sermons; but that by Mr. Skewes shows so conclusively on scientific grounds how utterly baseless is the claim of the "Faith-healers to any supernatural powers, that we depart from our rule to speak well of it. On his arguments from scripture we are, perforce, silent.

The Handbook of Physiognomy. By ROSA BAUGHAN. (London: George Redway. 1885.) That certain conformations of features are typical has been abundantly shown by the combined photographs of Mr. Francis Galton, and by those of the recent American observers. Hence any scientific attempt to classify the diverse forms of the various parts of the human face, and to show in what way any peculiar conformation may be expected to correspond with some intellectual peculiarity or gift could scarcely fail to be of value. When however we find Miss Baughan's tract bristling with crazy astrological trash about people being "born under the dominant influence of Saturn"; deriving their temperament from "the influence of Apollo or Mercury"; or exhibiting the "Signature of Jupiter," and the like,

we see at once that it is about as valuable from a scientific point of view as Mother Shipton's dream-book, there or thereabouts.

School Hygiene, and Diseases Incidental to School Life. By ROBERT FARQUHARSON, M.P., M.D. (London: Smith, Elder, & Co. 1885.)-It can scarcely be doubted that in a very large proportion of schools indeed hygiene, if not practically neglected, is made quite ancillary to the one object of loading the pupils up to the very muzzle with as much intellectual pabulum as can by any device be rammed into them. It is, then, alike to teach pedagogues and parents how care for the bodies of growing boys and girls is as essential as are the artifices adopted for training or forcing their minds, that Dr. Farquharson's book is written; and a real and practical work he has produced. He discourses in succession of school buildings, diet, work, and play; gives a capital chapter on the duties of the school doctor; and concludes with a tolerably full account of school diseases. The question of over-pressure in schools meets with incidental discussion, and there are some extremely sensible remarks on school-play. This is a book to be studied by all engaged in the education of children, as well as by those who perforce commit their children to others to be educated.

Key to Euclid's Elements. By JOHN STURGEON MACKAY, M.A., F.R.S.E. (London: W. & R. Chambers. 1885.)-We are a little puzzled by Mr. Mackay's "Key," inasmuch as it contains answers to questions, solutions of problems, and demonstrations of theorems which have no existence in either of the editions of "Euclid " on our own shelves. It quite obviously has reference to some special version of the "elements" of the immortal Alexandrian; but this should have been stated on the title-page. If it be the key to a reproduction of "Euclid" edited by Mr. Mackay himself, which strikes us as being possible, such edition must be a remarkably complete one, inasmuch as a perusal of some of the very numerous answers worked out at length affords convincing proof of the pertinence of the original riders to "Euclid's" own propositions. Possessors of the particular edition of "Euclid" to which Mr. Mackay's "Key" pertains, will doubtless procure it.

Walford's Antiquarian. Edited by EDWARD WALford, M.A. Aug., 1885. (London: Geo. Redway.)-Full of interest to the archeologist, the historian, the herald, and the bibliographer, Mr. Walford's capital magazine may be commended to all unwilling to sever their connection with the mighty past. The continuation of a very readable article on the Bankside playhouses in

Shakespeare's time will be conned with avidity by the modern playgoer who cares to contrast the comparatively rude representations of the Elizabethan Age with the elaborate scenic reproductions of the present day. A "History of Gilds" becomes important at a time when those of the City of London are threatened. Mr. Round puts Professor Freeman on his defence as a historian, while the taste of the more catholic class of readers will be gratified by the perusal of Mr. Johnson's essay on Thackeray and His Works." We should add that we have only directly referred to four out of the twelve articles which make up the number before us.

66

Familiar Trees. By G. S. BOULGER, F.L.S., F.G.S. With coloured plates by W. H. J. BOOT. Part I. (London: Cassells & Co. 1885.) Mr. Boulger begins his series of "Familiar Trees" with a description of that essentially typical English one, the oak; describing, within the compass of eight pages, the structure, habit of growth, uses, and parasites of the brave old tree, and mentioning certain localities in this country in which it attains great size and perfection. Life-sized coloured drawings of the oak-apple and the acorn, and a chromolithographic reproduction of a spirited water-colour sketch of an oak by Mr. Boot illustrate the text.

