given seventeen times too great. On account of the lateness the hour, the discussion was adjourned till February 6, bec which time it is hoped that a fairly full abstract will app in the technical papers.

Geological Society, January 8.-W. T. Blanford, F.R.S President, in the chair. The following communications w read :-On some British Jurassic fish-remains referable to t genera Eurycormus and Hypsocormus, by A. Smith Woodwa Hitherto our knowledge of the Upper Jurassic fish fauna been mainly derived from specimens found in fine lithograph stones, where the various elements are in a state of extracompression. Within the last few years remains of similar ta have been discovered in the Oxford and Kimeridge Clay & England, and these are of value for precise determination certain skeletal features in the genera to which they belo The author described Eurycormus grandis from the Kimer Clay of Ely, a large species which makes known for the b time the form and proportions of several of the head-boots this genus. A technical description of all the bones the char ters of which are distinguishable was given, and the author c cluded that there is considerable similarity between the head Eurycormus and the recent Ganoid Amia, even to minule pou of detail. He further described Hypsocormus tenureitri p II. Leedsii from the Oxford Clay of the neighbour of Peterborough, the osteology of this genus not hav as yet been elucidated. Portions of the jaws have been d covered, affording valuable information as to the form dentition of the principal elements. These jaws are not prai paralleled by any other Jurassic genus, though they posses resemblance to Pachycormus, as also to the Upper Cretace genus, Protosphyrana. The President remarked that Amy 21

freshwater genus, and inquired whether the fossil fish was freshwiter or marine. Mr. E. T. Newton remarked upon the great interest and importance of the paper. The author, in reply to the President's question, said that the old Ganoids were marine, dit was only in more recent times that they had become re tricted to fresh water.-On the Pebidian volcanic series of St. and's by Prof. C. Lloyd Morgan. After a brief sketch of the principal theories that have been propounded, the ..ther concluded that our knowledge of this series has not ret reached “a satisfactory position of stable equilibrium." He own communication was divided into three sections. The Relation of Pebidian to Cambrian: There are four localiwhere the junction is described-Caerbwdy Valley, St. Nor's Bay, Oguf Golchfa, and Ramsey Sound. The stratirhy of the second of these was given with much detail, and srited. The author concluded that here, together with Car signs of local or contemporaneous erosion, the general raleism of the strike of Pebidian and Cambrian is most marked. There is no evidence of any bending round of the glomerate against the strike of the Pebidians. The stratiapical evidence in each of the localities having been concred, together with the evidence offered by the materials of Cambrian conglomerate and local interstratification with the vianic beds (the interdigitation at Carnarwig being well arsed), he concluded that there was no great break between The conglomerate and the underlying Pebidians. The upperus Febidian already foreshadowed the sedimentary conditions : the Harlech strata, and the change emphasized by the conglomerate was one that followed volcanic conditions after no great lapse of time. Hence the relation of the Pebidian to the mbrian is that of a volcanic series, for the most part subarine, to succeeding sedimentary strata-these strata being trxiuced by a conglomerate formed in the main of foreign nenbies borne onward by a current which swept the surface of, roded channels in the volcanic tuffs and other deposits. I was disposed to retain the name Pebidian as a volcanic es in the base of the Cambrian system. The Pebidian SucWith the exception of some cinder-beds, which appear ute subaerial, the whole series was accumulated under water. There is no justification for making separate subdivisions; the is consists of alternating beds of tuff of varying colour and city, the prevailing tints being dark green, red-grey, and ght sea-green. In the upper beds there is an increasing start of sedimentary material, and more rounded pebbles re found. Basic lava-flows occur, for the most part, in the er beds. Detailed work, laid down on the 6-inch Ordnance appears to establish a series of three folds-a northern cline, a central syncline, and a southern anticline-folded to form an isocline, with reversed dips to the south-east. The axis of folding is roughly parallel to the axis of St. David's montory. The total thickness is from 1200 to 1500 feet. The author devoted a considerable number of pages to further tails concerning this series of deposits. He failed to find the eged Cambrian overlap. "The probabilities are that it is by hults between Khoson and Porth Sele, and not by overlap, the displacement of the conglomerate has there been tected." Also at Ogof Goch it does not rest upon the quartzte breccia and sheets (group C, of Dr. Hicks), but is faulted mit them. A section was devoted to the felsitic dykes, and was suggested that they may be volcanic dykes of Cambrian The Relation of the Pebidian to the Dimetian: The chor has not been able to satisfy himself of the existence of he Arvonian as a separate and distinct system. He notes the nction of Pebidian and Dimetian in Porthlisky Bay and the Allen Valley at Porth Clais, at neither of which places are there tfactory evidences of intrusion. At Ogof Llesugn the inrive character of the Dimetian was strongly impressed upon b. He criticized the mapping of Dr. Hicks, and pointed out the difficulties which present themselves in the way of mapping Dimetian ridge as pre-Cambrian. He pointed out that not ngle pebble of Dimetian rock, such as those now lying on the beach in Porthlisky Bay, is to be found in the conglomerate. He concluded that the Dimetian is intrusive in the southern mb of the isocline, and that there are no Archæan rocks in situ. After the reading of this paper there was a discussion, in which e President, Dr. Hicks, Prof. Blake, Prof. Hughes, and Mr. Williams took part.

