The quantity was far too small to encourage a search for cobalt and other metals.

Besides the nickeliferous iron, which is disseminated very sparsely, and in particles singularly unequal in size and distribution, and with which troilite is associated in very small quantity, chromite is present as a constituent of small but appreciable amount. The crystals of this mineral are distinct and brilliant, and sometimes present good angles for measurement. One gave the solid angle of a regular octahedron.

The Manegaum Meteorite of 1843.-This meteorite fell at Manegaum, in Khandeish, India, on the 26th July, 1843. Only a small fragment was preserved, and of this a portion was given by the Asiatic Society of Bengal to the British Museum in 1862. In 1863 I described its appearance as seen in section in the microscope, and gave the parti culars of its fall (Phil. Mag., s. iv. p. 135, 1863).

From the minuteness of the specimen I had very little material to work upon. One mineral is conspicuous in the stone, namely, a primrose-coloured transparent crystalline silicate in small grains, loosely cemented by a white flocculent mineral. This greenish-yellow mineral (I.) and a fragment of the entire meteorite (II.) were analyzed, and crystalline grains of the former were measured on the goniometer. The prism angles (1) for the prism {1 1 0} were about and (2) for the prism {101} were 988; for {100, 110} about 46°; for {100, 101}, 49° 4′; and for {1 1 0, 1 0 1}, 58° 39′. The analyses gave the following numbers :

Silicic acid ...

81° 52'

88° 92°

53.629 23.32

Oxygen ratios. 28.602

}

14.305

1.495

The specific gravity of the granular mineral is 3198, and its hardness 5.5.

The result of the above analyses is to show that, except for a little chromite and a little augite, with possibly in the crystallized mineral a little free silica, both that mineral and the collective silicate of the stone consist of a ferriferous enstatite.

The formula most in accordance with the analysis would be

(Mg Fe) O, SiO2;

that of the enstatite in the Breitenbach meteorite is

( Mg Fe) O, SiO2.

The bulk of the Busti meteorite consists of a purely magnesian enstatite; this of Manegaum is almost entirely an enstatite richer in iron than any yet examined. Both bear evidence to the white flocculent mineral which characterizes the microscopic sections of many meteorites, being composed of this now important mineral enstatite.

In publishing the results I have obtained in the attempt, so far as this memoir goes, to treat exhaustively of the mineralogy of two important meteorites, I wish to record the obligations I am under to Dr. Flight, Assistant in my Department at the British Museum, for his valuable aid in the chemical portion of the inquiry.

"On Fluoride of Silver. Part I.," by George Gore, F.R.S.-This communication treats of the formation, preparation, analysis, composition, common physical properties, and chemical behaviour of fluoride of silver.

The salt was prepared by treating pure silver carbonate with an excess of pure aqueous hydrofluoric acid in a platinum dish, and evaporating to dryness, with certain precautions. The salt thus obtained invariably contains a small amount of free metallic silver, and generally also traces of water and of hydrofluoric acid, unless special precautions mentioned are observed. It was analyzed by various methods: the best method of determining the amount of fluorine in it consisted in evaporating to dryness a mixture of a known weight of the salt dissolved in water, with a slight excess of pure and perfectly caustic lime in a platinum bottle, and gently igniting the residue at an incipient red heat until it ceased to lose weight. By taking proper care, the

results obtained are accurate. The reaction in this method of analysis takes place according to the following equation, 2AgF+ CaO = CaF2+ 2Ag+0. Sixteen parts of oxygen expelled equal thirty-eight parts of fluorine present. One of the methods employed for determining the amount of silver consisted in passing dry ammonia over the salt in a platinum boat and tube at a low red heat. The results obtained in the various analyses establish the fact that pure fluoride of silver consists of nineteen parts of fluorine and 108 of silver.

"Approximate Determinations of the Heating Powers of Arcturus and a Lyræ," by E. T. Stone.-About twelve months ago, said the author, I began to make observations upon the heating-power of the stars. My first arrangements were simply these: I made use of a delicate reflecting astatic galvanometer, and a thermo-electric pile of nine elements. The pile was screwed into the tube of a negative eyepiece of the Greenwich Great Equatorial, from which the eye-lenses had been removed.

