[page] 410

SCIENTIFIC OPINION.

[May 4, 1870.

Undirqround Temperature.

Sib,—I inclose 1117 usual report of my 2 ft. below Burfaco thermometer.

If y<?a refer to my last month's (Maroh) report yon will see on the 18th the mercury rose two degrees, on that day there was an earthquake in St. John's, New Branswiok ; a fall of rook in a Cornish mine (a very unusual thing); and a loss of a ship on the ooast of France, when the captain thought he was on the English coast, and upon trial, by the Board of Trade, he was acquitted. Doubtless those who sat in judgment on him thought he was not to blame.

Did an earthquake cause a variation in his compasses ?

1870.

April 5....................................42°

8....................................42°

1 0....................................44°

1 1....................................45°

1 2....................................46°

IS....................................47°

17.........................48°

19....................................47°

26....................................49°

30....................................51°

Havant, May 2.

April 1 and 2 .

3 to 5..........

6 to 10 .......

41°

1 1.................. 42°

12 to 14 ......... 43°

15 and 16......... 44°

1 7.................. 45°-

18 to 21 ......... 46°

22 and 23......... 47°

24 to 28 ......... 48°

29 and 30......... 47°

C. J. R.

SCIENTIFIC SOCIETIES.

Secretaries of Societies will oblige at by regularly forwarding "Abstracts ol Proceedings;" and they would do much to enhance the interest and success of their meetings if they would enable us-to publish in anticipation "notices of papers to be read." _____

EOYAL SOCIETY.

Thursday. April 28th.—The following papers were read:—" On the Organs of Visum in IB* Common Mole," by Robert James Lee ; communicated by Samuel Solly, F.R.S.—The eye of the common mole and the structures connected with it undergo some remarkable changes during the growth of the animal. The gentleman Who does me the honour to present the results of an investigation into that subject to the Royal Society was desirous that it should be undertaken in order to ascertain the cause of the anomalous condition in which the organ of vision is found in the adult mole.

It was the suggestion of Mr. Solly that an examination of the eye of the young or foetal mole might assist in the explanation; for Mr. Solly had reflected much on the subject, and entertained reasons for believing that such an inquiry would be attended with a satisfactory result.

It is known that there is distinct evidence of the existence of an eye and other parts concerned in the endowment of sight in many of the various species of the mole genus. To what extent, however, the defective state of the organs permit of sight, or whether the animal is totally blind, are questions still undecided.

That the organ of vision in the young mole-would be found in a more • perfect state than in mature age was what Mr. Solly anticipated, while he conjectured, for physiological reasons, that the cause of the difference between them would be found to be a process of atrophy or degeneration in the various structures essential for the enjoyment of sight.

The specimens sent me for the purpose of examination consisted of a female mole, which appeared from its dimensions to have attained the full period of development, if it had not somewhat exceeded it, and of six unborn young about 1J in. long, and, as far as I could judge, beyond the middle of the period of gestation.

Before entering into anatomical details, I venture to review briefly the researches which have been made by anatomists into the subject. A summary of the views entertained by those who preceded him is given by Gottfried Treviranus, in his work published in 1820, " FVr-snischte Schriflen anatoitischen und physiologiscken InhalU, in the chapter on the Nerve* of Sense in Mammalian Animals. From this account it appears that it was Zinn who first described an optic nerve in the mole, and declared it to be a branch of that division of the fifth pair of nerves which is distributed to the noee.

The description by Zinn was published in the fourth volume of the Commentaries of the Royal Society of Gottenburg. " The optic nerve he says, " is long and of considerable tenuity. Its origin is the same as that of the very large nerve which passes to the proboscis. It takes a long obHqoe cour^ lying above the muscles of the nose, and passing

is finally inserted into the posterior part of the globe of the eye in the lnie of the axis of vision."

