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purposes of Koch's and Hansen's processes is also discussed. It is obvious that the organisms to be feared in a brewery are those which will flourish in wort or beer, and that the mere knowledge of the number of bacteria in any given water as revealed by gelatine plate cultures is but of little use. Hence Hansen and his pupils reject for such examinations gelatine-peptone, substituting sterilised wort and beer as a culture material. An interesting table is given showing the different bacteriological results obtained in the use of gelatine-peptone, gelatine to which wort had been added, wort alone, and beer. For example, whereas a particular brewing-water yielded by gelatine-peptone about 8000 colonies per c. c., the majority of which were bacteria; gelatine mixed with wort gave about 14, all being moulds; in wort 5'4 were found, consisting of bacteria and moulds, whilst sterilised beer gave only o'8 for the c. c., and only moulds. Holm points out that to estimate the value of a water for brewing purposes a note should also be made of the rate at which the organisms develop in the wort or beer, for should signs of growth only declare themselves after four or five days in the laboratory under favourable conditions of temperature and in the absence of competing forms, it is not unnatural to expect that their vitality, under the more rigorous conditions imposed during brewing operations, would be so far impaired that their development, if taking place at all, would only be accomplished with great difficulty. Although instances occurred in which even after the lapse of seven days growths first made their appearance, yet in the majority of cases the incubation of the wort-flasks for one week was sufficient. Holm is of opinion that the use of other culture materials besides wort is unnecessary, as all the organisms which successfully develop in beer can also grow in wort. Moreover, it was found that in the process of sterilisation to which the beer was submitted a considerable proportion of its alcohol was lost, thus diminishing its natural bactericidal properties. A beer containing 5 to 6 per cent. of alcohol, after sterilisation, had this reduced to 2.8 per cent., although it even then proved a very unfavourable medium for the development of ordinary water bacteria. As a practical outcome of his experiments Holm emphasises the necessity of a careful selection of the site for the erection of the water-reservoir attached to a brewery. The reservoirs of the old brewery at Carlsberg are placed in the immediate vicinity of the storehouses for grain and malt, consequently in this water a far larger number of moulds were met with than in the water examined from differently situated reservoirs supplying the laboratory and another brewery. But although moulds usually predominate, yet they are not so much to be feared as the bacteria, more especially those which are found in the fermentation chamber, for although they are unable to assert themselves to any considerable extent in the beer preserved in the store cellar, yet when it is drawn off and thus aërated, and the temperature raised by its transference to bottles or small casks, these organisms can develop with an astonishing rapidity, and produce great mischief.

UNIVERSITY AND EDUCATIONAL

INTELLIGENCE.

CAMBRIDGE.-Dr. Shore, of St. John's College, late Examiner in Physiology, has been elected a member of the Special Board for Medicine; Dr. A. Macalister, F.R.S., St. John's, has been appointed an elector to the Professorship of Chemistry; Dr. Ferrers, F. R.S., Master of Gonville and Caius, an elector to the Plumian Professorship of Astronomy; Prof. Newton, F.R.S., Magdalene, an elector to the Professorship of Anatomy; Dr. Phear, Master of Emmanuel, an elector to the Professorship of Botany; Dr. R. D. Koberts, Clare, an elector to the Woodwardian Professorship of Geology; Mr. P. T. Main, St. John's, an elector to the Jacksonian Professorship of Chemistry, &c.; Mr. R. T. Glazebrook, F.R.S., Trinity, an elector to the Professorship of Mineralogy; Mr. F. Darwin, F. R. S., Reader in Botany, an elector to the Professorship of Zoology and Comparative Anatomy; Mr. W. D. Niven, F.R.S., Trinity, an elector to the Cavendish Professorship of Physics; Dr. Phear, an elector to the Professorship of Mechanism; Prof. Liveing, F.R.S., St. John's, an elector to the Downing Professorship of Medicine; Dr. P. H. Pye-Smith, F.R.S., an elector to the Professorship of Physiology; and Sir G. M. Humphry, F.R.S., an elector to the Professorship of Pathology.

SCIENTIFIC SERIALS.

