Gossip.

BY RICHARD A. PROCTOR.

I SEE that some Fellows of the Royal Astronomical Society have been complaining-for the fiftieth timethat the Monthly Notices only come out a month after the meeting when they were read. In reply to the remark that when I conducted the notices the papers came out a fortnight earlier, those responsible for the gross dilatoriness complained of, answered that it was better to bring the papers out free from errors than in good time. To the implied idea that there were more errors in the papers in my time than now, I reply that the insinuation is untrue. The proportion of errata to the quantity of matter was if anything less in my time; but the quantity of matter was much greater. To the question, how I managed to get out the Notices in good time, I answer that if I had not managed to do so I would not have accepted the fifteen pounds paid quarterly for the work. As a matter of fact, I did work worth to me about six times the stipend for which I consented, as a favour to the Council, to hold the office while Professor Cayley was President.

BEING very far from England at present (but in a few weeks now I shall be in the old country again) I see with some dismay such statements as "Hallyards" makes respecting me, in KNOWLEDGE for May 29 (let. 1723, p. 465); for by the time my correction arrives the idea will have been wholly absorbed by many readers that the views he has attributed to me are really mine, and correction is apt to avail little after that. "The Conductor of KNOWLEDGE has remarked somewhere," he says, "that it is rash to suppose all bodies to be moving in curves, that probably many stars move in straight lines." Where and when have I ever said anything so absurd? I know of no time since I was ten or twelve years old, when I have not known better,-always excepting my sleeping hours, during which I may, for aught I know or can remember, have dreamed of stars moving in straight lines, just as I have dreamed of dead folk talking to me, and the like. A little further on "Hallyards" says that he thinks "the Conductor of KNOWLEDGE has remarked somewhere that space cannot be infinite." I have said that we cannot imagine space otherwise than infinite, most assuredly not what "Hallyards" attributes to me. The nearest approach to it has been my remark that we cannot conceive infinite space, a mightily different matter. (I cannot conceive how "Hallyards" has misapprehended me so strangely; but the fact that he has done so is patent.)

HAVING imagined me to have invented stars moving in straight lines" Hallyards" gets up a sort of discussion, between this semi-idiotic second self he has made for me, and his own self. "I do not see,' he says, "how this can be if there is even the very least pull on one of them from the nearest larger body: if gravitation be indeed true for all distances, then I do not see how any body can avoid an orbit." Neither do I, but my second self is made to argue very foolishly that a body can avoid an orbit. "It will be replied," "Hallyards" remarks, that their rate of translation will overcome the pull of the nearest body,"-though any one who would reply thus would say anything. "But there again," he proceeds, seems ("seems, nay is, I know no seems")

"another exception to the universality-or at least, the autocracy of gravitation." All this is naught.

IT is a misfortune that few men of science will condescend to avoid the use of technical terms, while scarcely any seem able, even if they were willing, to write intelligibly even when they use ordinary words. But it is a worse fault still that many writers about scientific matters seem to consider the constant use of metaphors essential to effect. It would almost seem that they imagine the facts of science to be without interest unless presented in fanciful form.

HERE for instance is a passage from an article in the Times for May 27, in which the application of photography to science is considered. (The article, by the way, presents, as very striking and novel in the middle of 1885, rather less than I described as accomplished facts in the second number of Longman's Magazine, two years and a half ago.):

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Every fresh step in optical mechanics has multiplied the working capital of philosophy" (imagine the mul tiplication of capital by walking!). "A refractor like that at Washington widens at a bound the reach of astronomical generalisations." (Imagine, yet again, something which widens the reach of some other things by bounding!). "It resembles for the eyes an extension of a range of several miles for a gun.' (An extension in what by a yard or by half a mile.) "The weakness of the degree? for a range of several miles may be extended telescope is that, as the eyes are quickened and sharpened by it, so it is chained by and to the eyes.' (The eyes are quickened and sharpened, it would seem, by something-whether the telescope or the telescope's weakness, is not clear-which is chained by them and to them! Surely as a metaphor this surpasses the rat which Castlereagh "smelt," and saw "floating in the air," but promised presently to "nip in the bud.") "Chemistry puts forth its prepared gelatine and bids it concentrate itself on hoarding each thin ray which and ministers of grace defend us! strikes it, as children's pence in a school bank." (Angels What may this

mean? Do the thin rays strike chemistry like children's pence in a school bank? or do they strike gelatine after that strange fashion? Then, what is a thin ray? And why should a thin ray be more aggressive than a fat one? or be hoarded more carefully ?)