In 1813 Yon Tiedemann published a description ol the optic nerve

and the fifth pair, which differed in a very important respect from the account given by Zinn; for he says that although the optio nerves are small and difficult to distinguish, yet they exist as separate nerves, and present the same general character as in most of the mammalia. Tiedemann carried his investigations still further, and declared the absence of the third, fourth, and sixth pairs of nerves. He described certain filaments, whioh he stated to bo unconnected with the optic nerve, and to be similar to those branohes which are found in the tissues around the eye in other animals. The absenoe of the third, fourth, and sixth pairs of nerves was subsequently asserted also by Carus; but his account of the origin and termination of the optio nerves is not quite intelligible to mo. It appears, however, that the conclusions of Treviranus and Carus agreed that there was some connection between the optio nerve and the fifth, which sufficed to supply the mole to a certain degree with the sense of sight. Indeed, the chief physiological fact which Treviranus endeavoured to establish in the chapter of the work alluded to, was that the nerves of ono particular and special sense wore capable, under certain circumstances, of becoming endowed with the properties of nerves of another and different sense. " The fifth pair of nerves in some mammalia supply the place of the most important nerve of sense " is the introductory sentence in the chapter ; or, in other words, that a nerve of touch and feeling may become a nerve of sight, that is, sensitive to the rays of light; and he concludes the chapter thus:—" I cannot but agree with Carus that the optic nerve and the fifth branch enter into connection in the eye to produce the retina." This opinion met with opposition from Prof. Müller, who controverted it by the statement that true optio nerves had been exhibited to him by Dr. Henle (Baly's translation, p. 842).

From a remark of M. P. G. Pelletan, in his MSmoires sur la Socialite des Nerx'cs des Senses, quoted by Mr. Solly in his work on the Brain, it would appear that that anatomist had made a very careful examination of the organs of vision, both in the adult and foetal mole, for he " recommends the disseotion of either foetal moles or very young ones in whom the optic foramen is still distinct." The importanoe of this remark consists in the proof that Pelletan had observed that the optio foramina undergo somechange subsequent to the birth of the animal.

Yon Siebold has published the results of investigations into the difference between the eyes of certain species of Talpa. " The eyes are rudimentary," he says, "in the mole and Spalam typhhts, whioh live underground r and above all in Talpc. rrreo a-* the Chrysoohlores are the eyes rudimentary. They are a little more developed in the Musaraignes and the common mole. According to Ollivier (Bulletin de la SociStt Philomathique, vol. ii. No. 38, p. 105), all the ordinary elements of the eye are found in Spalax typhlus."

Leydig, in his Handbuch der Histologic, has some important remarks on the eyes of blind animals, and has described, in Muller's Archives, 1854, p. 346, the ceHular structure of the lens of the mole's eye, as presenting the character of embryonic structure, from which he concludes that the lens remains in its primitive embryonio condition.

Mr. Solly's investigations were directed to the state of the optic commissures at the base of the brain. "In the mole," he says, "in which the optic nerves are so extremely minute that they have often escaped detection, and by many authors described as entirely wanting, these commissural fibres are found distinctly crossing the base of the skull opposite the usual situation of the optio oommissure ; while the small black speck, evidently the rudiment of the eye, is supplied by a minttte branch from the fifth pair" (p. 289, op. cit.).

In Professor Owen's work on the Conqjanrfipe Anatomy and Phv-siology of Vertebrates (vol. ir. p. 246), the organ of sight, like that of smell, * stated to be " wanting in a few mammals, the eyeball being reduced to the sixe and oondition of the ocellus in Amblyopsis, and to its simple primitive offioe of taking cognixanoe of light, a filament of the fifth aiding a remnant of the proper optio nerve. The moles, especially the Italian kind, Talpa ctvca, and mole-rats exemplify this condition, in which, as in Spa la* typhlus, the skin passes over the ocellus without any palpebral opening or loss of hair."

Mr. Herbert Mayo has given a similar description in his Physiology, and has supplemented it by a drawing, in which the fifth nerve is represented as sending a filament directly to the globe of th^ eye.

From the above enumeration of the views entertained by anatomists regarding the eye and optio nerve of the mole, it is apparent that attention has been directed by some to the eye in particular, and to the structures intimately oonnected with it, while others have arrived at their conclusions from examination of the interior of the skull and the optic region of the brain.

It remained, therefore, to asoertain the condition of the optic nerve in the posterior part of the orbit, especially that portion of the nerve which lies in the optio foramen, and thus endeavour to connect the appearances described in the eye with those observed at the bass of the brain.

It is proposed to give an aoooont of the dissection of the full-grown mole, in order to oontrast the state of th« eye, the optio nerve, and the cranium, with that whioh those parte present in the fertal mole;

[page break]

May 4, 1870.]

SCIENTIFIC OPINION.

409

CORRESPONDENCE.