I soon convinced myself that the heat, condensed by the object-glass of 12 in. upon my pile, was appreciable in the case of several of tho brighter stars; but the endless changes in the zero-point of the galvanometer-needle, and the magnitude of these changes, compared with those arising from the heating-power of the stars, prevented me from making any attempts to estimate the absolute magnitude of the effects produced. Every change in the state of the sky, every formation or dissipation of cloud, completely drove the needle to the stops. At the February meeting of the Royal Astronomical Society I first became aware of what Mr. Huggins had done upon this question. His arrangements, however, did not appear to me to meet the difficulties which I had encountered. After some trials, I arranged my apparatus as follows, and with its present form I am satisfied.

I took two pairs of plates of compounds of antimony and bismuth. The areas are about (0.075)2 in., and their distance is about 0.25 in. The poles are joined over in opposite directions to the terminals of the pile and galvanometer. The whole pile is screwed into a tube of one of the negative eyepieces of the great equatorial. This completely shuts the pile up in the telescope-tube. A thick flannel bag is then wrapped over the eyepiece and terminals. The bag is prevented from actually touching the case of the pile, and is useful in preventing the irregular action of draughts upon the case of the pile and terminals. The wires are led from the terminals of the pile to the observatory library, where I have placed the reflecting galvanometer. This separation of the galvanometer from the telescope is most inconvenient, but it was absolutely necessary on account of the large moving masses of iron in the observing-room.

The two faces of the pile are so nearly alike, that the currents which are generated by an equal heating of them are exceedingly feeble. The telescope is first directed so that the star falls between the faces, and allowed to remain thus until the needle is nearly steady at the zero.

The star is then placed alternately upon the two faces, and the corresponding readings of the galvanometor taken as soon as the needle appears to have taken up its position, which usually takes place in about ten minutes. In order to avoid changes of zero, I have always reduced those readings by comparing a reading with star on the one face with the mean of two readings with star on the other, taken before and after the reading with star on the first, or vice versa. With this precaution I have never met with any anomalous results, although in making the observations I have usually joined over the terminals, without knowing the direction for heat, and have left this undetermined until the completion of the observations. I mention this because the differences in the readings for star on the one, which I call a, and star on the other, which I call ẞ, in the state in which I use my galvanometer are small.

On many nights, when very slight appearances of cloud prevailed, I have not been able to make any satisfactory observations at all. The number of divisions over which the spot of light travels on the galvanometer-scale for a given difference of temperature of the faces a and is of course dependent upon many circumstances, and especially upon the position of the sensitiveness-regulation magnet of the galvanometer.

I have thought it useless, therefore, to publish any results unless obtained upon nights when the state of the galvanometer was eliminated by referring to an independent source of heat. The way in which this has been attempted is as follows::

After obtaining the differences in the position of the spot of light on the galvanometer-scale for star on a and star on ß, I remove the pile from the telescope, leaving all its galvanic connections untouched, and mount the pile so that the two halves of the face of a Leslie's cube, containing boiling water, each radiates heat upon one face a or B of the pile, placed at a known distance of about twenty inches from the cube. After some time the deflection of the needle will fall nearly to zero, and become steady enough for observation. A piece of glass is then placed to intercept from ẞ a portion of the heat from one half of the face of the cube, and when the needle has taken up its position, the reading is taken. Next, the glass is placed to intercept a portion of the heat from the face a, and the galvanometer-reading

taken, as before, as soon as the needle has announced its position of rest.

Thursday, January 20th.-Dr. W. A. Miller, V.P., in the chair. The following paper was read:-" Freliminary Paper on Certain Drifting Motions of the Stars," by Richard A. Frector, B.A., F.R.A.S.; communicated by Warren De La Rue, V.P.R.S.

A careful examination of the proper motions of all the fixed stars in the catalogues published by Messrs. Main and Stone (Memoirs of the Royal Astronomical Society, vols. xxviii. and xxxiii.) has led me to a somewhat interesting result. I find that in parts of the heavens the stars exhibit a well-marked tendency to drift in a definite direction. In the catalogues of proper motions, owing to the way in which the stars are arranged, this tendency is masked; but when the proper motions are indicated in maps, by affixing to each star a small arrow whose length and direction indicate the magnitude and direction of the star's proper motion, the star-drift (as the phenomenon may be termed) becomes very evident.