THE Darwin Medal for 1884-5-founded by the Midland Union of Natural History Societies-has been awarded to our contributor, Mr. W. Jerome Harrison, F.G.S., for his geological researches. MESSRS. KEGAN PAUL, TRENCH, & Co. will publish immediately a new and much cheaper edition of Mr. Francis George Heath's "Autumnal Leaves."

LONDON BY NIGHT.-Into the grim world of "London by Night," Mr. Thomas Archer has recently made a fresh tour of discovery, and has recorded his impressions in an article which is to appear in Cassell's Magazine for July, with illustrations from a well-known pencil.

THE EARTH'S ANNUAL METEORIC GROWTH.-It is calculated by Dr. Kleiber, of St. Petersburg, that 4,950 lb. of meteoric dust fall on the earth every hour-that is, 59 tons a day, and more than 11,435 tons a year. I believe this to be considerably short of the truth. It sounds like a large annual growth, and the downfall of such an enormous mass of meteoric matter seems suggestive of some degree of danger. But in reality Dr. Kleiber's estimate gives only about twenty-five millions of pounds annually, which is less than two ounces annually to each square mile of the earth's surface. -R. A. Proctor, in Newcastle Weekly Chronicle.

THE

THE FACE OF THE SKY.

FROM JULY 3 TO JULY 17.

BY "F.R.AS."

HE recent indications of renewed solar activity in the shape of grand spots render the sun a very interesting object whenever the sky is clear. The face of the night sky will be found depicted in Map VII. of "The Stars in their Seasons." Twilight persists all night long during the fortnight which these notes cover. Mercury is an evening star, and, towards the end of the next fourteen days, may quite possibly be picked up with the naked eye over the W.N.W. horizon after sunset. Venus is an evening star, too, and may certainly be seen in the same part of the sky. She is still a very insignificant and uninteresting object in the telescope. Jupiter may be caught pretty close to the horizon after dusk; but at this time he is too low down for telescopic examination. The only phenomena of his Satellites theoretically visible are the reappearance of Satellite IV. from eclipse at 8h. 28m. 40s. on the 3rd; the egress of the shadow of Satellite III. at 8h. 27m., and the occultation of Satellite II. at 8h. 50m. on the 13th; the occultation of Satellite I. at 9h. 38m. on the 14th; and the egress of the same satellite at 9h. 15m. the next night. The observation of any of these is, however, doubtful. Mars and Saturn are invisible, as is Neptune too; but Uranus may possibly be seen under unfavourable conditions as soon as it is sufficiently dark. The Moon enters her last quarter 25'6 minutes after noon on July 5, and will be New at 5h. 15.8m a.m. on the 12th. High tides may be expected about this date. No occultations of fixed stars will take place during the time which our notes cover, save one of Aldebaran in bright sunlight at 11h. 23m. 26s. a.m. on July 9. When they begin, the Moon is in Pisces, across which she is travelling until 4 p.m. on the 6th, when she enters the N.W. corner of Cetus, quitting it, however, for Aries at 2 o'clock the next morning (that of the 7th). At 6h. 30m. a.m. on the 8th, she crosses the boundary between Áries and Taurus. Her journey through Taurus occupies her until 4h. 30m. p.m. on the 10th, at which hour she passes into the narrow northern strip of Orion. By three o'clock the next day, she has crossed this and emerged in Gemini. At 2h. 30m. p.m. on the 12th, she leaves Gemini for Cancer, and Cancer for Leo in turn at 1 a.m. on the 14th. She is travelling through Leo until 8 a.m. on the 15th, when she descends into Sextans, to re-emerge in Leo at one o'clock the same afternoon. She finally leaves Leo for Virgo at 1 p.m. on the 16th, and is, of course, still in the last-named constellation when these notes terminate.