The Causes and Prevention of Blindness. By Dr. ERNST FUCHS. Translated by Dr. R. E. DUDGEON, with Notes by Dr. ROTH. (London: Baillière, Tindall, & Cox. 1885.) Of all the afflictions that can fall upon suffering humanity that of blindness is unquestionably one of the most fearful; and it is really terrible to read in the short "Report" prefixed by Dr. Roth to the volume now before us "that two-thirds of the 30,000 blind in England, and of the 320,000 in Europe, owe their misfortune merely to ignorance and neglect." Dr. Fuchs' book has its origin in a prize of £80, offered by the London Society for the Prevention of Blindness for the best essay in English, French, Italian, or German "On the Causes of Blindness, and the best Practical Means of Preventing it," and has been published by the Society, which awarded the well-earned prize to its author. The whole subject is treated in a manner at once lucid and attractive; and the perusal of the work will show how widely spread its interest is. A single illustration may be derived from his section treating of myopia, or short-sight, a malady so tremendously on the increase everywhere since the setting in of the educational craze; with reference to which he tells us that "myopia is the cause of 10 per cent. of all cases of blindness of one eye." Surely when concave spectacles and eye-glasses meet one at every turn, there is much to alarm us in a statement like this, given upon such authority. It may further interest a numerous class to learn that immoderate use of tobacco (and also of spirits, though the effect is less marked) causes amblyopia, or partial blindness. Full of the most practical directions for the avoidance and cure of the numerous forms of visual defects described, this is a book which should be studied by every one who values his own sight or that of his children. He that hath eyes to read, let him read it.

We have also on our table The National Review, a collection of thoughtful and scholarly essays, Bradstreet's, The Sanitary News, The Medical Press and Circular, Ciel et Terre, The Journal of Botany, The Country Brewer's Gazette, Electricité, The Ilkley Free Press, The Tricyclist, Wheeling, the inscrutable scientific journal in Arabic, The Co-operative Index to Periodicals, Our Monthly (Rangoon), and Wm. Wesley & Son's Book Circular.

THE number of hands employed in Woolwich Arsenal is 11,200.

triangle, (and can only be equal to that side when the triangle is right-angled) the limitation is not really necessary.

A. The problem leads of course directly to the determination of the volume of the sphere, from the known area of the sphere's surface.

M. Yes; because the polyhedron enclosed within the outer sphere A BED, Fig. 4, differs in volume from the sphere itself, by a volume less than that of the spherical shell between the spheres ABED and FGHK; and this shell may be made as thin as we please by making the radius of the inner sphere as nearly equal as we please to the radius of the outer.

A. Euclid, then, might have determined the solid content of the sphere.

M. Not quite. For he has nowhere shown, nor with his methods is it possible to show, either that the surface of the sphere is equal to the curved surface of the enclosing cylinder, or that the area of an enclosed polyhedron may be made to differ as little as we please from that of the circumscribing sphere. For the last point it would be necessary to show that the area of a plane triangle as a b c Fig. 4, may be made to differ from the area of the spherical triangle abc, by a quantity which vanishes in the limit compared with either area, by making the sides of the triangle small enough compared with the radius of the sphere. No one really doubts this; no one for instance, imagines that an equilateral triangle with one-inch sides on a globe as large as our earth differs appreciably from an equilateral plane triangle with one-inch sides. But it is impossible to prove this.

A. What do we take next ?

M. I think it now may be interesting to determine the areas and volumes of spindles.

A. I should have thought that would require the higher mathe

matics.

M. No; they can be dealt with geometrically, and by a method applicable to so many problems about curved areas, volumes, &c., that it is well worth studying for its own sake.

(To be continued.)

Miscellanea.

OBITUARY.-Mr. W. J. Thoms, the 1872 of Notes and Queries, died at square, Belgravia, on Saturday last. year.

originator and editor up to his residence, St. George'sHe was in his eighty-second

THE necessary arrangements are being made at Chatham Dockyard for lighting the workshops and factories with the electric light, the results of the trial in those of the workshops already lighted by electricity having been found to be satisfactory.