It is worthy of notice that Mädler, having been led by certain considerations to examine the neighbourhood of the Pleiades for traces of a community of proper motion, founded on the drift he actually found in Taurus his well-known theory that Alcyore (the lucida of the Pleiades) is the common centre around which the sidereal system is moving. But in reality the community of motion in Taurus is only a single instance, and not the most striking that might be pointed out, of a characteristic which may be recognized in many regions of the heavens. In Gemini and Cancer there is a much more striking drift towards the south-east, the drift in Taurus being towards the southwest. In the constellation Leo there is also a well-marked drift, in this case towards Cancer.

These particular instances of star-drift are not the less remarkable, that they (the stars) are drifting almost exactly in the direction due to the proper motion which has been assigned to the sun; because the recent researches of the Astronomer Royal have abundantly proved that the apparent proper motions of the stars are not to be recognized as principally due to the sun's motion. Mr. Stone has shown even that we must assign to the stars a larger proper motion, on the average, than that which the sun possesses. Looking, therefore, on the stars as severally in motion, with velocities exceeding the sun's on the average, it cannot but be looked upon as highly significant that in any large region of the heavens there should be a community of motion such as I have described. We seem compelled to look upon the stars which exhibit such community of motion as forming a distinct system, the members of which are associated indeed with the galactic system, but are much more intimately related to each other.

In other parts of the heavens, however, there are instances of a star-drift opposed to the direction due to the solar motion. A remarkable instance may be recognized among the seven bright stars of Ursa Major. Of these, the stars ẞ, y, ô, ε, and %, are all drifting in the same direction, and almost exactly at the same rate, towards the "apex of the solar motion," that is, the point from which all the motions due to the sun's translation in space should be directed. If these five stars, indeed, form a system (and I can see no other reasonable explanation of so singular a community of motion), the mind is lost in contemplating the immensity of the periods which the revolutions of the components of the system must occupy. Mädler had already assigned to the revolution of Alcor around Mizar ( Ursa) a period of more than 7,000 years. But if these stars, which appear so close to the naked eye, have a period of such length, what must be the cyclic periods of stars which cover a range of several degrees upon the heavens.

In like manner the stars a, B, and y Arietis appear to form a single system, though the motion of a is not absolutely coincident either in magnitude or direction with that of ẞ and y, which are moving on absolutely parallel lines with equal velocity.

There are many other interesting cases of the same kind. I hope soon to be able to lay before the Society a pair of maps in which all the well-recognized proper motions in both hemispheres are exhibited on the stereographic projection. In the same maps also the effects due to the solar motion are exhibited by means of great circles through the apex of the solar motion, and small circles or parallels having that apex for a pole.

It appears to me that the star-drift I have described serves to explain several phenomena which had hitherto been thought very perplexing. In the first place, it accounts for the small effect which the correction due to the solar motion has been found to have in diminishing the sums of the squares of the stellar proper motions. Again, it explains the fact that many double stars which have a common proper motion, appear to have no motion of revolution around each other; for clearly two members of a drifting system might appear to form a close double, and yet be in reality far apart and travelling not around each other, but more closely around the centre of gravity of the much larger system they form part of.

I may add that, while mapping the proper motions of the stars, I have been led to notice that the rich cluster around x Persei falls almost exactly on the intersection of the Milky Way with the great

circle which may be termed the equator of the solar motion; that is, the great circle having the apex of the sun's motion as a pole. This circumstance points to that remarkable cluster, rather than to the Pleiades, as the centre of the sidereal system, if indeed that system have a centre cognizable by us. When we remember that for every fixed star in the Pleiades there are hundreds in the great cluster in Perseus, the latter will seem the worthier region to be the centre of motion. I should be disposed, however, to regard the cluster in Perseus as the centre of a portion of the sidereal system, rather than as the common centre of the Galaxy.

The peculiarities of the apparent proper motions of the stars seem to me to lend a new interest to the researches which Mr. Huggins is preparing to make into the stellar proper motions of recess or approach.