THE members of the Society of Telegraph Engineers, at the invitation of their president, Mr. Spagnoletti, Telegraph Superintendent of the Great Western Railway, paid a visit to the Swindon Works on Tuesday. Some five hundred members went down by special train, and the visitors spent a most interesting and instructive day. The works, as may be imagined, are of colossal proportions; they cover an area of thirty acres, and give employ. ment to upwards of 5,000 men. No effort was spared, on the part of the railway officials, to make the trip pleasant and profitable to all who took part in it. The possible output is at the rate of one engine, six carriages, and fifty trucks per week.

WE give the following from a paper entitled "On a variation in the size of an image on the retina according to the distance of the background on which it is seen," by Alfred Brothers, F.R.A.S., which was read before the Manchester Literary and Philosophical Society. "The effect on the retina when the eyes have been fixed intently for a few seconds on a brightly-illuminated coloured object is well known; the colour complementary to the one looked at always appears when the gaze is removed to a colourless surface. It is also a matter of common observation that when the eyes have been directed to a bright light for a short time, the image left on the retina as seen when the eyes are averted is dark; but if the eyes are rapidly opened and closed the image is still seen bright. I am not aware, however, that it has ever been noticed that this image varies in size according to the distance of the background to which the eyes are directed. A circle of gas-jets, perhaps, affords the simplest test. It will be seen after looking at the circle of light for a few seconds-in some cases a more or less lengthened gaze at the light is necessary, owing to the varying sensitiveness of the retina-that, if the vision be turned to a distant background, the size of the image is instantly enlarged, and then, if the eyes be directed to a near background, the image is reduced in size. If any difficulty should be found in seeing the reversed image of the gas-jets, it may readily be seen as a bright object by rapidly closing and opening the eyelids. The effect is the same as if the image were seen through a cone-the apex of the cone being held close to the eyes. In other words, the effect is the reverse of the ordinary rules of perspective."

Only a small proportion of Letters received can possibly be inserted. Correspondents must not be offended, therefore, should their letters not appear.

All Editorial communications should be addressed to the EDITOR OF KNOWLEDGE; all Business communications to the PUBLISHERS, at the Office, 74, Great Queen-street, W.C. IF THIS IS NOT ATTENDED TO, DELAYS ARISE FOR WHICH THE EDITOR IS NOT RESPONSIBLE.

The Editor is not responsible for the opinions of correspondents. All Remittances, Cheques, and Post-Office Orders should be made payable to MESSRS. WYMAN & SONS.

NO COMMUNICATIONS ARE ANSWERED BY POST, EVEN THOUGH STAMPED AND DIRECTED ENVELOPE BE ENCLOSED.

CONVENTIONAL EVOLUTION.

[1790]-Kindly allow me to make one or two suggestions upon what has been happily termed "Conventional Evolution." Every great teacher has followers who lay undue stress upon certain of his doctrines; and sometimes it happens that such doctrines are the least proven, as universal truths, by the master. This, I think, has been the case with Darwin. He certainly relied very much upon small variations in expounding his theory of "natural selection"; but it is doubtful whether he would have made them a sine quâ non, as his disciples do. Cataclysm and special creation were the favourite hypotheses of our forefathers. We have now gone to the other extreme, and nothing but a growth by infinitesimal gradations will suit us. No kind of break is tolerated. It is assumed that Nature is opposed to any sort of leaps, and, in accordance with that idea, many of our present teachers point to an imaginary chart of brutal ancestry descending by a slow unbroken chain to the parent man-ape. The "missing links," of course, may yet be found, but till they are why draw so largely upon imagination? Has Nature no phenomena by which the breaks can be explained? Does she never pass abruptly from law to law? The author of the "Vestiges" made such a suggestion, but no one, it seems, has ever followed it up. In chemistry we pass from one substance to another by sudden steps. You cannot link calomel to corrosive sublimate by gradations of chlorine. The diamond, too, enters suddenly under the control of laws which have no apparent concern with common charcoal. But leaving the inorganic world on one side, what are we to say to the leap Nature makes in creating a Shakespeare or a Beethoven? Can we lead up to them by a slow ascending series of their ancestors, or do they suddenly appear, like Minervas, fully formed?