DISCOVERY OF MICA.-A recent discovery of mica at Tallulah, Ga., is reckoned the richest in the world. It is said that blocks a foot square can be taken out, and that the supply is declared inexhaustible. There is such a demand for the mineral in stove making that it has been growing scarce and dear for several years. THE SEVERN TUNNEL.-Considerable progress has been made with the works of the Severn Tunnel. The brickwork in the tunnel is practically finished; the western face of the tunnel is built, and the eastern face has been commenced, the ballasting is nearly completed, and the greater part of the permanent way has been laid. About 48,000 cubic yards of excavation still remain to be done in the English cutting, and about 5,000 yards on the Welsh side. Arrangements for the permanent pumping and ventilation are being practically carried out.

THE Pacific Mills, situate at Lawrence, Massachusetts, are reported to be the largest textile manufacturing corporation in the world, covering forty-three acres; there are four steam-engines of 3,500 horse-power, forty-two small steam-engines, and fifty boilers and eleven turbines of 5,000 horse-power. The annual consump

tion of cotton is 15,000 bales; of wool, 4,000,000 lb., the product of 750,000 sheep. The annual capacity is, in cottons, printed and dyed, 65,000,000 yards; worsted goods, 35,000,000 yards, or a total of 100,000,000 yards; 3,600 females and 1,900 males are employed. The roll pay for the year ending May, 1884, amounted to 1,790,000 dols.

A RAILWAY JOURNEY THROUGH A BURNING FOREST.-During the recent hot weather a curious, but somewhat alarming, incident occurred on a railway in Finland. On approaching the town of Kaipios the driver of a train saw that the forest on both sides of the line was burning furiously, enveloping it entirely in smoke and flames. Afraid of proceeding, he despatched a messenger to the town, and after waiting for three-quarters of an hour, during

which the fire had extended to both sides of the train, an engine arrived through the burning forest with the message that the line could be safely passed. Doors and windows having been well closed, the train steamed into the burning mass, and succeeded in running the gauntlet safely; but the passengers passed an anxious quarter of an hour, the heat being terrific.

SOME interesting statistics in the coal trade have just been published, showing the character of the Welsh trade. The best customer Cardiff has is Port Said, which took 60,000 tons in July, and the least important amongst the principal Buenos Ayres, which took only 12,000 tons. Newport's principal customer is Genoa, which in July took 15,000 tons; Malta only 5,000 tons. Swansea's best customers were the French, Russian, and Genoese ports. During last month Cardiff sent away to foreign destinations, in round numbers, 588,000 tons of coals; Newport, 169,000 tons; and Swansea, 69,000. In the same period Cardiff sent away 13,000 tons of iron and steel; Newport, 7,000 tons of iron and steel; and Swansea, 1,000 tons. Cardiff, 18,000 tons of patent fuel; Swansea, 29,000 tons.

TIMBER GROWTH ON THE PACIFIC COAST OF THE UNITED STATES. -The timber forests of the north-western portion of Washington Territory, U.S., contain a wealth of forest growth which is not met with elsewhere on the globe; 20,000,000 acres of forest growth are environed around the inland waterways of Paget Sound, with a coast line of 1,800 miles, indented with numerous harbours admirably suited to the manufacture of timber into merchant shapes, and loading on vessels. This timber belt, lying between the 47th and 49th parallels of latitude, will average 25,000 feet of lumber to the acre, most of which is fir, but also abounding in cedar, alder, and maple. The value of the twenty-four saw-mills in this district is estimated to be 5,300,000 dols., with a daily capacity of 1,300,000 feet, at which rate it would require 1,000 years to cut up this forest.-Engineering.