ROYAL INSTITUTION OF GREAT BRITAIN. FRIDAY, JANUARY 21ST.-Sir Henry Holland, president, in the chair. A most interesting lecture on Haze and Dust was delivered by Professor Tyndall. The president of the Institution was supported by the Right Hon. W. E. Gladstone, Earl Granville, the Dean of Westminster, Sir Edwin Landseer, Professor Huxley, Dr. Bence Jones, Mr. Gassiot, Mr. Warren De La Rue, and many other distinguished persons. Lady Augusta Stanley and a large assembly of ladies also graced the theatre with their presence. The Professor said Solar light in passing through a dark room reveals its track by illuminating the dust floating in the air. "The sun," says Daniel Culverwell,"discovers atomes, though they be invisible by candlelight, and makes them dance naked in his beams."

In my researches on the decomposition of vapours by light I was compelled to remove these "atomes" and this dust. It was essential that the space containing the vapours should embrace no visible thing; that no substance capable of scattering the light in the slightest sensible degree should, at the outset of an experiment, be found in the experimental tube" traversed by the luminous beam.

For a long time I was troubled by the appearance there of floating dust, which, though invisible to diffuse daylight, was at once revealed by a powerfully condensed beam. Two tubes were placed in succession in the path of the dust: the one containing fragments of glass wetted with concentrated sulphuric acid; the other, fragments of marble wetted with a strong solution of caustic potash. To my astonishment it passed through both. The air of the Royal Institution sent through these tubes at a rate sufficiently slow to dry it, and to remove its carbonic acid, carried into the experimental tube a considerable amount of mechanically suspended matter, which was illuminated when the beam passed through the tube. The effect was substantially the same when the air was permitted to bubble through the liquid acid and through the solution of potash.

Thus, on the 5th of October, 1868, successive charges of air were admitted through the potash and sulphuric acid into the exhausted experimental tube. Prior to the admission of the air the tube was optically empty; it contained nothing competent to scatter the light. After the air had entered the tube, the conical track of the electric beau was in all cases clearly revealed. This, indeed, was a daily observation at the time to which I now refer.

I tried to intercept this floating matter in various ways; and on the day just mentioned, prior to sending the air through the drying apparatus, I carefully permitted it to pass over the tip of a spirit-lamp flame. The floating matter no longer appeared, having been burnt up by the flame. It was therefore organic matter. When the air was sent too rapidly through the flame, a fine blue cloud was found in the experimental tube. This was the smoke of the organic particles. I was by no means prepared for this result; for I had thought, with the rest of the world, that the dust of our air was, in great part, inorganic and non-combustible.

Mr. Valentin had the kindness to procure for me a small gasfurnace, containing a platinum tube, which could be heated to vivid redness. The tube also contained a roll of platinum gauze, which, while it permitted the air to pass through it, insured the practical contact of the dust with the incandescent metal. The air of the laboratory was permitted to enter the experimental tube, sometimes through the cold, and sometimes through the heated tube of platinum. The rapidity of admission was also varied. In the first column of the following table the quantity of air operated on is expressed by the number of inches which the mercury gauge of the air-pump sank when the air entered. In the second column the condition of the platinum tube is mentioned, and in the third the state of the air which entered the experimental tube :

State of Platinum
Tube.
Cold...
Red-hot

Cold..

Red-hot Cold.....

State of Experimental
Tube.
Full of particles.
Optically empty.
Full of particles.
Optically empty.
Full of particles.
Optically empty.

cleansed by ordinary methods in air loaded with organic impurities, as we have proved our air to be. The instrument ought, in fact, to be made as hot as its temper will bear. But this is not done, and hence, notwithstanding all the surgeon's care inflammation often sets in after the first operation, rendering necessary a second and a third. Rapid putrefaction is found to accompany this new inflammation. The pus, moreover, which was sweet at first, and showed no trace of animal life, is now fetid, and swarming with active little organisms called vibrios. Professor Lister, from whose recent lecture this fact is derived, contends, with every show of reason, that this rapid putrefaction and this astounding development of animal life are due to the entry of germs into the abscess during the first operation, and their subsequent nurture and development under favourable conditions of food and temperature. The celebrated physiologist and physicist, Helmholtz, is attacked annually by hay-fever. From the 20th of May to the end of June he suffers from a catarrh of the upper air-passages; and he has found during this period, and at no other, that his nasal secretions are peopled by these vibrios. They appear to nestle by preference in the cavities and recesses of the nose, for a strong sneeze is necessary to dislodge them.