It is distinctly to be borne in mind that we do not, by inserting letters, convey sny opinion favourable to their conteoU. We open our columns to all, without leaning to any; and thus supply a channel for the publication of opinions of all shades.

No notice whatever will be taken of anonymous communications. We cannot undertake to return rejected communications.

The Controversy respecting the Action of Metallic Sodium on Acetic Ether.—From Professor J. A. Wankltn.

Sir,—The list of chemists who find thai the alkali-metals do not disengage hydrogen when they act upph acetic ether now includes Lowig and Weidmann, whose experimentsVere published in the year 1840; myself, who published results in 1868, and reiterated them in 1870 ; and Ladenburg, whose work on the subjeot has just appeared in the journal of tho Chemical Society of Berlin, date 1870.

The chemists who have found the contrary are—Genther, and his pupil Greiner, whose conjoint work bears the date 1864 ; and Frank-land and Duppa, whose conjoint work was published in the Philosophical Transactions in 1866, and who have again, in February, 1870, reiterated their statement before a meeting of the Royal Society, and published it in the Pnceedings of that learned body.

Questions in science are not decided either by counting hands or by weight of authority, but by quite different methods ; and though the number of chemists who have affirmed the evolution of hydrogen equals those who have denied it, and despite of the great weight of the authority that has most persistently asserted the evolution of hydrogen, tho question is now deoided—henceforth our text-books of chemistry will teach that there is no evolution of hydrogen when alkali-metals act on acetic ether.

Happily, the long controversy just conoluded is without many parallels in the history of chemistry, or indeed of science generally. Conflicts of chemical theory there have been—the antiphlogistic theory fought the theory of phlogiston; the theory of compound radials fought the theory of substitution; there was the controversy respecting the atomic weight of oxygen, whether it be eight or sixteen ; and many other questions of theory have for a time divided the ohe-mical world. Errors of observation or of experiment have likewise beatf made, and corrected by those that made them or by later ob-severs. But it is, happily, a thing quite unprecedented in the history of our science, for a chemist who has made an error to persist in it after it has been corrected and the sources of error explained. In order that chemists may form an adequate notion of the extraordinary character of Dr. Frankland's recent reply to me, I will quote from my paper (date March, 1869, Phil. Mag., vol. xxxvii. p. 179) :—

" Owing to the occurrence of this reaotion at 100° C." (t.«., the reaction by which alcohol and acetate of ethylene-sodium are produced from ethylate of sodium and acetic ether), " the attempts made by various chemists to render acetic ether free from any alcohol with which it might be contaminated by distilling it off sodium, have had the reverse result; and, continually producing alcohol, have rendered the ether more impure. By the action of sodium on acetic other there is produced sodium-triacetyle and hydrated oxide of ethylene-sodium, which latter attacks excess of acetic ether slowly at water-bath temperatures. A sample of acetic ether, which, from the mode of its preparation, must have been originally almost, if not quite, free from ' alcohol, became, after several distillations off a 6mall quantity of I metallic sodium, charged with alcohol to the extent of 15 per cent, i This circumstance, which really no one can be blamed for not expecting j and providing against, has probably led Genther, Frankland, and t Duppa astray."

What, however, shall we think when afterwards Dr. Frankland gpes before the Royal Society and describes the results given by acetic j ether which had been digested with arid distilled off sodium-amalgam ; as results given by alcohol-free acetic ether P

The controversy has been remarkable in many ways. It is notori-ous (and I think I need not particularly allude to events which are, I believe, not unknown to many chemists, at any rate in this country) ' that other weapons besides those that are legitimate weapons in con- j troversy have been employed against me. For example, in 1868, during the course of the water-controversy and the earlier stages of j the ether-controversy, I received a message from a Fellow of the | Royal Society, high in office and in influence, that "if I had treated Frankland better, I should have been elected a Fellow of the Society j as a matter of course."

•This message is an epitome of the actual relation of our Royal Society to those who are independently and fearlessly seeking the truth.

Chemistry will be extinct among us when chemists cease to be ready to undergo persecution for the advancement of the science ; but chemistry cannot flourish, and does not flourish, in England, where, as at the present time, the maintaining of chemical truth is the abandonment of a chemist's career. I am, Sir. yours, Ac.,

London, April. J. A. Wanxltn.

ON YELOCIPEDE8TRIANI8M.