American Journal of Science, February.-Isothermals piestics, and isometrics relative to viscosity, by C. Baras substance experimented upon was marine glue, and its visi at different pressures and temperatures was measured by at piration method, the substance being forced through steel. 10 cm. long and 0.5 to 1 cm. in diameter under presse high as 2000 atmospheres. It was found that in proportion the viscosity of a body increases with fall of temperat isothermal rate of increase with pressure also increases. Spect approximately, the rate at which viscosity increases with sure at any temperature is proportional to the initial va at that temperature, and, conversely, the rate of decrease temperature is proportional to the actual temperature and pendent of the pressure. An interesting result is that int pressure phenomena at least 200 atmospheres must be per degree Centigrade, in order that there may be no chang viscosity." Potential," a Bernoullian term, by Ge Becker. Datolite from Loughboro, Ontario, by L. V. F -A new machine for cutting and grinding thin sections an and minerals, by G. H. Williams.-Stannite and some alteration products from the Black Hills, S.D., by i Headden.-Occurrence of hematite and martite iros ute Mexico, by R. T. Hill, with notes on the associated rocks, by W. Cross.-Casium lead and potassium-lead by N. L. Wells.-Ceratops beds of Converse C Wyoming, by J. B. Hatcher.- Use of planes and knifeng pendulums for gravity measurements, by T. C. Mende The employment of a pendulum to which the plane is a instead of the knife-edge presents several advantages plane may be accurately adjusted at right angles to the .. simple optical methods. A pendulum carrying a plate 2 of a knife-edge is vastly less liable to injury, and the kne being no longer an integral part of the vibrating mis reground or replaced at will. The length of the pendu more capable of accurate determination, since the en duced by the yielding of the edge under pressure is el The disadvantage due to the uncertain position of the oscillation can be mechanically got rid of by a proper tion of the raising and lowering apparatus, and expert shows that the period in the course of twelve sets of 525 an hour each does not vary by as much as one part in 15 The best angle for the knife-edge was found to be shoc the material used being agate.-Preliminary note on the of cloudy condensation, by C. Barus. If saturated c allowed to pass suddenly from a higher to a lower ten in uniformly temperatured, uniformly dusty air, a succe colours is seen by transmitted white light which, take verse order, are absolutely identical with the colours of Ne rings of the first two orders.-Lines of structure in the W bago Co. meteorites and in other meteorites, by E Newton (reprinted in this issue).-Preliminary note meteorite from Japan, by Henry A. Ward.-Restura Anchisaurus, by O. C. Marsh (see Note, p. 349).

American Journal of Mathematics, vol. xiv. No. 4 more, 1892).--The main object of the note on the use mentary curves in isogonal transformation, by R. A (pp. 291-300), is to show how the problem of representin plane conformably upon another, using any real functice. structing supplementary curves from given tracings of the variable, may be made to depend upon the problem sponding principal curves. It is well illustrated by four drawn figures. In her memoir (pp. 301-325) on the singularities of plane curves, Miss C. A. Scott goes or to some extent previously occupied by Profs. Cayley S. Smith in writing on the same subject (cf. also pa Brill and Nöther in the Math. Annalen, vols. ix. x. Nöther's results are presented in analytical form, dependence on geometrical ideas even when geometric are used.' The author brings out his results more de making use of Dr. Hirst's method of quadric inversion is accompanied by twenty-seven drawings of curves. M Metzler, writing on the roots of matrices (pp. 326–377-7 a modification of Dr. Forsyth's method of proving "identical equation" ("Messr. of Mathematics," va prove Sylvester's law of latency and Sylvester's theorem also investigates the existence of roots of matrices for indices, and in particular the roots of nilpotent mai us