I had something to say about Darwin's law of correlation being so much neglected of late, but I am afraid I have already taken up too much space. GAMMA.

SPIDER.

[1791]-If one may hazard a conjecture on so short a description, the spider referred to by "Hallyards " is perhaps Thomisus abbreviatus. This is a buff-coloured spider with the body abruptly bent down behind, and with an angular projection on each side of

the upper part at the edge of the bend. But it has five small pits on the upper surface. Some members of this genus are found in flowers, and I have seen one so closely resembling in colour the flower (a composite one) amongst whose florets it was lying in

wait for prey, that it was with great difficulty detected. I enclose a sketch of Thomisus abbreviatus, which may perhaps enable "Hallyards" to decide whether the determination is correct.

E. A. BUTLER.

THE PREVENTION OF COLLIERY EXPLOSIONS. [1792]-How many more colliery explosions are we to hear of without preventive measures being at least attempted? Can any expert inform me what would be the cost of the installation of the electric light in mines? Herr Julius Maier, in a recent article in the Fortnightly on "Electricity," has proved that the mine-lighting question by electricity has been brought within the range of practical possibilities; and I myself, two years ago, heard Professor Tyndall confess it could be managed, and these terrible disasters averted, if it were not for the expense. Surely some association or society might be formed to collect funds for such a purpose. The British public is ever ready to come forward upon charitable pretexts, and if once it was fully understood that the illumination of mines by electricity was not an impossibility, subscriptions would be forthcoming. Science, who never turns her back upon us when we need her aid, can help our poor miners now if man will let her. M. E. MAVROGORDATO.

ROCKS OF CHARNWOOD.

[1793]-I am pleased to know that my article on Charnwood has led Mr. Fletcher and his friends to study the remarkable rocks of that region. The quarry which he describes in Brazil Wood is clearly the one to which I referred, and I am glad that he saw clear evidence there of the intrusion of the granitic into the slaty rocks. If he visits the spot again, I hope he will search for the garnets which have been plentifully developed in the altered slate. I found them most abundantly in the corner farthest from the gate. They are dark-nearly black-in colour, and vary in size from microscopic dimensions to about the eighth of an inch in diameter. The pebbles and gravel lying on the top of Mountsorrel hillsome 200 feet above the level of the Soar Valley-probably mark the stage of depression which followed the deposit in England of the great chalky boulder clay-itself the moraine of a mighty glacier. England went down, perhaps, 2,000 feet in the west and south, but much less in Leicestershire; perhaps not more than 400 feet. Still, this change would be quite sufficient to submerge most of the Charnwood hills, including Mountsorrel, and during the washing and redistribution of the surface boulder clay which then took place, the pebbles now forming a thin covering to the hill-top may have received their rounding.

But Mr. Fletcher states that he found bones and fragments of pottery in the lower part of the stratum containing the pebbles. This I consider to be owing to the fact that the stones have been moved partly down the hill by rain, &c., since the time of their original deposition. The real summit of Mountsorrel-long since quarried away-was much higher than the part which now remains. All such exposed summits get washed bare, and the débris is pushed down the slopes. I may add that a fine flint javelin-head which I found in probably a corresponding position to the bones, &c., in 1876, would possibly be coeval with them, and that bones, pottery, and all are, I should consider, referable to a period somewhere about the time of the Roman occupation of this country. A comparison with the numerous specimens of pottery in the Leicester Museum would help in settling this point.

I may add that I think it would be a good thing if local workers in science would favour us more frequently with short, condensed notes on matters which come under their observation. It is certain that many useful and interesting facts are lost to the world of science, for, though observed, they are not recorded.

W. JEROME HARRISON.

TWO-SPEED GEARING.

[1794]-In reply to "W. J.," Bown's two-speed gearing performs excellently, provided it is so adapted to a tricycle that it can be changed from power to speed easily. JOHN BROWNING.

A PARADOX.

[1795]-Your correspondent "Coleford" (1772) propounds no "paradox." His theory of the rate of increase of grandfathers, great-grandfathers, &c., only holds good if there is never such a thing as an inter-marriage between two people descended from the same ancestors, however remotely they may be connected. Each grandfather represents a family one degree removed, each additional great-grandfather another family two degrees removed, and

so on.