Sir,—It would be Hampdenism to deny that different people require different quantities of bodily exercise, specially when such a truism is Btated by a medical man ; nor would it become me to criticise Mr. Barkas's very elaborate exposition of the muscles called into play by I bioyolism—it is a shorter word than velocipedestrianism. I do not, however, think it probable that the bioycling public will troublo medical advisers to any great extent before entering upon a favourite amusement, whether that be bicycling, skating, hunting, sliding, or rackets. We are unwise ; a medical adviser should be at the door of caoh English home, and be ready to convert out-goers into in-goers, or vice versd, according to the state of their "respiratory and circulatory systems."

But will you allow me to hesitate before putting much confidence in Mr. Barkas's knowledge of the action and use of mechanical apparatus ? This, as well as his experience, -must be small, since he confidently assumes that bicycles " are not of the slightest advantage for making long journeys.'' Will he kindly define what he means by long journeys ? All practised bicyclists, not amateurs, hold a very different opinion; and does not Mr. Barkas contradict himself strangely when he says that "the feeling of want of power gradually disappears as the rider becomes more and more profioient in the exercise " ? Any one who has studied the mere elements of mechanics, and has thought over the processes of walking and bioycling, will easily understand how a man can pass over a given distance in much less time and with much less fatigue, by means of the bicycle, than if he were walking; unless, indeed, the ground chosen is unfairly uphill. I will not encroach upon your valuable space by entering minutely into such Bimple matters, which are not purely scientific. Permit me, in one sentence, to apologize for proceeding thus far, and to impress upon your readers that bicycling is good for the health, as rowing is, and is likewise good for long journeys, except over hilly country. They need not trouble about medical advisers, if they remember that toleration in all things should be practised, and that over-fatigue, however occasioned, is disagreeable. Who will say that bicyoling is a more violent exercise than running to catch an obstinately-punctual last midnight train? In such a very possible case as this, Mr. Barkas would have the unfortunate traveller stop to be " assured that his respiratory and circulatory systems were in good order by his medical advisers." Would Mr. Barkas P Z am, <fcc.,----

April 30. iJicyclist.

The Weather of March, 1870.—From the Rev. F. B. Falkner.

Sir,—I beg to send you a few particulars of the weather of last month, as deduced from observations conducted by myself in this neighbourhood. The circumstances of atmospheric temperature and moisture refer to a stratum of air 4 ft. from the ground. The barometer is 335 ft. above sea-level. The solar thermometer has its bulb blackened and inolosed in a vacuum glass chamber, and is 34 ft. from the ground. Another thermometer is freely exposed to the sky, and indicates the lowest temperature to which unsheltered vegetation near the earth's surface is subjected in the course of the night.

General Results.

Mean maximum temperature of air.................................... 46-2*

Mean minimum temperature of air' ................................. 32-6°

Mean diurnal range of temperature of air........................... 13 6°

Highest temperature of air, on the 31st ........................... 56 "0*

Lowest temperature of air, on the 14th.............................. 20.4°

Total range of temperature of air .................................... 35 6°

Mean temperature of the air .......................................... 39-3°

Mean temperature of the dew-point ................................. 35^-2*

Highest 9 a.m. reading of the dew-point, on the 17th....... 50 0*

Lowest 9 a.m. reading of the dew-point, on the 12th ............ 23-0°

Highest reading of " solar " thermometer, on the 31st ......... 971°

Lowest temperature of unsheltered vegetation, on the 14th ... 10 0°

Mean weight of water-in a cubic foot of air........................2*3grs.

Rainfall .................................................................. 1440 in.

Mean height of the barometer......_v............................ 29 73Q in.

Total range of the barometer ...................................... 0-940 in.

Mean humidity of the air................................................... -86

In the lower regions of the atmosphere, northerly winds blew more frequently than southerly, in the ratio ef 7 to 2 ; and easterly winds prevailed over westerly in the ratio of 5 to 4. There were 16 frosty nights, and two days were frosty at 9 a.m. The temperature of the air fell below 25 degrees on 5 nights. On the other hand, it rose above 50 degrees on 8 days, and above 55 degrees on 2 days. The 9 a.m. reading of the barometer was above 30 in. on 9 days, and below 291 in. on 8 days. The rainfall for the three months, January, February, and March, 1870, amounted only to 4'31in.

