THE MOON.*

MR.

R. PROCTOR has in this instance, we think, excelled his previous efforts, and has produced a book not only excellent in character and clear in style, but of a nature to command a large circulation, and to make selenography, from an unknown, an extremely popular pursuit. We know of no book in the whole literature of astronomy which deals so thoroughly with its subject, is so admirably illustrated, and withal so clear in style, as this treatise on the moon. Although the earlier portions treating of the moon's peculiar motions are difficult, yet the difficulty vanishes before even an unmathematical persevering student; and the latter portion of the work is of a character so absorbingly interesting that it is difficult to lay down the treatise without finishing its perusal. We think that considerable credit is to be awarded to Mr. Proctor for his efforts to make the moon's motions intelligible to the general student. He has spared no pains to make the subject completely clear, and he has given such a number of plates containing plans and diagrams, that we feel assured none will feel difficulty in completely understanding even the difficult questions he discusses. But to our mind the most interesting portion of the work is that which relates to the general contour of the moon, and to the manner in which it has been produced; as also to the important question whether there is volcanic action still going on in that portion of the orb which is visible to us. Mr. Proctor gives all the views of those for and against the opinion that volcanic action is taking place, and he sums up as follows:"The only explanation available therefore appeared to be this-that a mass of matter had been poured into the crater from below, and had overflowed the barrier formed by the ring mountain, so as to cover the steep outer sides of the ring. Instead, therefore, of an outer declivity, which could throw a shadow, there appeared to be an inclination, sloping so gradually that no shadow could be detected, the whole surface thus covered with eruptive matter shining with the same sort of light, so that a spot was seen somewhat lighter than the Sea of Serenity, and larger than the original crater." To be sure this explanation may seem rather vague to the reader of this notice, who has not had the work before him, but it really is an admirably clear summary. However, it turns out that it has been shown "by Browning in 1867 that Linné changes remarkably in aspect in a very short space of time, under changing solar illumination; and the inference would seem to be that the supposed changes have been merely optical." It will be found that on every other part of the subject the author is as particular in laying the arguments pro and con before his readers. Altogether Mr. Proctor has given us a book for which our most sincere thanks are due. And to him also, and Mr. Rutherford and the Rev. T. Webb, our gratitude is owing for the magnificent atlas which accompanies Mr. Proctor's book. This contains enlarged copies of Rutherford's splendid photographs,

* "The Moon: her Motions, Aspect, Scenery, and Physical Condition." By R. A. Proctor, B.A., Hon. Sec. R.A.S. London: Longmans, 1873. "The Moon" (three photographs-several maps). By Rutherford and Proctor. Manchester: Brothers, 1873.

representing (in 1ft. by 1ft. size) the full moon and both halves, and a series of maps by Proctor, Webb, and Schmidt, of Athens; a splendid enlarged copy of Beer and Mädler's Map of the Moon; and a couple of admirable lunar landscapes. All these add to the importance of Mr. Proctor's book, and together with it constitute a complete history of our nearest heavenly neighbour.

WE

DARWINISM AND THE ORIGIN OF MAN.*

E are sorry our space does not permit us to notice this very clever and in its second edition-a fact that tells in its favour as being a popular work in Belgium. We cannot, however, see the force of the author's opinions, and we can only account for them on one supposition, viz. that he has had nothing but a book-knowledge of the subject on which he writes. Still, he has combatted the Darwinian side with some cleverness, and his book merits being read by Darwinians, who, we are not disposed to think, will have their opinions seriously modified by its perusal.

* "Le Darwinisme et l'origine de l'homme." Par l'Abbé A. Lecompte, docteur en sciences naturelles. 2ème édition. Paris: Victor Palme, 1873.

419

SCIENTIFIC SUMMARY.

AR

ASTRONOMY.

RRANGEMENTS for observing the approaching Transit of Venus.-We are disappointed to learn that, although the Astronomer Royal has assented to the proposal of the Greenwich Board of Visitors that application should be made to Government for expeditions to survey the sub-antarctic regions, to find additional localities for observing the whole duration of the Transit of Venus in 1874, the application has been so made as almost to ensure failure. It is proposed simply that the Challenger should be commissioned to report on Heard Island (sometimes called Macdonald Island), and that, should the report be favourable, an observing party should be left on that island by the same ship which carries an observing party to Kerguelen Land. This arrangement is altogether inadequate, simply because Macdonald Island is in the same region as Kerguelen Land, and will probably present the same meteorological conditions. It is a serious misfortune for science that the Astronomer Royal, though he has now been forced by the united voice of all the leading astronomers of England (headed by the greatest of them all) to move from the position in which he had intrenched himself, nevertheless moves so slowly and unwillingly as to occasion serious risk of failure. It seems worse than a fault, it is a blunder; since nothing can render less complete his admission of the justice of views he formerly opposed, and his present perversity (we can use no milder term) enforces his opponents to repeat statements which they would willingly leave to be forgotten.