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he specimen described in this memoir was found in the year in a bed of clay, which was cut through in making a railat Invercargill, near the southern end of the Middle Island ew Zealand. Originally, this meteorite appears to have about the size of a man's fist, and to have weighed four or sounds, but it was broken up, and only a few small fragments been preserved. The stone evidently consisted originally 1 intimate admixture of metallic matter (nickel-iron) and of material, but much of the metallic portion has undergone ition. Microscopic examination of thin sections shows that tony portion, which is beautifully chondritic in structure, ins olivine, enstatite, a glass, and probably also magnetite; through these stony materials the nickel-iron and troilite istributed. The specific gravity of portions of the stone ound to vary between 3.31 and 3'54, owing to the unequal bution of the metallic particles. A partial chemical exation of this meteorite was made by the author and Mr. s Allen, but the complete analysis has been undertaken by L. Fletcher, F.R.S., of the British Museum. The analysis, when finished will be communicated to this Society, has so far as to show that the percentage mineral composition Makariwa meteorite may be expressed approximately by llowing numbers: nickel-iron 1, oxides of nickel and iron oilite 6, enstatite 39, olivine 44.

ysical Society, January 27.-Walter Baily, Vice-Presiin the chair.-Prof. S. P. Thompson, F.R.S., made a unication on Japanese magic mirrors, and exhibited rous specimens showing the magic properties. Referring e theory of the subject, he said the one now generally ted was that proved by Profs. Ayrton and Perry in 1878, howed that the patterns seen on the screen were due to ences in curvature of the surface. The experiments he now ht forward fully confirmed their views. Brewster had ained that the effects were due to differences of texture in rfaces causing differences in absorption or polarisation, but ct that the character of the reflected image depended on nvergency or divergency of the light, and on the position screen, showed this view to be untenable. Another proof differing curvature theory was then given by covering a ese mirror with a card having a small hole in it. On g the card about, the disc of light reflected from the exportion varied in size, showing that the curvatures of porOf the surfaces were not the same. The same fact was 1 by a small spherometer, and also by reflecting the light g through a coarse grating from the mirror, the lines being distorted. To put the matter to a test demanded by ter, he had a cast taken from a mirror by his assistant, ousseau; this had been metallised, silvered, and polished, w gave unmistakable evidence of the pattern reflected he original. The true explanation of how the inequalities ature were brought about during manufacture had also given by Profs. Ayrton and Perry, but there were some ons of detail on which difference of opinion might exist. e Prof. Govi had noticed that warming a mirror altered its lities. A thick mirror which gave no pattern whilst cold bed one on being heated, was shown to the meeting. hompson also showed that a glass mirror having a pattern the back developed magic properties when the mirror nt. When made convex the reflected pattern was dark ght ground, and when made concave, light on a dark Warming ordinary mirror-glass by a heater whose suras cut to a pattern gave similar effects. Very thick