I remain, Sir, your obedient servant,

F. B. Falkner.

Appleby Grammar School, Leicestershire, April 26.

[page] 411

following such an arrangement of the facts that the important, points of difference shall be apparent without separate comparison.

The eye of the common mole presents the appearance of a minute black and shining bead, closely attached to the skin of the head, and ooncealed by the hair so completely that it is difficult sometimes to discover it. In removing the skin the small globe is easily detaohed at the same time, find no indioation remains of the exaot position in which it was situated. This shows that in the mole the cavity of the I orbit is wanting, and that the structures usually found in the vicinity of the eye are in a different condition from that which they present in other mammalia. It is necessary, therefore, to divide the Bkin around thebaso of the eye in order to preserve the connection between the globe and the subjacent tissues.

Beneath the eye, and forming a basis on which it rests, is a firm mass of cellular fibrous tissue which assumes on disseotion a fusiform shape, with an attenuated portion passing towards the base of the skull. The filament becomes so exceedingly delicate in the deeper part of the orbit, that the difficulty of ascertaining its precise condition is probably the reason of the difference of opinion on the subject.

In Mr. Solly's specimen there was found to be no attachment whatever of the filament to the base of the skull; but in a former disseotion of a smaller, and probably younger speoimen, the continuity between the bone and the tissue was evident.

The filament of tissue above desoribed, and the connection whioh it formed between the eye and the skull, indaoed me to examine it microscopically, in order to ascertain whether it contained nervous fibres, or possessed any of the characters of the optic nerve.

It exhibited a tendency to divide in a longitudinal direction when I needles were applied to it, and presented the appearanoe of oellular j tissue, without, however, any trace of nerve-fibre. It will be seen, j nevertheless, from the description of the optio nerve in the total mole, that this delicate thread is the only vestige whioh remains of that important part of the organs of vision in the full-grown mole.

With regard to some minute branches of nerves and blood-vessels which pass into the tissue forming the base of the eye, both on its outer and inner side, it is not in my power to say definitely from whence they come, as their minute size prevented me from tracing them in the deeper part of the orbit to their points of exit from the skull.

j The eye of the full-grown mole presents a surface uniformly black and glistening, in whioh there is no indioation of a cornea and sclerotic distinct from one another, nor any evidence of an iris or pupillary aperture. Within the globe, when ruptured with the points of needles, a layer of black pigmentary particles was found to line the internal surfaoe of the dense structure whioh corresponds to the sclerotic.

In addition, there was a confused mixture of grey and white granular substanoe, in whioh there was no distinct evidence of remains of the I usual contents of the globe of the eye, though, as will be seen, those ¹ structures exist in foetal life.

The specimens were sent to me preserved in alcohol, consequently the brain was firm, and easy to be removed entire from the cranium.

On raising the anterior lobes gently from the base of the skull, it was ascertained that no nerves connected the brain with the bone anterior to the fifth pair. The base of the brain also exhibited an entire absence of the optic nerves beyond a vestige in a very minute chiasma, as described by Mr. Solly.

)On examining the internal surface of the base of the skull, the usual foramina for the optio nerves are found to be wanting, a con-| dition which is observed with facility in the dried specimens in the Museum of the Royal College of Surgeons. Among these there is one in which there is a vestige of an optic foramen on the left side of the head, while pn the opposite side the surface is smooth and perfect.

_f In the arrangement of the details which have been given above of the appearances observed in the course of the examination, attention has been directed to three points in particular—namely, to the condition of that part of the optio nerve which is situated externally to the skull, and which exists as a mere thread of connective tissue; secondly, to the eye itself, and the structures within, so far as it was necessary to consider them in their efficiency for optical purposes; thirdly, to the internal surfaoe of the skull in its relation to the part of the brain from which the optio nerves take their origin.

The following description of the various structures in the foetal mole will be more general than the above account of them in the full-grown mole, as five specimens instead of one were examined.

On the removal of the skin and~a layer of muscular tissue subjacent, a part of the globe of the eye is exposed. When the whole side of the face and the temporal region are dissected, the eye is found to be in close proximity to the large branch of the facial nerve.

The eye has the usual appearance presented by the organ in most fcctal mammalia. In form globular, and in size proportionate to the head of the animal; the cornea translucent; the sclerotio perfectly distinct, and of dense white tissue; the iris apparent through the cornea, with a clear pupillary aperture.