These statements sound uncomfortable; but by disclosing our enemy they enable us to fight him. When he clearly eyes his quarry the eagle's strength is doubled, and his swoop his rendered sure. If the germ theory be proved true, it will give a definiteness to our efforts to stamp out disease which they could not previously possess. And it is only by definite effort under its guidance that its truth or falsehood can be established. It is difficult for an outsider like myself to read without sympathetic emotion such papers as those of Dr. Budd, of Bristol, on cholera, scarlet-fever, and small-pox. He is a man of strong imagination, and may occasionally take a flight beyond his facts; but without this dynamic heat of heart the stolid inertia of the free-born Briton cannot be overcome. And as long as the heat is employed to warm up the truth without singeing it over-much; as long as this enthusiasm can overmatch its mistakes by unequivocal examples of success, so long am I disposed to give it a fair field to work in, and to wish it God speed.

But let us return to our dust. It is needless to remark that it cannot be blown away by an ordinary bellows; or, more correctly, the place of the particles blown away is in this case supplied by others ejected from the bellows, so that the track of the beam remains un. impaired. But if the nozzle of a good bellows be filled with cotton wool not too tightly packed, the air urged through the wool is filtered of its floating matter, and it then forms a clean band of darkness in the illuminated dust. This was the filter used by Schroeder in his experiments on spontaneous generation, and turned subsequently to account in the excellent researches of Pasteur. Since 1868 I have constantly employed it myself.

But by far the most interesting and important illustration of this filtering process is furnished by the human breath. I fill my lungs with ordinary air and breathe through a glass tube across the electric beam. The condensation of the aqueous vapour of the breath is shown by the formation of a luminous white cloud of delicate texture. It is necessary to abolish this cloud, and this may be done by drying the breath previous to its entering into the beam; or, still more simply, by warming the glass tube. When this is done the luminous track of the beam is for a time uninterrupted. The breath impresses upon the floating matter a transverse motion, but the dust from the lungs makes good the particles displaced. But after some time an obscure disk appears upon the beam, the darkness of which increases, until finally, towards the end of the expiration, the beam is, as it were, pierced by an intensely black hole, in which no particles whatever can be discerned. The air, in fact, has so lodged its dirt within the lungs as to render the last portions of the expired breath absolutely free from suspended matter. This experiment may be repeated any number of times with the same result. It renders the distribution of the dirt within the lungs as manifest as if the chest were transparent.

I now empty my lungs as perfectly as possible, and placing a handful of cotton wool against my mouth and nostrils, inhale through it. There is no difficulty in thus filling the lungs with air. On expiring this air through the glass tube, its freedom from floating matter is at once manifest. From the very beginning of the act of expiration the beam is pierced by a black aperture. The first puff from the lungs abolishes the illuminated dust and puts a patch of darkness in its place; and the darkness continues throughout the entire course of the expiration. When the tube is placed below the beam and moved to and fro, the same smoke-like appearance as that obtained with a flame is observed. In short, the cotton wool, when used in sufficient quantity, completely intercepts the floating matter on its way to the lungs.

And here we have revealed to us the true philosophy of a practice followed by medical men, more from instinct than from actual knowledge. In a contagious atmosphere the physician places a handkerchief to his mouth and inhales through it. In doing so he unconsciously holds back the dirt and germs of the air. If the poison were a gas it

[Jan. 26, 1870.