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glasses could be affected in this way. On passing a spirit lamp behind a strip of mirror, a dark band could be caused to pass along the screen illuminated by light reflected from the mirror. By writing on lead foil and pressing the foil against a glass mirror by a heater, the writing was caused to appear on the screen. Prof. Thompson had also found that Japanese mirrors which are not "magic" when imported, could be made so by bending them mechanically so as to make them more convex. In conclusion, he showed a large mirror 15" x 11", the reflection from which showed the prominent parts of the pattern on its back with the exception of two conspicuous knobs; these knobs gave no indication of their existence. Prof. Ayrton said the simple mechanical production of the magic property described by Prof. Thompson led him to think that some experiments on "seeing by electricity" by the aid of selenium cells which Prof. Perry and himself made some years ago, might lead to some result if repeated with thinner reflectors. Speakpointed out that if metal be removed by pressure a bright ing of the effect of scratching the back of a Japanese mirror, he image was seen, whilst if removed chemically a dark image resulted. Since the original paper on the subject was written he had been led to modify his views as to the effect of amalgamation, for some time ago he showed the society how brass bars were bent if one edge be amalgamated, thus proving that enormous forces were developed. He now regarded amalgamation as an important part of the manufacture. Mr. Trotter inquired if it had been proved that there was no difference in the metal in the thick and thin parts? One would expect the thin parts to be harder and polished away less. After some remarks by Mr. J. W. Kearton and Major Rawson, Prof. Thompson said the magic effects produced by heating the back of a glass mirror remained for a short time after the heater was removed. The question of whether differences in hardness of the thick and thin parts of a mirror were of consequence in the production of the magic property had been tested by using sheets of brass thickened by pieces soldered to the back as mirrors, and found to be unimportant. Prof. Ayrton also described an experiment pointing to the same conclusion. Mr. W. F. Stanley read a paper on the functions of the retina (i.) The Perception of Colour. Referring to Young's three-nerve theory of colour-sensation, the author said Prof. Rutherford had pointed out that there was no necessity to assume that different nerves conveyed different colour-sensations, for as a telephone wire would transmit almost an infinite variety of sound vibrations, so the nerves of the retina were probably equally capable of conveying all kinds of light vibrations. Prof. Rutherford had further pointed out that the image of a star could not possibly cover three nerve-terminals at once, and therefore could not be seen as white if Young's theory was correct. The author then described Helmholtz's experiments with a small hole in a screen illuminated by spectrum colours. For red illumination the greatest distance at which the hole could be seen sharply defined was 8 feet, and for violet 1 feet. When the hole was covered with purple glass, or with red and violet glasses superposed, and a bright light placed behind, the eye, when accommodated for red light, saw a red spot with a violet halo round it, and when focussed for violet light, saw a violet spot with circle of red. These experiments the author thinks show that the chromatic sense in distinct vision under critical conditions (i.e. where a single nerve or a small group of nerves is concerned) depends on the colours being brought to foci at different distances behind the crystalline lens. He also infers that the same focal position in the eye cannot convey simultaneously the compound impression of widely separated colours. Helmholtz's observations are further examined in the paper, and a series of zoetrope and colour disc experiments described which tend to show that the eye cannot follow rapid changes of colour. Changes from red to violet could be followed much more quickly than from violet to red. The red impressions were, however, more permanent. The observed effects were found to depend on the intensity of the light, and also on the distance of the eye from the coloured surface. Summing up his observations, the author infers that by systems of accommodation of the eye, the colours of the spectrum are brought to focus on special parts or points of the rods or cones of the retina, such focal points being equivalent, by equal depths or distances from the crystalline lens, to a focal plane formed across the whole series of nerve terminals. That all the rays of light from an object, or part of an object, of very small area and of any spectrum colour, will converge to

a point upon a nerve terminal, and that this terminal will be most excited by the light. At the end of the paper Dr. Stanley Hall's views of nerve structure are examined. Captain Abney thought the results of the zoetrope experiments were what one would have expected when pigmentary colours were used. To be conclusive, such experiments must be conducted with pure spectrum colours. The statement about the size of star images being less than that of a nerve terminal would probably need revision. Speaking of colour vision, he said the modern view was to regard light as producing chemical action in the retina, which action gave rise to the sensation of colour. On the author's theory he could not see how colour-blindness could be explained. Mr. Trotter said he understood Helmholtz to have proved that nerves could distinguish quantity, but not the quality of a stimulus. Since the speed at which stimuli travelled to the brain was about 30 metres a second, the wave length of a light vibration, if transmitted in this way, would be very small. Taking Lord Kelvin's estimate of the minimum size of molecules of matter, it followed that there must be many wave lengths in the length of a single molecule. This, he thought, hardly seemed possible. Mr. Lovibond pointed out that the observations referred to by the author could be equally well explained on the supposition that six colour sensations existed. The confusion of colours he had mentioned arose from lack of light. Mr. Stanley replied to some of the points raised by Captain Abney. In proposing a vote of thanks to Mr. Stanley, the chairman said it had been shown that light could be resolved into three sensations, but it was not known how this resolution occurred. Prof. S. P. Thompson said the gist of Mr. Stanley's paper seemed to be that lights of different colours were concentrated at points situated at different depths in the retina, the violet falling on the part nearest the crystalline lens, and the red furthest away. Another view of the action was that the different sensations might be due to the vibrations of longer wave length having to travel greater distances along the nerve terminals before they were completely absorbed.

a function of the letters a, a, an......; b, b1, b... ; &c. corresponding to the marks a, b, . &c. of the simple contained in the compound form represented by the grip latter factor being an invariant of the quantics

(α, a, a,..........a ̧)(x, y)-
(bo, by, b.bg)(x, y)s
&c., &c.

where a is the valence of the simple forms of mark a, sb here supposed to be all of the same valence, and similarly u case of B, y, &c.