Between the eye and the facial nerve a small portion of the optio nerve is seen in the superficial dissection, and appears to form an upright pedunole for the globe.

It is necessary to divide the seventh pair in order to examine the deeper parts of the orbit. When the disseotion is completed, and the optio nerve exposed in its whole extent, from the eye to the base of the eranium, the branches of the fifth pair of nerves are brought into view. The main branoh of the seoond division of the fifth nerve lies a little below the optio nerve, parallel with it, and supplies large and numerous branches to the anterior part of the face. There is no necessity to describe minutely the appearanoe presented in the deep disseotion of the orbit, as I observed nothing unusual to require particular notioe. There are some minute muscles attached to the globe whioh do not admit of separation into distinct parts, but completely surround the posterior half of the globe.

To traoe the optio nerve through its foramen to the brain was successfully aooomplished in only one disseotion. After exposing the optio nerve and the eye completely, all the surrounding parts were removed, and a section made through the skull so as to exhibit a lateral view of the interior of the cranium.

The brain itself was disorganized in all the young specimens ; bui in the disseotion just alluded to the optio nerve was seen to pass through the base of the skull, and to enter the membranes to a short distanoe, so that it would have been possible, if the brain had remained perfect, to trace it to its origin.

With regard to the eye itself, no diffioulty was experienced in separating the iris., choroid, and lens. The other structures usually existing in the eye had been so long subjected to the influence of the alcohol that I could not determine their oondition.

It must necessarily happen that many interesting observations are made in the course of an investigation like that which has been briefly described, and many minute details might have been added to this acoount; but it appeared to me to be desirable to limit the details, as. far as possible, to those which were sufficient to establish the remark- \ able physiological fact that the mole, at the time of birth, is endowed l with organs of vision of considerable perfection, while in mature age | it is deprived of the means of sight in consequence of certain changes j which take place in the base of the skull, terminating in the destruc- 1 tion of the most important structures on whioh the enjoyment of the \ sense of sight depends.

"On an Aplanatie Searoher, and its Effects in improving High-Power Definition in the Microscope," by G. W. Royston-Pigott, M.A., M.D.Cantab., M.R.C.P., F.R.A.S., F.C.P.S., formerly Fellow of St. Peter'B College, Cambridge ; communicated by Professor Stokes, Sec. R. S.—The Aplanatio Searcher described by Br. Pigott is intended to improve the penetration, amplify magnifying power, intensify definition, and raise the objective somewhat further from its dangerous proximity to the delioate covering-glass indispensable to the observation of objects under very high powers.

The inquiry into the practicability of improving the performance of microscopio object-glasses of the very finest known quality was suggested by an aooidental resolution in 1862 of the Podura markings into black beads. This led to a search for the cause of defective definition, if any existed. A variety of- first-class objectives, from the -fa to the

failed to show the beading, although most carefully constructed by Messrs. Powell & Lealand.

Experiments having been instituted on the nature of the errors, it was found that the instrument required a better distribution of power; instead of depending upon the deepest eyepieces and most powerful objectives hitherto constructed, that better effects could be produced by regulating a more gradual bending or contraction of the excentrical rays emanating from a brilliant mioroscopio origin of light.

It then appeared that delusive images, which the writer has ventured to name eidola,¹ exist in close proximity to the best focal point (where the least circle of """fay"" finds its locus). _

(I.) That these images, possessing extraordinary characters, exist principally above or below the best focal point, according as the objective spherical aberration is positive or negative.

(II.) That test-images may be formed of a high order of delicaoy and accurate portraiture in miniature, by employing an objective of twice the focal depth, or, rather, half the focal length of the observing objective.

(HI.) That such test-images (whioh may be obtained oonveniently two thousand times less than a known original) are formed (under precautions) with a remarkable freedom from aberration, whioh appears to be reduced in the miniature to a minimum.

(IV.) The beauty or indistinotness with whioh they are displayed (especially on the immersion system) is a marvellous test of the correction of the observing objective, but an indifferent one of the image-forming objective used to produce the testing miniature.

These results enable the observer to compare the known with the unknown. By observing a variety of brilliant images of known objects, as gauze, lace, an ivory thermometer, and sparkles of mercury, all

i From €»lm\ov, % false spectral image.

[page] 412

formed in the focus of the objective to be tested with the microscope properly adjusted, so that the axes of the two objectives may be coincident, and their corrections suitably manipulated, it is practicable to compere known delusions with suspected phenomena.