would not be thus intercepted. On showing this experiment with the cotton wool to Dr. Bence Jones, he immediately repeated it with a silk handkerchief. The result was substantially the same, though, as might be expected, the wool is by far the surest filter. The applica tion of these experiments is obvious. If a physician wishes to hold back from the lungs of his patient, or from his own, the germs by which contagious disease is said to be propagated, he will employ a cotton wool respirator. After the revelations of this evening such respirators must, I think, come into general use as a defence against contagion. In the crowded dwellings of the London poor, where the isolation of the sick is difficult, if not impossible, the noxious air around the patient may, by this simple means, be restored to practical purity. Thus filtered, attendants may breathe the air unharmed. In all probability the protection of the lungs will be the protection of the entire system. For it is exceedingly probable that the germs which lodge in the air-passages, and which, at their leisure, can work their way across the mucous membrane, are those which sow in the body epidemic disease. If this be so, then disease can certainly be warded off by filters of cotton wool. I should be most willing to test their efficacy in my own person. And time will decide whether in lung diseases also the woollen respirator cannot abate irritation, if not arrest decay. By its means, so far as the germs are concerned, the air of the highest Alps may be brought into the chamber of the invalid. The lecture was illustrated by a series of chemical experiments, and there was great applause manifested during its delivery and at the close.

ZOOLOGICAL SOCIETY OF LONDON.

JANUARY 13TH.-John Gould, Esq., F.R.S., V.P., in the chair. The secretary called attention to certain additions to the society's menagerie during November and December last, amongst which was particularly noticed a rare American monkey (Pithecia ouakari) from the Rio Negro, deposited by L. Joel, Esq., C.M.Z.S.

A letter was read from Lord Lilford, F.Z.S., relating to the exact locality of a specimen of Otus capensis, lately living in the society's gardens.

A letter was read from Dr. A. Ernst, of Caraccas, C.M.Z.S., containing some notes on animals recently obtained in the vicinity of that city.

The Rev. H. B. Tristram, F.R.S., exhibited a pair of Tawny Eagles, (Aquila navioides) obtained near Etawah, N.W. India, by Mr. W. G. Brooks, C.E., being the first authentic examples of this species recognized from that country.

Mr. Swinhoe exhibited and made remarks on some skins of tigers and leopards from various parts of China.

Mr. Gould exhibited a new and very remarkable pigeon, supposed to be from New Guinea, which he had recently described under the name Otidiphaps nobilis.

A communication was read from Mr. Henry Adams containing descriptions of a new genus, and of eighteen new species of land and marine shells from the Red Sea, Hainan, and other localities.

A communication was read from Dr. Cobbold containing the description of a new generic type of Entozoa, discovered in a specimen of the Aard-Wolf (Proteles cristatus), which had recently died in the menagerie. To this were added remarks on the affinities of this Entozoon, especially in reference to the question of parthenogenesis. A communication was read from Mr. Morton Allport, F.Z.S., containing a brief history of the introduction of the salmon (Salmo salar) and other Salmonidæ to the waters of Tasmania.

Dr. Murie read a paper containing additional memoranda on irregularity in the growth of salmon. Dr. Murie's observations were founded principally upon specimens hatched and reared in the society's fishhouse.

ANTHROPOLOGICAL SOCIETY OF LONDON.

ANNUAL GENERAL MEETING, JAN. 18TH.-John Beddoe, Esq., M.D., president, in the chair. The report of auditors showed the income of the society in 1869 to have been £1,091. 9s. 5d., the expenditure £964. 9s. 8d., and the balance in hand on the 31st Dec., £126. 19s. 9d. The report of council was read and adopted. The president then delivered the annual address, including a full obituary notice of Dr. James Hunt, founder of the society. The ballot for the election of officers and council to serve in 1870 was taken with the following result:-President, John Beddoe, Esq., M.D.; Vice-presidents, H. Beigel, Esq., M.D., Captain R. F. Burton, Dr. Charnock, J. Barnard Davis, Esq., M.D., F.R.S., Captain Bedford Pim, R.N., Dr. Berthold Seemann; Director, Thos. Bendyshe, Esq., M.A.; Treasurer, Rev. Dunbar I. Heath, M.A., Council, J. Gould Avery, Esq., J. Burford Carlill, Esq., M.D., S. E. Collingwood, Esq., Walter C. Dendy, Esq.; George Harris, Esq., Jonathan Hutchinson, Esq., W. B. Kesteven, Esq.; Kelburne King, Esq., M.D., Richard King, Esq., M.D., A. L. Lewis, Esq., St. Geo. J. Mivart, Esq., F.R.S., Major

Jan. 26, 1870.]