In this second part a method of algebraically represe invariants is considered, which is directly derivable i method of the first part, and was suggested by the graphs differs essentially from the earlier method in that it is dent of the use of polar elements. It shows, moreover, b graphs may be regarded as absolutely equivalent to the ants they represent, in lieu of being equivalent to those a ants multiplied by a number of polar elements. This e method deals in the first instance with "primary" i i.e. invariants of two or more quantics linear in the coet of each. If these quantics are (ao, as, ag ....a.)(x, y)a (bo by, ba... bp)(x, y)s

and we take

&c., &c.,

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we may express any primary invariant by an expression
sum of two or more expressions, consisting of the pro
differences of the operators a, b,..... operating upon the
of the corresponding leading terms, ao, bo, &c. Thus
(a - b)2ab=ab ̧ ¬ 20161 +a‚þ1⁄2

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linear in the coefficients of each; and
(a−b)2(a–c)ab=azbyło abf1-20+243

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Mathematical Society, January 12.-Mr. A. B. Kempe, F.R. S., President, in the chair. -The President (Prof. Elliott, F.R. S., Vice-President, in the chair) read a paper on the appli- is an invariant of the two quantics cation of Clifford's graphs to ordinary binary quantics (second part). In the first part it was pointed out that by some small modifications and a recognition of the fact that the covariants of f(x, y) are invariants of the two quantics ƒ(X, Y) and (Xy-Yx), the theory of graphs, which had been left in an unfinished state by the late Prof. Clifford, furnished a complete method of graphically representing the invariants (and therefore the covariants) of binary quantics. The method as modified depends essentially on the fact that any invariant, when multiplied by a suitable number of polar elements U, U',V,V', &c., can be expressed as a "pure compound form" (or sum of two or more such forms), the product of a number of "simple forms." Each of the latter has a "mark," viz. one of the letters a, b, c,...... and has also a certain valence, 0, 1, 2, 3, &c. and these being given it is fully defined, e.g., the simple form of mark a and valence 3 is graphically

having three radiating bonds, and is algebraically

a1 UVW+a1 (U'VW +UV'W+UVW') + a„ (UV'W' +U'VW' + U'V'W) + az U'V'W',

the pairs of polar elements U, U'; V,V'; and W, W', corresponding to the three bonds of the graphical representation. A pure compound form is graphically represented by a number of simple forms having their bonds connected so that there are no free ends. If in the algebraical expression of a compound form two simple forms both contain the pair of polar elements U, U', there will be a bond connecting their graphical representations; if the two simple forms both contain two pairs of such elements, viz. U,U' and V,V', there will be two bonds connecting their graphical representations and so on; if they contain no common pair their graphical representations will have bond connecting them. A pair of polar elements will appear in two simple forms only, so that each bond in the graphical representation of a compound form corresponds to a distinct pair of polar eleIf the algebraical expression corresponding to a graph be multiplied out, it will be found to consist of two distinct factors, viz. :-(1) the product of all the polar elements, and (2)

ments.

is a similar invariant of the three quantics
≤ a1r3 + 3a1x2y + 3a‚xy2+azv1⁄23
bot +261xy+b2

These two invariants are graphically represented by

b

and (b

a

respectively, where the relation between the algebraic
graphical expressions is obvious, viz.
to every letter
algebraical representation there corresponds a nucleus 5.
the mark p, and to every factor (p-q) in the algebraica
tation there corresponds a bond connecting the nude
p and q.

We can pass to invariants of higher degrees in the c
of the various quantics by substituting like coefficients or
Thus, if we make boa, b1 =a, bag, the primary
ab2a11+ag
becomes the invariant of degree 2

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It bears, however, a definite relation to the first of these ee quantics, viz. it is a seminvariant of that quantic, being fact the source of its cubic-covariant J. The paper points that all seminvariants are thus invariants of two or more intics, and can therefore be represented by graphs; the ference between a graph representing an invariant of a intic and one representing a seminvariant of the same quantic isisting merely in this, that the simple forms, i.e. the small cles or nuclei of the graphs in the former case are all of the le "valence," i.e. have the same number of bonds, while in latter, though of like marks, they differ in valence. The ssification of seminvariants, according to the valences of the ple forms composing them, or, in other words, according to orders of the quantics of the systems of which they are rectively invariants, obviously throws considerable light upon

r structure.