We perceive that Admiral Richards, Hydrographer to the Admiralty, has entered the lists in Sir George Airy's cause, writing to "The Times" in terms implying that Mr. Proctor had considered only the geometrical relations of the matter, while the Astronomer Royal had taken other circumstances, and especially geographical ones, into account. Mr. Proctor's rejoinder was easy and ready. It was actually Admiral Richards himself who most authoritatively indicated, in 1868, the possibility of these very expeditions which he now opposes. He and other eminent naval men urged in very strong terms that which Sir George Airy had urged, the desirability of Antarctic expeditions to view the transit of 1882. Now that Mr. Proctor has shown, and it has been universally admitted, that Antarctic stations would be useful in 1874 only, and much more useful then than Sir G. Airy had mistakenly supposed they would be in 1882, is it not manifest that the opposition to Antarctic expeditions for 1874 can have but one interpretation? Such expeditions would in point of fact stultify the utterances

of the Astronomer Royal in 1868. But whose fault is that? Must science be allowed to suffer merely that a result personally unpleasant to the Astronomer Royal may be avoided?

Dr. Oudemans' Photographs of the Solar Eclipse of December 11-12, 1871.-Lieut-Col. Tennant makes the following remarks on two photographs of the corona taken for Dr. Oudemans by Mr. Dietrichs, at Buitenzorg, in Java:-"These consist of two paper proofs from the original negatives and two transparent enlargements on glass. In the negatives the diameter of the lunar disk is about 3 m.m., so that the equivalent focus of the lens must have been about 41 c.m., or 16 inches. Dr. Oudemans describes it as No. 10 C. by Liesegang, of Elberfeld. The exposure in each case was half a second, and the glass enlargements show that the amount of corona depicted was not very materially less than in the photographs at Dodabetta and Bekul. The Moon's limb is, however, very sharp, and the small negative has borne enlargement to a lunar diameter of 2 c.m., with singularly little loss of definition of the dark edge; which, too, is very free from halation or encroachment from the prominences. In the transparencies sent me, however, there is very much less detail in the corona than in the Indian photographs. The principal thing to be noted is the very complete resemblance of the general form of the corona in the Java photographs and in our Indian ones, though there was an hour of difference in absolute time. I can recognise almost every depression of outline, and the form and relative sharpness of the edges of the southern rift, and even of the less definite northern one, are very markedly similar. I presume no one now believes the corona to be an atmospheric phenomenon; but these photographs show a considerable amount of permanence in its features, and it would be very interesting to compare the original negatives, for which purpose perhaps those of Mr. Dietrichs could be procured."

The Radiation of Heat from the Moon.-Jn his discourse on this subject, at the Royal Institution, on May 30 last, Lord Rosse made the following remarks relative to his recent observations for determining the heat radiated to us by the Moon :

"The observations made during the seasons 1868-9 and 1869-70 were found to follow pretty well Lambert's law for the variation of light with phase. It was found also that a piece of glass which transmitted 80 per cent. of the Sun's rays suffered only about 10 per cent. of the Moon's rays to pass through; thus a large amount of absorption before radiation from the Moon's surface was shown to take place. In the earlier experiments no attention had been paid to the correction to be applied for absorption of heat by the Earth's atmosphere; but, as the apparatus was gradually improved, it became indispensable to determine the amount of this correction before attempting to approach more nearly to the law of variation of the Moon's heat with her phases than had been done in the earlier investigation. By taking long series of readings for lunar heat through the greatest ranges of zenith distance available, a table expressing the law for decrease of heat with increase of zenith distance, closely following that deduced by Seidel for the corresponding decrease of the light of the stars, was obtained. By the employment of this table, the determinations of the Moon's heat at various moments of the lunation were rendered comparable and available for laying down a more accurate "phase-curve" than had

been previously obtained. This curve was found to agree more nearly with Professor Zöllner's law for the Moon's light, on the assumption that her surface acts as if it was grooved meridionally, the sides of the grooves being inclined at the uniform angle of 52° to the surface, than with Lambert's law for a perfectly smooth spherical surface.

"The laws of absorption in the atmosphere, and of variation of heat and light, are indicated in the following abbreviated tables :—

"N.B.—Before entering the atmosphere the Moon's heat = 1.262, so that at the zenith fully th is absorbed before it reaches the Earth's surface.

"N.B.-To compare the heat transmitted by glass with Zöllner's photometric observations (Column V.), the quantities in Column IV. must be multiplied by 5·792.