THE INVENTIONS EXHIBITION.-A supplement to the London Gazette, published last week, contains the jury awards-subject to revision-made in the Inventions Division of the International Exhibition at South Kensington. The awards in the Music Division will be published in October. There have been distributed 235 gold medals, 438 silver medals, 515 bronze medals, and 24 diplomas of honour. The following gold medals have been awarded by the Society of Arts on the recommendation of the Juries:-Sir Henry Bessemer, F.R.S., for the invention of Bessemer steel; Percy Gilchrist, for the Thomas-Gilchrist basic process of steel-making; Hathorn, Davey, & Co., for their domestic motor; Samson Fox, for the invention of corrugated iron flues for steam boilers; Crossley Brothers, for the "Otto" gas-engine; Ralph Tweddell, for his system of applying hydraulic power to the working of machine-tools and for the rivetting and other machines which he has invented in connection with that system; Badische Anilin and Soda Fabrik, for their improvements in the manufacture of colouring matters and intermediate products from coal-tar; William Crookes, F.R.S., for his improvements in apparatus for the production of high vacua, and for his invention of the radiometer.

THE Government Astronomer of Hong Kong has published a notice with regard to typhoons, from which it appears that the earliest signs of these phenomena in the China seas are clouds of the cirrus type looking like fine hair, feathers, or small white tufts of wool travelling from east to north, a slight rise in the barometer, clear and dry but hot weather, and light winds. These are followed by a falling barometer, while the temperature rises still further. The air becomes oppressive from increasing dampness, and the sky presents a vaporous and threatening appearance. A swell in the sea, and also phosphorescence of the water, as well as glorious sunsets, are other signs useful to the mariner, who is acquainted with the usual conditions in the locality. When the typhoon is approaching, the sky becomes overcast, the temperature in consequence decreases, the dampness increases, and the barometer falls more rapidly, while the wind increases in force. Nearer the centre the wind blows so that no canvas can withstand it, and the rain pours down in torrents, but there is no thunder and lightning. Still nearer the centre there is less wind and rain, and the sky is partly clear, but the sea is tremendous. This is therefore the most dangerous position. Typhoons may be encountered in any season of the year, but are most frequent in August and September. They appear to originate south-east of the Philippine Islands. In August and September they frequently pass east of Formosa, or travel towards north-west up through the Formosa Channel, or strike the coast of China. Afterwards they usually recurve towards north-east and pass over Japan or across the sea north of Japan, but not with the violence that is characteristic of tropical storms. During the remainder of the year they most frequently cross the China Sea from east to west.

Our Inventors' Column.

SHIPS' SIGNAL LAMPS.

[Patent No. 15,147. 1884.]-This invention, by Mr. Edwin Martin, of 68, West India Dock-road, London, E., is intended as a means of ensuring better light and absolute freedom from being extinguished by the violence of the weather, irrespective of its severity. It is, therefore, entitled to greater consideration for the prevention of collisions at sea, which are too frequently caused through the lights becoming extinguished.

It has two lenses, an outer and an inner, either of which may be coloured; between the two lenses there is a space, about 1 in. wide, for the purpose of admitting a current of air between them, the object being to keep them cool.

The inner lens is fitted inside the body of the lamp, and a shieldplate is so fixed to the lens and sides of the lamp as to prevent any up or down draught coming into contact with the light.

The shield-plate, which is the chief novelty, is fixed to back and sides of the lamp. It is bent conical, and is left open at the top end under the raised top of the lamp.

The outer lens is fitted to a hinged frame, for the more ready convenience of keeping it clean and preventing an accumulation of dirt whereby the full advantage of the light may become unobtainable.

At the bottom of the lamp is a row of air-holes, so constructed as to maintain a clear current of air, and allow it to pass away either top or bottom.

The lamp is proof against being extinguished either by wind or water, without regard to its application.

Colza or petroleum oil may be used for burning, and the method for trimming is similar to that adopted in the ordinary signal lamps now in use.

The body or frame of lamp may be made any size or material.

Trials of Mr. Martin's Lamp have been made with the top open. 1st.-A blast generated by a fan driven by steam power was played on it from every direction; this trial lasted about ten minutes.

2nd. The lamp was run through a trough of water ten feet long, being held under water.