It was then observed (by means of such appliances) that the aberration developed by high-power eyepieces and a lengthened tube, followed a peculiar law.

A. A lengthened tube increased aberration faster than it gained power (roughly the aberration varied as v³, while the power varied as v).

B. As the image was formed by the objective at points nearer to it than the standard distance of 9 in., for which the best English glasses are corrected, the writer found the aberration diminished faster than the power was lost, by shortening the body of the instrument.

C. The aberration became negatively affected, and required a positive compensation.

D. Frequent consideration of the equations for aplanatism suggested

the idea of searching the axis of the instrument for aplanatio foci, and that many Buoh foci would probably be found to exist in proportion to the number of terms in the equations (involving curvatures and positions).

E. The law was tben ascertained that power could be raised, and definition intensified, by positively oorrecting the searohing lenses in proportion as they approached the objective, at the same time applying a similar correction to the observing objective.

The ohief results hitherto obtained may be thus summarized.

The writer measured the distance gained by the aplanatio searcher, whilst observing with a $-in. objective with a power of seven hundred diameters, and found it two-tenths of an inch increase; so that optioal penetration was attainable with this high power through plate-glass nearly $ in. thick, whilst visual focal depth was proportionably increased.

The aplanatio searcher increases the power of the microscope from two and a half to five times the usual power obtained with a third or C eyepiece of 1 in. focal length. The £ thus acquires the power of a the penetration of a And at the same time the lowest possible eyepiece (3-in. focus) is substituted for the deep eyepiece formed of minute lenses, and guarded with a minutely perforated cap. The writer lately exhibited to Messrs. Powell & Lealand a brilliant definition, under a power of 4,000 diameters, with their new " £ immersion " lens, by means of the searcher and low eyepiece.

The traverse of the aplanatic searcher introduces remarkable chromatic corrections displayed in the unexpected colouring developed in microscopic test objects.¹

The singular properties, or rather phenomena, shown by eidola, enable the practised observer in many cases to distinguish between true and delusive appearances, especially when aided by the aber-rameter applied to the objective to display excentrical aberration by cutting off excentrical says. y

Eidola are symmetrically placed on each side of the best focal point, as ascertaiued by the aberrameter when the compensations have attained a delicate balance of opposite corrections.

If the beading, for instance, of a test-object exists in two contiguous parallel planes, the eidola of one set is commingled with the true imape of the other. Bat the upper or lower set may be separately displayed, either by depressing the false eidola of the lower stratum, or elevating the eidola of the upper. For when the eidola of two contiguous strata are intermingled, correct definition is impossible so long as the aperture of the objective remains considerable.

One other result accrues : when an objective, otherwise excellent, cannot be further corrected, the component glasses being already closely screwed up together, a further correction can be applied by means of the adjustments of the aplanatic searcher itself, all of whioh are essentially conjugate with the actions of the objective and the variable positions of Jts component lenses; so that if Sx be the traversing movements of the objeotive lenses, Sv that of the searcher, F the focal distanoeof the image from the objeotive when Sx vanishes, / the focal distance of the virtual image formed by the facet lenses of the objeotive.

The appendix refers to plates illustrating the mechanical arrangements for the discrimination of eidola and true images, and for traversing the lenses of the aplanatio searcher.

The plates whioh the author supplied with the paper also showed the course of the optical pencils, spurious disks of residuary aberration and imperfect definition, as well as some examples*>f "high-power resolution " of the Podura and Lepisma beading, as well as the amount of amplification obtained by camera-luoida outline drawings of a given scale.

"On Supra-annual Cycles of Temperature in the Earth's Surface-crust " was a paper, by Professor C. Piazzi Smith, F.B.S., which, owing to press of matter, must stand over till our next number.

ETHNOLOGICAL SOCIETY.

Apbil 26th.—Professor Huxley, F.B.S., president, in the chair. Dr. Donovan read a short paper on the importance to the ethnologist of a careful study of the characters of the brain.