The paper also deals with the breaking up of graphs into pler ones; and gives a theorem upon the subject which leads ome interesting results. It points out, moreover, how the phs representing the sources of covariants can be instaneously derived from those representing the covariants them.

es.

oson.

In the evaluation of a certain surface-integral and its applicato the expansion of the potential of ellipsoids in series, Dr. in the vibrations of an elastic circular ring, by Mr. A. E. H. e. The ring is supposed to be of small circular section of us, and the elastic central-line a circle of radius a. There four ways of displacing the ring. A point on the central-line move along the radius of the circle which is its primitive 1, or perpendicular to the plane of this circle, or along the (ent to this circle; and the circular sections may be dised by rotation about the central-line. The modes of vibrafall into four classes, of which two are physically import:-Class I. Flexural vibrations in plane of ring.-These investigated by Hoppe in 1871 (Crelle, bd. lxxiii.). The ion of a point on the elastic central line is compounded of a lacement in and out along the radius and a displacement along tangent to the circle, so proportioned that the central-line ains unstretched, and the nodes of the former displacet are the antinodes of the latter. There must be at least wave-lengths to the circumference, and the frequency (p/2π) le mode in which there are n wave-lengths to the circumferis given by the equation

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hich E is the Young's modulus, and po the density of the erial. Except for the numerical coefficient this is precisely Har to the formula for the lateral vibrations of a straight bar e same material and section and of length ra (for which the amental tone has the same wave-lengths). The sequence omponent tones when n is very great is ultimately identical that of the tones of a free-free bar of length a, but the ence for the low tones is quite different to that for a bar. s II. Flexural vibrations perpendicular to the plane of the -It is found to be impossible to make the ring vibrate y so that each particle of the elastic central-line moves perCicular to the plane of the ring, unless at the same time the ons turn about the central-line through a certain angle. flexure perpendicular to the plane of the ring is always mpanied by torsion. As in Class I. there must be at least two e-lengths to the circumference, and the frequency of the = in which there are n wave-lengths to the circumference is n by the equation n2 (n2 – 1)2 E c I + σ + n2 Po a

= 1

-e a is the Poisson's ratio for the material and the other ants have the same meaning as before. (For most hard so is about 4.) Since n must be at least 2 the sequence of is very nearly the same as in the vibrations of Class I., The pitch is slightly lower, the ratio of the frequencies for gravest tones being which is very little less a comma. For the higher tones, as we should expect, there

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Putting zero we find the frequency of the purely radial vibrations. The pitch of any mode of extensional vibration of the ring is of the same order of magnitude as the pitch of the corresponding longitudinal vibration of a bar of length equal to half the circumference, the formula for the latter being in fact derived by writing n for I + n2. Class IV. Torsional vibrations.-The motion consists of an angular displacement of the sections about the elastic central-line accompanied by a relatively very small displacement of the points on this line perpendicular to the plane of the ring. When there are n wavelengths to the circumference the frequency is given by the formula

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=

E,

in which is the rigidity of the material. There is one symmetrical mode for which n is zero, and since 2μ (1+ σ) the frequency of this mode is√2 of that of the radial vibrathat for a straight rod of length equal to half the circumference, tions. The pitch of the torsional vibrations is comparable with the formula for the latter being in fact derived by writing no in Formulæ equivalent to those given in place of I++ n2. connection with Classes II. and IV. have been obtained by Mr. Basset (Proc. Dec. 1891), but he has not interpreted his results.