3rd.-Water from a fire-hose was played on the lamp from all directions for about ten minutes, the top being left open. None of these trials produced any effect.

The lamp had been lit about half-an-hour before the trial took place, so that the metal and glass had plenty of time to heat. It must be admitted that by a very simple and inexpensive contrivance, the patentee has accomplished what he claims for itviz :

It cannot be blown out by the wind or put out by water, and is so constructed that the lenses will always keep cool.

These lamps appear to be exceptionally well suited for large or small craft, such as coasters and fishing-vessels that usually carry their lights near the water, as they are not liable to be blown or jerked out by the quick motion of such craft; neither would the lens be damaged or the light affected by sprays or seas going over them.

SLOW FOCUSSING MICROSCOPE ADJUSTMENT. [Patent No. 12,952. 1884.]-This invention of Messrs. Swift & Sons, of 81, Tottenham-court-road, W., consists of a dovetail slide placed parallel to the optical-tube of the instrument; it is lifted by a trigger-shaped lever, and is depressed by means of a spring from above. The lever is moved by a fine thread-milled headscrew, one turn of which moves the optical-tube a 1,000th part of an inch, thus rendering it sufficiently delicate for all kinds of highpower microscopical investigation, and, by lengthening the lever from its fulcrum, any degree of slow motion can be produced. The dovetail slide and the entire mechanism that moves it is in both directions parallel to the line of motion, thus completely obviating the displacement of the object by tilting—a very common defect in all other fine adjustments where the motive power is not central to the said line. As none of the mechanism enters the opticaltube, this is left quite free for the adaptation of the analysing and binocular prisms, which can be brought much closer to the posterior lens of the objective than is usually the case, thus permitting the use of higher powers than when the fine adjustment is fitted within the microscope tube. One great advantage in this form of fine adjustment over the many others is that the distance between the eyepiece and objective is maintained when this movement is in action. Although it is so exceedingly delicate in use, it will resist the strain of adapting either two or four objectives in their double or quadruple piece.

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.

METEORIC DISPLAY.

[1874]-I should be very glad to hear through KNOWLEDGE that other readers noticed the meteoric shower that occurred on Monday evening between 9.15 and 10.40. At the same time a brilliant display of lightning illuminated the sky on the eastern horizon.

All the meteors appeared to diverge from a point just below Cassiopeia in the Milky Way. The brightest fell from the zenith in a S.E. direction, about 9.26. When near the horizon it burst, the particles being of a very intense blue colour and formed a tail like a comet's, which was visible for fifteen seconds.

Several others were seen, but none so bright as the one described.

At 10.40 the sky became overcast with clouds.
Bracebridge, Aug. 10, 1885.

JAS. GRANT.

[The display belonged to the well-known August shower-the Perseids.-R. P.]

METEOR SHOWERS.

[1875]-I should feel much obliged if you would clear up some difficulties in my mind on the subject of meteor showers.

Some years ago I read with the greatest interest a lecture delivered at the Royal Institution, on Feb. 14, 1879, by Mr. G. J. Stoney, F.R.S., on the "Story of the November Meteors." Your articles on meteors in this year's KNOWLEDGE Considerably discount the value of this otherwise most interesting lecture. To account for these meteors which once travelled together, afterwards lengthening into a procession, he conjectures that the November shower was once (in A.D. 126 probably) a cluster close to Uranus, when the individual meteors, being perturbed in greater or less degree, tended to separate, those most attracted lagging behind. Furthermore, he says at p. 9-"As the comet (with a cluster of meteors within it) swept past the planet, its outlying parts would seem to have grazed his surface, and in this way the gas was probably somewhat more retarded than the meteors; and in the centuries which have since elapsed the meteors have gone so much ahead of the comet that they are now treading on his heels, and on the point of overtaking him, while, probably, the gas has again brought together a smaller cluster of the meteors."

In one of your articles you show clearly that this reasoning is quite fallacious, and that, paradoxical as it might seem, the perturbation would have quite a different effect.

My difficulty is mainly this, that while your argument appears quite correct, Mr. Stoney's would seem to accord better with the evidence.