S. R. I. Owen, C. Robert Des Ruffières, Esq., John Thurnam, Esq., M.D., Edward Peacock, Esq., F.S.A., J. Spence Ramskill, Esq., M.D., W. S. W. Vaux, Esq., F.R.S., C. Staniland Wake, Esq., Alfred Wiltshire, Esq., M.D., and E. Villin, Esq.

MATHEMATICAL SOCIETY.

JANUARY 13TH.-Professor Cayley, president, in the chair. Dr. Ramsay was proposed for election. Mr. Walker gave an account of his paper "On Equations of Centres and Foci, and conditions of certain Involutions." Dr. Henrici, Professor Hirst, Mr. Clifford, and the president, took part in a discussion on the subject. The president then made a statement of some results he had arrived at with reference to Quartic surfaces. Mr. Roberts exhibited and explained some diagrams of the pedals of conic sections which he had constructed by the methods described in his communication of January 14th, 1869.

STATISTICAL SOCIETY.

THE third ordinary meeting of the present session was held on Tuesday last, the 18th of January, William Newmarch, Esq., F.R.S., president, in the chair. The following gentlemen were elected fellows:-Messrs. Iltudus Thomas Prichard, Henry Hoare, David Maclagan, and Josiah Samuel Parker. Professor Lee read a paper on "The Statistics of Joint-Stock Companies from 1814 to the present time, and of Companies with Limited and Unlimited Liability formed since the year 1856."

THE INSTITUTION OF CIVIL ENGINEERS.

Ar the meeting of this society on Tuesday, the 11th inst., Mr. Charles B. Vignoles, F.R.S., president, in the chair, five candidates were balloted for and declared to be duly elected,-viz., Mr. Alfred Andrew Langley, engineer and manager to the Hereford, Hay, and Brecon Railway; Mr. Robert White, first-class engineer upon the Great Southern of India Railway; and Mr. Edmund Wragge, chief engineer of the Toronto, Grey, and Bruce, and the Toronto and Nipissing Railways, in Canada, as members; and Mr. William Rawlinson, engineer and manager of the Brazilian Street Railway Company, and Mr. Charles Willman, Middlesbrough, as associates.

MANCHESTER LITERARY AND PHILOSOPHICAL SOCIETY. ORDINARY MEETING, DEC. 28TH, 1869.-J. P. Joule, LL.D., F.R.S., &c., president, in the chair. "On Pollen; considered as an Aid in the Differentiation of Species," by Charles Bailey, Esq.-Having recently examined the pollen of several thousand species of plants, I am led to think that the characters presented by these grains might prove useful as a means of differentiation in allied species; my researches, however, have not been sufficiently extensive to form any positive conclusions, but as leisure permits I hope to prosecute the subject further. In the meanwhile the following notes are thrown out as indications of some of the more noticeable distinctions to be drawn from a careful comparison of these organs, and they may serve to draw the attention of others to the matter.

There are four points, in one or other of which pollen grains of plants belonging to the same genus may be found to differ from each other, viz., form, markings, dimensions, and colour.

1. Form.-It has long been noticed that certain types of pollen are characteristic of the natural order to which the plants which produce them belong, as, for instance, the peculiar pitted polyhedral pollen of the Caryophyllaceae, the spherical spiny pollen of the Malvacea, the large triangular pollen of the Onagracea, the peculiar pollen of the Coniferæ, or the elliptical pollen of the Liliaces and other monocotyledonous orders; in fact, most orders possess a type sufficiently marked to be characteristic of each. This statement, however, must be accepted with limitations; the Compositæ, for instance, have three or more well-marked types, represented by the beautifully sculptured pollen of the Chicory, the minute oval spiny pollen of the Asters, Calendulas, Cacalias, &c., and another form wholly destitute of spines as in the Centaurea Scabiosa. There are, besides, other natural orders where similar variety occurs.

But differences of form are met with in plants of the same genus, by which the one species or the other is readily marked off by its pollen; thus the pollen grain of Anemone sulphurea is roundish, but that of Anemone montana is elliptic; the pollen of Aronicum Doronicum is much more elongate than that of A. Scorpioides; and while the grains of Ranunculus philonotis are round and yellow, those of R. platanifolius are elliptic, white and smaller.