Mr. E. B. Tylor then read a paper " On the Philosophy of Beligion among the Lower Races of Mankind." — Taking the doctrine of spiritual beings as the minimum definition of religion, the author described it as Animism. The conception of a soul, combining the ideas of ghost and vital prinoiple, forms the starting-point of religious philosophy among the lower races. Animals and inanimate beings are ajpo supposed to possess souls, and all nature is acted on by soul-like spiritual beings, many of which may be human souls or manes. Trees, rivers, &o., are also Supposed to possess spirits, and the Bavago polytheist thenoe extends his conceptions to that of greater deitieB, as the sun and moon. Dualism springs up in religion by separating the causes of good from those of evil. The culminating conception of a Supreme Deity is well known to many of the lower raoes.

Mr. Pusey, Mr. Howorth, and Dr. Hyde Clarke spoke upon this communication.

CHEMICAL SOCIETY.¹

April 21st.—Professor Williamson, F.B.S., wesident, in the ohair. Mr. T. Patohett was elected a fellow.

Professor Bosooe, F.B.S., delivered a lecture " On Vanadium."— This metal was discovered in 1830, by Sefstrdm, in the celebrated Swedish bar-iron made from the Taberg ore. Sefstrdm ascertained some of the most peculiar characters of this substance, proved it to be a new element, and prepared some of its compounds in the pure state. The reaotions by whioh vanadium can be separated and distinguished from all the other elements are :—lgt. The formation of a soluble sodium vanadate when the vanadium oompounds are fused with sodium carbonate. 2nd. The formation of an insoluble ammonium vanadate when sal ammoniac is added to the solution of a soluble vanadate. 3rd. The production of a splendid blue solution when this ammonium Bait, dissolved in hydroohlorio aoid, is warmed with reducing agents, such as oxalio aoid.

Sefstr&m, not having leisure to prosecute the full examination of the properties of the new metal, handed over his preparations to Bcrzelias , onu it U U, the investigations of the great Swede that We owe almost all our acquaintance with the chemistry of vanadium.

Sinoe Berzelius's time, vanadium has been discovered in many minerals, of which a lead ore containing lead vanadate, and called by the mineralogists, vanadinite, is the most important.

In 1865 Professor Roscoe came into possession of a plentiful source of vanadium, in a by-produot obtained in the preparation of cobalt from the copper-bearing beds of the lower Keuper Sandstone of the Trias, at Alderley Edge, in Cheshire. Following, in the main, the process of preparation adopted by Sefstrom, Professor Boscoe obtained, from the above-mentioned Bouroe, several pounds of pure ammonium vanadate, from whioh all the other oompounds of vanadium can be prepared.

What, now, were the conclusions to which Berzelius arrived, from his experiments concerning the constitution of the vanadium compounds ? He assigned to its three oxides the formula) YO, V0₂, and V0₈, whilst the chloride was represented by VC1₈. The atomio weight of the metal he found to be V=68'5.

Some years afterwards, Bammelsberg observed that vanadinite, a double salt of lead-vanadate and lead chloride, is isomorphous with apatite and with mimitesite, the former oontaining phosphoric, the latter areenio acid. This crystallographio analogy would lead us to conclude that the oxide of vanadium in the vanadinite has the formula V_s0₅, agreeing with the corresponding oxides of phosphorus and arsenic, P_flO_s and As_fl0₅; but the unyielding ohemioal faotH ot Bqil-zelius compel us to view the oxide in question as YO_s. It was, then, evident that here waB either an exception to the law of isomorphism, Or else Berzelius's views were erroneous.

Professor Bosooe, in order to endeavour to clear up this question, had carefully repeated Berzelius's experiments, and he found them confirmed in every particular ; but, having pursued the subject further than Berzelius, he had succeeded in obtaining the key to the enigma presented by the above anomalous crystallographio relations.

The lecturer has proved thafflhe substance supposed by Berzelius to be vanadium is not the metal, but an oxide, and that the true atomio weight of the metal is 513. The vanadic acid, YO_s, of Berzelius, hence, becomes V_a0₅, corresponding to P_flO_a, and As_aO_a ; and the above-mentioned isomorphism is fully explained. The sub-oxide of Berzelius is a tri-oxide, V₂0, ; whilst the terohloride (VC1₈) of Berzelius is an oxychloride, V0C1₈, corresponding to oxychloride of phosphorus, P0C1₈.

Professor Boscoe has succeeded in obtaining bromine and iodine compounds of vanadium, and also various metallic vanadates. He went on with his lecture by pointing out that the characters of the

» Alluded to by Mr. B«ad«, F.R.8., in Popular 8eitnet Review for April, H