Here are the points I wish cleared up:-1. Is it not a fact that meteor-trains do lengthen out in the lapse of ages, early in their history being condensed in a compact body like the Leonids of November, and finally straggling so much as to be scattered all round their orbits as the Perseids of August?

2. If they do lengthen out, does it not agree better with Schiaparelli's or Stoney's theory than with yours, which, I take it, assigns to each meteor a new orbit, with major axes lying in different directions, the point of perturbation being, the only point common to each orbit?

If so, how would they get away so far from the main body? (I may mention that last year I watched for them after midnight, but as I saw none in half an hour, I went to bed.)

4. Is the following a valid objection to your theory of a meteor'sor rather a meteor-train, being ejected from planets, sun, or stars? Observation or analogy show that all these bodies rotate. If a shower takes two days or two years to fly past a given point, we must presume (unless a lengthening-out happens in transit) that the shower took two days or two years for the process. But if the process did last so long as this, it would be impossible for all the ejected matter to be expelled from the rotating body in the same direction-unless, indeed, the material was discharged from the poles of the rotating body.

The fixed radiant-point question is very interesting, and I hope a good exposition of the subject will appear in Knowledge. MORE LIGHT.

[1. Meteor systems lengthen out. 2. This agrees with my theory at least as well as with Schiaparelli's. 3. The " gem of the ring" of Leonids has passed completely away from the neighbourhood of the earth's orbit. We may, however, be shortly expecting to see some of the meteors scattered in front of the main body. 4. If a shower takes two days or two years now in passing a given point, it by no means follows that the original cluster took that time in starting on the contrary we know the present extension of the flight is greater than of old. Hence this peculiarity implies no objection at all to my theory.

Lastly I may remark that my theory was suggested years after I had examined and described the peculiarities "More Light" touches on, besides a number of others which few of those who just now treat of meteors seem to remember-assuming they ever knew them. My essays, written in the years 1866-71, on the November meteors alone would make a good-sized book.-R. P.]

INVISIBLE SUNS.

[1876]-I was much interested by an article by Mr. Proctor which appeared in KNOWLEDGE a few months ago, pointing out the comparatively small number of orbs which are likely to be inhabited at any one time. It seems to me that the same chain of reasoning leads to the conclusion that the universe must contain many invisible suns-great orbs like our sun, which have cooled down sufficiently to emit no light of their own.

Some of these may probably be in a condition, as regards temperature, permitting of their habitation by living creatures. It is a curious speculation, What forms of life would be found on such a globe, illuminated, as it would probably be, only by starlight?

SUN WORSHIP.

MUSAFIR.

[1877]-If the writer of the letter No. 1835, page 79, in KNOWLEDGE for July 24 of this year will give in KNOWLEDGE the source of his information respecting the sun worshippers of Mexico and Peru who "held dogmas almost identical with Christianity," I shall be extremely obliged. ZETEO.

LIFE IN THE MOON-DEATH OF PLANETS-BLUE SKIES -MOISTURE OF THE ATMOSPHERE-SOLID OXYGENTHE WATERS ABOVE THE FIRMAMENT. [1878]-By referring again to letter 1812, "Hallyards" will find that the remarks contained therein, concerning imaginary men in the moon, are just as applicable to his new example of Uley Bury as they were to the case of the Pyramids, which he has seen fit to lay aside.

Unless "Hallyards" can demonstrate the probability he assumes, the age of life in the moon must have overlapped a period, the exact counterpart of a given period of life on the earth, and yet not have exceeded the present; he may throw back the age of man and his work as many centuries as he pleases without affecting the question in the least.

In the absence of an occasional fact or even probability to guide, it is penetrating far enough into realms of imagination, to picture either an inhabited moon, or a moon never the abode of life, without defining a limit to the civilisation or brain power of the merelyconjectured Lunarians. Furthermore, the wish to compare specimens of human work, lunar and terrestrial, without a comparison of the circumstances giving rise to the work in either case, shows a decided tendency to build "castles in the air."