Again, it is in no way necessary, as "Coleford" seems to think,

that all the great-great-grandfathers or great-great-great-grandfathers should "exist on the earth at one time."

But, in the first place, families cannot help intermarrying as I have indicated, and, in the second place, it is not unusual for a husband to be old enough to be his wife's grandfather. R. L.

[1796]-The solution of the rather curious paradox which occurs upon page 533 is to be found in the following simple facts:Although every single individual in ordinary parlance is said to possess two grandfathers, four great-grandfathers, &c., these various antecedents are at once, grandfathers, &c., to many other individuals.

Moreover, when marriage is contracted between members of the same family, as is often the case among certain African tribes, it occasionally happens that a person has but one grandfather, his father's father and his mother's father being one and the same.

8

A glance at the annexed diagram will show at once how the matter stands; the dots represent individuals, and those at the extremities of each angle indicate the parents of the person forming the apex thereof pointing downwards. From this it will be seen that if we allot to any individual in the lower line (A for example) his common share of ancestors, he will posses a grandfather on his mother's side and another on his father's side (apparently two, but in reality only one); the fathers of these, and of their wives, make four great-grandfathers (still represented by one) who, with their wives, are the offspring of eight great-great-grandfathers (the complete eight, as a matter of fact, being a single individual of the first pair). Again, ten boys, each having a father, should make ten fathers in all, but if the boys are brothers there is only one father. All humanity must be more or less related, and the evident reason which your correspondent requires why the population increases instead of decreasing, is because in almost every case a grandfather has more grandchildren than a single grandchild has grandfathers. ALEX. MACKIE. [Solutions are also sent by "Scotus," George Falkner, F. W. H., &c.-ED.]

SYMMETRY.

[1797]-I admit, in common with "An Old Draughtsman" (1742), that questions of taste frequently appear to be very complex. But is he right in using the word "symmetry as synony. mous with balance? Surely he is not. Nevertheless, he does not stand alone in this misuse of the word; it occurs over and over again in journals devoted to art subjects. Equiformity, or equipoise, is not symmetry. Symmetry, according to our dictionaries, means harmony of proportion-the proportion of the several parts to the whole together. A work either of Nature or of art may be equipoised without being symmetrical. As to the complexity of matters of taste, it may be said that it frequently disappears as soon as the end to be attained can be clearly formulated. ANOTHER OLD DRAUGHTSMAN.

LETTERS RECEIVED AND SHORT ANSWERS.

W. C. PENNY was horribly shocked (as well he might be) to read on p. 535 a description of a breakwater which "consists of a number of small boys (!) to be so fastened together that each may float on the water." Thank U.-JOHN SILCOCK knows of a lot of small boys who would suit admirably, and would arrange with the inventor to supply them.-THOS. RADMORE. Thanks for light thrown on the matter. I am a little afraid that that Blue Book is lost in the abyss of the office.-JOSEPH HOMER. Articles sent here "in July, 1883," and unaccompanied by stamped and directed envelopes, must, ages ago, have departed to that bourne whence no MS. returns.-MISS JENNIE MCNEIL. The libration in longitude of the moon varies at each successive lunation, and has to be calculated separately, by a somewhat operose formula. The full moon of June 27 will have passed ere these lines are in print; but in the case of the succeeding one (that of July 26) the