SYDNEY.

Royal Society of New South Wales, November 6, 1889. -Monthly meeting.-Prof. Liversidge, F.R.S., President, in

the chair.-The Chairman announced the death of the Rev. J. E. Tenison-Woods, who had been an honorary member of the Society since 1875.-The following papers were read :-Aids to the sanitation of unsewered districts, poudrette factories, by Dr. J. Ashburton Thompson.-Notes on Goulburn lime, by E. C. Manfred.-Notes on some minerals, &c., by John C. H. Mingaye.

December 4.-Monthly Meeting.-Prof. Liversidge, F.R.S., President, in the chair.-The following papers were read:Well and river waters of New South Wales, by W. A. Dixon. -The Australian aborigines, by Rev. John Mathew.

PARIS.

Academy of Sciences, January 20.-M. Hermite in the chair. On the various states of the carbon graphites, and on the chemical derivatives corresponding to them, by MM. Berthelot and P. Petit. The graphites, when oxidized by the wet process at a low temperature, form ternary compounds, one of whose terms has been discovered by Brodie. But M. Berthelot has since shown that there exist several chemically distinct graphites, each forming a particular graphitic oxide, which yields a corresponding hydrographitic and pyrographitic oxide, and which may be recovered with all their primitive properties. These various graphites and the series of corresponding compounds have been studied, first by their composition and behaviour, and in a second memoir by the measurement of the heats of combustion and formation.-Remarks on the formation of the nitrates in plants, by M. Berthelot. The author points out that the facts established by Haeckel and Lundström, taken in connection with his own observations, tend to show an affinity between the microbes present in the soil and those developed in the plant. This applies to the microbes which fix the nitrogen of vegetable humus and the leguminous plants, as well as to those which similarly form the nitrates in amaranthus, sterculia, the coffee shrub and vegetable humus.-Note on a fundamental point of the theory of polyhedrons, by M. de Jonquières. The paper deals with Euler's famous formula S + H = A + 2, and shows that it is applicable, and intended by Euler to be applicable, to all polyhedrons without exception, and not restricted to any particular class, as supposed by Legendre, Cauchy, and others. -Ephemerides for the search of the periodical comet of d'Arrest on its return in 1890, by M. Gustave Leveau. Having previously obtained the elements for the years 1870, 1877, and 1883, by allowing for the disturbing influence of Jupiter, Saturn, and Mars, M. Leveau here supplies those for 1890 (February 25, mean Paris time) by studying the disturbing effects produced by Jupiter in the interval between 1883 and 1890.-Observations of Swift's comet made at the Observatory of Nice with the 0.38 m. equatorial, by M. D. Eginitis.-On the solar statistics for the year 1889, by M. Rud. Wolf. From the solar observations made at Zurich and the magnetic observations recorded at Milan, the author has constructed a table of monthly means showing that both the relative numbers and the magnetic variations have continued to diminish during 1890. But he thinks that the retrograde movement will soon cease, and that we probably entered the minimum period towards the end of last year.-On the theory of the figure of the planets, by M. M. Hamy. An attempt is here made to realize theoretically the conditions of a system answering to M. Poincaré's remarkable theorem published in the Comptes rendus for June 1888.-On the integration of an equation with partial derivatives, by M. Zaremba. The paper deals with an equation of the form

where

and are two functions whatsoever of x+y, and shows that the determination of the general integration may be reduced to the integration of an ordinary linear differential equation of the second order, and to quadratures.-On the variation of the resistance of bismuth in the magnetic field, by M. A. Leduc. The author here continues his studies of the electric resistance of bismuth as affected by varying temperature.— Calculation of the compressibility of nitrogen up to 3000 atmospheres, by M. Ch. Antoine. The results of fresh calculations are here summed up in a table resuming all the data relative to the pressure of nitrogen up to a pressure of 3000 atmospheres.On the combinations of the metals of the alkalies with ammonia, by M. H. W. Bakhuis Roozeboom. An explanation is offered of the curious phenomena mentioned by M. Joannis in his recent