Entomological Society, February 8.-Mr. Henry John Elwes, president, in the chair.-The President announced that he had nominated Mr. F. DuCane Godman, F.R.S., Mr. Frederic Merrifield, and Mr. George H. Verrall as VicePresidents during the Session 1893-1894.-Mr. S. Stevens exhibited a specimen of Charocampa celerio, in very fine condition, captured at light, in Hastings, on September 26 last, by Mr. Johnson. Mr. A. J. Chitty exhibited specimens of Gib. bium scotias and Pentarthrum huttoni, taken by Mr. Rye in a cellar in Shoe Lane. He stated that the Gibbium scotias lived in a mixture of beer and sawdust in the cellar, and that when this was cleaned out the beetles disappeared. The Pentarthrum huttoni lived in wood in the cellar.-Mr. McLachlan exhibited a large Noctuid moth, which had been placed in his hands by Mr. R. H. Scott, F.R.S., of the Meteorological Office. It was stated to have been taken at sea in the South Atlantic, in about lat. 28° S., long. 26 W. Colonel Swinhoe and the President made some remarks on the species, and on the migration of many species of Lepidoptera.-Mr. W. F. H. Blandford exhibited larvæ and pupa of Rhynchophorus palmarum, L., the Gru-gru Worm of the West Indian Islands, which is eaten as a delicacy by the Negroes and by the French Creoles of Martinique. He stated that the existence of post-thoracic stigmata in the larva of a species of Rhynchophorus had been mentioned by Candèze, but denied by Leconte and Horn. They were certainly present in the larva of R. palmarum, but were very minute.-Mr. G. T. Porritt exhibited two varieties of Arctia lubricipeda from York; an olive-banded specimen of Bombyx quercus from Huddersfield; and a small melanic specimen of Melanippe hastata from Wharncliffe Wood, Yorkshire. Mr. H. Goss exhibited species of Lepidoptera, Coleoptera, and Neuroptera, sent to him by Major G. H. Leathem, ing expedition in Kashmi territory, Bengal. who had collected them, last June and July, whilst on a shootSome of the specimens were taken by Major Leathem at an elevation of from 10,000 to 11,000 feet, but the majority were stated to have been collected in the Krishnye Valley, which drains the glaciers on the western slopes of the Nun Kun range. Mr. Elwes remarked that some of the butterflies were of great interest.Mr. G. F. Hampson exhibited a curious form of Parnassius, taken by Sir Henry Jenkyns, K. C.B., on June 29 last, in the Gasternthal, Kandersteg.-Mr. J. M. Adye exhibited a long series of remarkable varieties of Boarmia repandata, taken last July in the New Forest. Mr. C. O. Waterhouse exhibited a photograph of the middle of the eye of a male Tabanus, showing square and other forms of facets, multiplied twenty-five times. Mr. R. Trimen, F.R.S., communicated a paper entitled "On some new, or imperfectly known, species of South African

Butterflies," and the species described in this paper were exhibited. Mr. T. D. A. Cockerell communicated a paper entitled "Two new species of Pulvinaria from Jamaica.' Mr. Martin Jacoby communicated a paper entitled "Descriptions of some new genera and new species of Halticidæ."

Linnean Society, February 2.-Prof. Stewart, President, in the chair.-On behalf of Mr. Thomas Scott, the Secretary read a report on the entomostraca from the Gulf of Guinea, collected by Mr. John Rattray.-Mr. H. Bernard gave an account of two new species of Rhax.-An important paper by Mr. Arthur Lister, on the division of nuclei in the mycetozoa, gave rise to an interesting discussion, in which Dr. D. H. Scott, Prof. Howes, and others took part.-This was followed by a paper on the structural differentiation of the protozoan body as studied in microscopic sections, by Mr. J. E. Moore. The meeting adjourned to February 16.