2. Markings. Here again there is endless diversity, and a boundless field lies open for the researches of tired-out dot-and-line hunters

of diatom-valves. A few instances only of the more striking differences can be given here.

The pollen of the Geraniacea and Campanulaceae is for the most part globular, but while some of the grains are quite smooth others are covered with spines; thus the pollen of Campanula Media has a number of short spines sparsely scattered over the surface of the grain, but C. ranunculoides is wholly destitute of them. In other plants these spines are replaced by tubercles, and both spines and tubercles vary greatly in length and number; for example, in Valeriana tuberosa the spines are only half the length of those on the pollen of V. montana, the grains being also slightly smaller. The pollen of the Liliacea is often covered with a more or less prominent reticulation, which is subject to much variation; compare, for example, the coarse network which invests the pollen of Lilium croceum with the finer reticulation of L. canadense, the grains of the latter species being much more globose and smaller.

3. Dimensions.-Some instances of the differences observable in the size of pollen grains have already been published by Professor Gulliver, whose measurements of the pollen of various species of Ranunculus show the help that may be derived from this character; R. arvensis is nearly twice the size of R. hirsutus, their dimensions being respectively and of an inch.

I have not had the time to make similar careful measurements with the micrometer, but I have seen sufficient to be satisfied that while there is considerable variation in dimensions between the pollen of one species and that of another, they are tolerably constant in size in the same species.

For some noticeable differences compare the smaller pollen of Epilobium brachycarpum with the larger pollen of E. Fleischeri or that of Senecio gallicus with S. incanus, the spines on the latter species being also much coarser. Again, the pollen of Silene acaulis is but half the size of that of S. alpina, the latter having some beautiful markings in addition; the pollen grains of this genus differ from the usual caryophyllaceous type in not having the pits or depressions common in the order, so that the grains become spherical rather than polyhedral.

4. Colour. This is not so reliable a character for differentiation as the others noticed, since species differ amongst each other according to the soil, &c., of the place where they have grown. I remember gathering some years ago, near Ashbourne, Derbyshire, a variety of Stellaria Holostea having a dark purple pollen instead of the ordinary pale yellow. An example or two under this head will suffice.

The pollen of Ajuga genevensis is yellow, but that of A. pyramidalis is usually white; again, while the grains of Ornithogalum umbel latum are large and yellow, those of O. nutans are small and white.

Some objection may be raised to any reliance being placed upon the dry shrivelled-up grains of herbaria specimens-such specimens being in most cases the only ones obtainable for purposes of investigation; but the structure of pollen is such as to bring into greater prominence the pores, folds, valves, and other markings which are met with on their surface after the grains have collapsed by the discharge of their contents.

In regard to the mounting of these objects for the microscope, they show to the best advantage when put up perfectly dry; the cells should be sufficiently shallow to admit of no more than a single layer, and at the same time deep enough to permit the grains to move about. If pollen is mounted soon after it has been discharged from the fresh anthers the fovilla is apt to condense on the covering glass, and the slide soon becomes useless. The stamens taken from an unopened flower-bud furnish the best and cleanest pollen, and these should be selected in preference to those taken from the fully developed flower. Canada balsam, glycerine, and other media are occasionally helpful in making out structure; thus the pores of Campanula rotundifolia, Phyteuma halleri, and other allied speies are made much more distinct when mounted in balsam.

A large series of slides illustrative of the above remarks was exhibited at the meeting.

MICROSCOPICAL AND NATURAL HISTORY SECTION.

December 6th, 1869.-John Watson, Esq., president of the section, in the chair. Mr. W. Boyd Dawkins, M.A., F.R.S., was elected a member of the section.

Mr. J. B. Dancer, F.R.A.S., read a short paper on some of the new hydrocarbon compounds from which he had obtained very beautiful polarizing objects for the microscope. These were exhibited to the members, and a more detailed account promised when the experiments are complete.

BRISTOL MICROSCOPICAL SOCIETY.

JANUARY 19TH.-Mr. W. J. Fedden, president, in the chair. The minutes of the last meeting having been read and confirmed, it was announced that Mr. Roper, honorary secretary, Royal Microscopical