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libration in longitude will bring more of the western part of the surface into view.-AUGUSTUS J. HARVEY urges the necessity for national electrical engineering and phonetic training colleges. He is also anxious for the establishment of hospitals for self-mesmerism or self-healing, though why a man cannot cure himself at home he fails to explain.-DR. KNIGHT sends comments on a decision (against him) of a local County Court Judge. This is not, however, the place to review legal judgments in.-W. ROBINSON points out, in connection with the article on p. 515, that the omission of any reference to a movable pulley makes it read as though, the rope being simply passed over one fixed pulley, overhead power was in some way gained, the fact being that, under such circumstances, it would need a little over 100 lb. pull upon one end of the rope to pull up 100 lb. at the other.-JOHN PARRY. About as much connection with the scientific doctrine of chances as it has with the Rig-Veda. You will find the concoctor of it described in the 5th Geo. IV., c. 83, s. 4.-AN INSULTED LOVER OF KNOWLEDGE WHO DETESTS HUMBUG. I have received your courteous, logical, and gentlemanlike letter. See section 3 of final paragraph on p. 505 of last volume. Let me implore you to keep your temper.-JAMES EDMONDS. The bright disc of the sun which we see, and which astronomers call the "Photosphere" is a species of self-luminous cloud surrounding the sun; just like our clouds, only made up of metallic vapours instead of water. It is needless to say that the temperature must be stupendous to maintain metals in a gaseous form. Well, such spots as you saw are depressions in this photosphere. If you have ever watched the water in a mill-pond, near the penstock or sluice, you will have noticed how the surface exhibits little funnel-shaped depressions. Now, in some way ill-understood, it is supposed that sun-spots have their origin in a somewhat similar sucking down of the matter of the photosphere, and the cooler gases, of course, brought down from above would look darker than the surrounding highly-heated ones. The nucleus of the spot, which seemed to you black by contrast, would be unbearably brilliant if it could be isolated. You should read "The Sun," by the Conductor of this journal, or the volume with the same title by Professor Young, in the "International Scientific Series."-J. V. HALL suggests to Hallyards" that he should comment on commence" for "begin," penetrate for pierce," and, in fact, on the employment of words of Latin origin generally, when Saxon ones exist and are more expressive. We have largely to thank Dr. Johnson for this depravation of the English language. "Hallyards" resides permanently on the Continent.H. R. B. I recognise the justice of much which you advance; but you must bear in mind that the dicta in question were put forth as those of a dead woman of the highest literary ability, and of almost world-wide fame (or notoriety), and neither as arguments, nor with any expression of approval. I suppose that if I reproduced a conversation here in which Spinoza was an interlocutor, you would accuse me of admitting evidence for Pantheism! You, however, yourself, did unquestionably trench on theological ground, inasmuch as yours was a categorical contention for positive miraculous interference in explanation of a phenomenon of nature. It did not strike me that "Ultra-gas" was advanced to explain the action of gravity. The whole question you raise is a delicate and difficult one. first reply to Dr. Lewins, for example, at the beginning of p. 534, in illustration of what I have to contend with.-GENERAL BABBAGE. Can any possible advantage accrue from protracting the discussion ? As for "calumnies," had the late Mr. Sheepshanks and the present Sir George Airy (to name only two people) nothing to complain of in that respect? In cases of "Athanasius contra mundum," I always think myself that the odds against the saint being right are overwhelming.-C. TURNER. Should have been sent to the publishers.-W. As it will apparently gratify you to have the last word, by all means do so. I can only deplore, for the sake of KNOWLEDGE that you do not edit it. Its circulation could hardly fail to rise another 25,000 a week, or so, per saltum.D. TATTERSALL. To varnish a map you must first size it. The size is made by boiling clean parchment cuttings in an earthenware pot and straining it. Two coats of this should be first brushed over your map. Then, when all is thoroughly dry, varnish it with Crystal varnish," which you can buy at the shops. Mind and use a large flat brush, and do not drive the varnish too bare. Do it in a warm place. The magnifying power of your telescope is 30 diameters.-J. H. WARD should consult the previous articles on the same subject which have appeared here. I question if such a table of the average dimensions of the various parts of the body as you ask for exists, or could be compiled. Your idea that people in whose outstretched arms a line passing through the middle of the inner fore-arm passes when produced inside the shoulder-joint are more remarkable for mental than physical perfection, can only be established or disproved by observation.-I. J. COLLINS. You are, I imagine, under a delusion as to the general benefit of the opera