I must inform "Hallyards" that I do not "contend" for the "man in the moon," my contention is simply that there may have been men in the moon for all he has said to disprove it. There are perhaps more weighty reasons against an inhabited moon than

those advanced by "Hallyards." (By-the-way, I should like to hear a few particulars of “Uley Bury" and H.'s authority for its remote age.)

"There is nothing to show that planets die, so long as they have their sun." Which is (or rather was) the sun of the moon, the earth, or our sun? The earth, I should think; and since the moon's sun has cooled down sufficient to bear life, the death of its planet can be easily understood. What will the earth be like when our sun is cool enough to bear life?

The "positive fact" that northern skies are bluer than those of the "sunny south" needs some slight corroboration.

Walking through a picture-gallery a day or two ago, I could not help noticing how different tints of blue (independent of cloud colour) were characteristic of different latitudes. We are all prone to mistakes ("H." not excepted); but seldom is the fact so exemplified, as in the case of our artists in their endeavour to reproduce nature, if "Hallyards" in this instance be correct.

Once again, "Hallyards' " has supplied me with the argument against himself. A better proof that the amount of aqueous vapour must be greater in warm climates than in cold, I could not have wished than that instanced by the sudden introduction of "French rolls" into this discussion. Because in France, "rolls" and things in general are unusually dry, he concludes that the atmosphere likewise is dry. Will "Hallyards" explain where the moisture of the rolls, &c., has gone? It has simply evaporated, which means, the solvent power of air being raised by an increase of temperature, the water required to saturate it is drawn from wherever water is exposed, be it lake, river, rill, or "roll."

I am asked to "demonstrate that (the atmosphere of) the parched Soudan has more water than the storm-swept Arcades." If the foregoing example is not sufficient, the following figures will explain:

Air absorbs one hundred and sixtieth part of its weight in aqueous vapour at 32°, one-eightieth at 59°, one-fortieth at 86°, summer heat, and a twentieth at 113°, intense heat.

As to solidified oxygen and nitrogen, like the discovery of the conjectural metal hydrogenium, it has been accomplished numberless times within the last twenty years, if every scientific announcement of the fact is to be credited-we have been deceived so often that incredulity is somewhat pardonable. I made the assertion that these gases could not be solidified on the authority of at least half-a-dozen standard Chemistries, but I will not dispute the point, as it is of no moment. I admitted in last letter that all gases might be solidified.

Referring to the "waters-above-the-earth" theory, a scanty glance through the first chapters of Genesis will show "Hallyards that its origin is shrouded in no ambiguity, and we are not even dependent upon the Hebrew records for its exposition; it was an universal idea. ALEX. MACKIE.

[The question of the possibilities of past life in the moon though suitable enough for suggestions, is not one for discussion. We can fancy many things but can establish nothing.-There can be no doubt that there is more moisture usually in the air over hot regions than over cold ones. Oxygen and nitrogen have both been solidified, and by more than one process.-R. P.]

EVOLUTIONISM.

[1879]-So much has been lately written in KNOWLEDGE about the Darwinian theory, that perhaps I also may be allowed to raise a point or two that seem as yet untouched.

I cannot help thinking that the reason why Darwinism is so generally accepted at present is because it is a theory so admirably suited for our present phase of thought. In these days of inventions, of rapid advance in science and in material civilisation, when the ideas of all instinctively turn, whether they will or not, in the direction of the unlimited development of human resources, the notion even of an inexpansible millennium becomes too narrow for us, and in such an age this new evangel of progress could not fail to have an immense following. A century ago, had there been found a historian who could philosophise on history as we do now, and could he have foreseen the enormous strides that have lately been made in science and its application to material resources, he might have been able to predict that a theory of this nature would arise-he might even have laid down some of its main characteristics. The moral to be drawn is this: the more completely a theory is the creature of its age, the more deeply ought it to be distrusted.

Again, it really seems to me that the "struggle for existence" has too much to carry. It appears to be forgotten that slight variations (the only kind admitted) are absolutely and totally ineffective in this struggle because their results are so small. To illustrate: I wear moustaches on my lip which in eating continually get inconveniently into my mouth, but are most ungraceful