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Academy of Sciences, February 6.-M. de LacazeDuthiers in the chair.-On the variations in the intensity of terrestrial gravitation, by M. d'Abbadie. Observations begun in 1837 at Olinda (Brazil), on the variations in the direction of gravitational force also made its constancy doubtful. Experiments on falling bodies revealed irregularities similar to those described (last number) by M. Mascart. The closed barometer employed by the latter may be termed a brithometer.-On the preparation of carbon under high pressure, by M. Henri Moissan (see article).-On the reproduction of the diamond, by M. C. Friedel. Remarks by M. Berthelot (see article).-On the pathogeny of diabetes; part played by the expenditure and the production of glycose in the deviations of the glycemic function, by MM. A. Chauveau and Kaufmann. The same inferiority of venous with respect to arterial blood, as regards the amount of sugar contained in it, occurs in all the deviations of the glycemic function produced by a lesion of the central nervous system. This inferiority is equally pronounced in the hyperglycemia resulting from the extirpation of the pancreas.-On the progress of the art of surveying with the aid of photography, in Europe and America, by M. A. Lausedat. Since 1888 a zone of twenty miles on each side of the Canadian Pacific Railway, in the neighbourhood of the Canadian National Park, has been surveyed with the aid of photography under the direction of Messrs. Deville, Drewry, and McArthur, at an average rate of 1040 square km. per annum for four men under great climatic disadvantages. The cost of the undertaking amounts to three dollars per square km. -Determination of the amount of carbonic oxide which can be contained in confined air, by means of a bird employed as physiological reagent, by M. Ñ. Gréhant.-On the properties of faculæ ; reply to a note by Mr. G. Hale, by M. H. Deslandres. -The probability of coincidence between solar and terrestrial phenomena, by M. G. E. Hale.-Note on an explicit expression of the algebraic integral of a hyperelliptic system of the most general form, by M. F. de Salvert.-On a generalisation of Bertrand's curves, by M.Alphonse Dumoulin.-On the surfaces which admit a system of lines of spherical curvature and which have the same spherical representation for their lines of curvature, by M. Blutel.-On semicircular interference fringes, by M. G. Meslin. Rectilinear interference fringes are sections of hyperboloids by planes parallel to their axis, the light being propagated in a direction at right angles to that axis. If the light proceeds along the axis, a screen perpendicular to it will cut circular sections, and the fringes will have the form of a circumference of which a greater or smaller arc will be seen accordingly as the two pencils overlap more or less. In practice these circular fringes were obtained by separating two of Bellet's half lenses and placing them one before the other in front of a very small hole illuminated by sunlight, such that the axis of the pencil passes through the optical centre of the two lenses. Under these conditions two pencils are formed from the same source of light, which may be made to show circular fringes by moving the lenses slightly in a direction perpendicular to their optical axes.-Study of the fluorides of chromium, by M. C. Poulenc.-On a new soldering process for aluminium and various other metals, by M. J. Novel. For aluminium the following solders are recommended: (1) Pure tin, fuses at 250°. (2) Pure tin 1000 gr. ; lead 50 gr. (280° to 300°). (3) Pure tin 1000 gr. ; pu.e zinc 50 gr. (280°.0 320°). solders do not stain or attack aluminium. A nickel soldering bit is preferable. (4) Pure tin 1000 gr. ; red copper 10 to 15

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gr. (350° to 450°). (5) Pure tin 1000 gr.; pure nickel 10%. gr. (350° to 450°). These give a slightly yellowish tint, b very durable. (6) Pure tin 900 gr.; copper 100 gr.; bismerk : 3 gr. This is specially suitable for soldering aluminium ben - d Action of acetic acid and formic acid upon terebenthine, by Bouchardat and Oliviers.-On the mode of elimination carbonic oxide, by M. L. de Saint-Martin. Experimenti that animals partly intoxicated by carbonic oxide, wher in conditions under which natural elimination is impos destroy slowly but regularly a certain quantity of the pois gas, this destruction being the more active the less the ic tion. It is probably converted into carbon dioxide. The effect is entirely dependent upon the time during wh organism is exposed to the gas, and a very small quantity ca fatal on prolonged exposure.-Influence of pilocarpine and b zine on the production of sugar in milk, by M. Comevitthe seat of the colouring matter in the green oyster, b Joannes Chatin.-On pseudo-fertilisation in the Ur MM. P. A. Dangeard and Sapin-Trouffly,-On the subor formed by the nucleole in Spirogyra setiformis, and the d force which it exerts upon them at the moment of the of the cellular nucleus, by M. Ch. Decagny.-On a pross measuring the double refraction of crystalline plates. Georges Friedel.-A horizontal section of the French Ag M. W. Kilian.-On the arrangement of the cretaceous be the interior of the Aquitaine basin, and their relations to te formations, by M. Emmanuel Fallot.

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