See

tion to which you refer. It may be beneficial to some of the filthiest and most degraded races in hot climates, but (as any Indian doctor will tell you) no white man with the average cleanliness of our race, ever has the very slightest need for it in the tropics; while you have only to consult the first qualified medical man you meet to learn how baseless your notion is of its advantage in this country. Forgive me for saying that your whole reasoning is fallacious. It is Art and not Nature that perpetuates hereditary disease by keeping people alive who would infallibly succumb but for its aid. How long do you think the breed of racehorses would remain pure-or fancy pigeons continue without reversion to their ancestral form of the blue rock, but for the most diligent and watchful care on the part of breeders ? All this cuts at the very root of your argument.-JAMES ELLIS, in ascending a dry sewer-shaft in Leeds about a year ago, discovered a half-grown frog, with its mouth (seemingly) entirely sealed up. This he gave to a local medical practitioner, who kept it in a Ward's case; where, for some time, no alteration in its mouth took place. Upon the production of the frog, however, for the inspection of some naturalists, it was found to have adapted itself to its changed circumstances, and, under the influence of light and the presence of insects, to have opened a mouth useless to it in the blackness of darkness of the sewer. Our correspondent's idea is that the frog was developed from some spawn thrown away in the water in which some watercresses had been rinsed. Having kept batrachians for many years, I can myself say that when they hybernate, either inspissated saliva, or something, does form a kind of skin, which makes it very difficult for them to open their mouths on their return to their usual life.-DR. CURRAN. Received with thanks. Will communicate with you by-and-by as to your idea of reproducing them.-W. H. GREENE. Thanks, but crowded out for want of space.-DR. LEWINS. I am entirely with you as to the utter unsoundness and untenability of much which you assail; but when you proceed categorically to assert, in effect, that matter is eternal, and that what the overwhelming majority of mankind agree in calling mind, soul, or spirit is immanent in it, and neither has, nor can have, any separate existence, I can only regard such assertion, in the existing condition of our knowledge, as (in Scottish legal phraseology) "not proven.” All I can say is 'Ayvośw.-COMMENTATOR. The Conductor returns to England in a week or two (see p. 527 of last volume), and it shall be submitted to him. Once more, thanks for artistic picture.-J. C. CLANCHY. Utterly out of place in a scientific journal, however suitable to a trade one.-HALLYARDS. "Est modus in rebus; sunt certi denique fines quos ultra citraque nequit consistere" decorem. If the Times can afford to hint at one of your illustrations, I can'tI can't indeed. The entire subject savours de la saleté; and I was sorry afterwards that I did not merely acknowledge the receipt of that correspondent's letter, instead of replying to it in a form to provoke a rejoinder. Would you like your MS. returned ?-HOWARD G. TOZER.-The Conductor will receive your letter on his return to England later on in the month.-F. W. KIND. (1) There is no better work than Schmidt's "Doctrine of Descent and Darwinism,' published in the "International Scientific Series," by Kegan Paul, Trench & Co. (2) There is no such a thing as a cheap scientific dictionary, (3) nor does such a pamphlet on engineering as you ask for exist. (4) The volumes of the "Chandos Classics," published by F. Warne & Co., contain editions of the poets suitable to your wants. (5) This question is simply an impertinence. What business have you, or any one else, to inquire into the editorial arrangements of this journal ?-F. W. H. DoYLF. (1) The orbits of the planets are by no means accurately in the same plane. That of Mercury is inclined 7° to the ecliptic or plane of the earth's orbit; Venus's 3°; Saturn's, 24°, &c.; while among the planetoids the inclination of Pallas's orbit is nearly 35°. If, though, as is supposed, the whole solar system had a common nebulous origin, its components would naturally be spread out approximately in the plane of the equator of the original rotating vaporous mass. (2) The path of any body describing an orbit-or even passing only once round the sun-depends upon the direction in space from which it approaches him. (3) From the elementary principle that "action and reaction are equal and opposite." The air rushing out drives back the vessel containing it precisely with the force with which it does so issue, and as that vessel is, necessarily, attached to your hypothetical ship, it is not hard to see why the latter remains unaffected. Did you ever try to lift yourself by the waistband of your own trousers ?-E. C. H. If you were standing at either flank of a company of soldiers firing, of course not a bullet would go near you. If you, however, stood straight in front of the file which happened to be shooting, the passage of one or two 455 bullets through your person would indicate with sufficient clearness what was going on. To be consistent, though, you ought to maintain that under the former circumstances there was no firing at all!