DISCOVERY 



303 



a minute craterlet on the floor became invisible, while 

 a reddish mist extended over a portion of the floor 

 and also over the rampart. After three-quarters of an 

 hour the mist cleared away, and the craterlet again 

 became visible. 



The evidence which Pickering has collected of the 

 existence of some form of vegetation on the lunar 

 surface is pretty strong, if not fairly conclusive. The 

 possibility of the presence of vegetation was mentioned 

 as long ago as 1S5S by De la Rue, while Flammarion 

 suggested it as the explanation of the darkening of 

 the floor of Plato. However, the majority of astrono- 

 mers dismissed the idea as absurd. Unperturbed by 

 the prevailing scepticism, Pickering began as early 

 as 1893 to make close investigation of a number of 

 variable spots, which darkened rapidly after sunrise 

 and faded out towards sunset. A considerable number 

 of these spots have been studied by him, and it is 

 difficult to refute his contention that they represent 

 a rudimentary kind of vegetation springing up and 

 withering during the long lunar day, which is more 

 analogous to our terrestrial year than to our day. 

 Regarding the nature of this vegetation we know 

 nothing. Pickering has pointed out, however, that 

 " lunar vegetation would have two distinct advantages 

 over our own. In the first place, since the force of 

 gravity is less upon the moon, the same leaves or 

 fronds or branches would require but one-sixth the effort 

 to lift and support themselves that would be necessary 

 were they transplanted to our earth. Secondly, since 

 there are no high winds upon the moon, if it were any 

 advantage to plant life to lift itself above the surface 

 of the ground, it could do so with safety, instead of 

 clinging close to the rocks, like our own arctic and 

 antarctic flora." 



It must be admitted that many astronomers hesitate 

 to accept Pickerings conclusions. In a recent lecture. 

 Professor Aitken, of the Lick Observatory, remarked 

 that " further confirmatory observations are desirable 

 before we accept these changes so demonstrated ; and 

 even then we may well hesitate to accept the explana- 

 tions that have been offered." But we must bear in 

 mind that the critics of Pickering's views have devoted 

 no special attention to the surface of the moon, while 

 Pickering is the one prominent observer who, under 

 favourable atmospheric conditions, has studied the 

 moon intensively for over a quarter of a century. 

 Naturally, therefore. Professor Pickering's conclusions 

 must be admitted to carry a great deal more weight 

 than the objections of his critics, however eminent 

 these may be in other branches of astronomy. There- 

 fore we may say, with some degree of confidence, that 

 the balance of evidence is on the side of the view that 

 changes do take place on the moon ; in other words, 

 that the moon is not a dead, but a dying, world. 



The Herd Instinct taken 

 Seriously 



By T. H. Pear, iM.A., B.Sc. 



Professor o/ Psychology in Ihe University 0/ Manchester 



In igoS and 1909 there appeared in the Sociological 

 Review two essays on the Herd Instinct by Mr. W. 

 Trotter. It is fair to say that, whether the reason 

 lay in the unfashionableness of this journal, or the 

 mental resistiveness of the public in 1908, they pro- 

 duced little visible impression upon any but a small 

 circle of workers. Then came the war, and during it, 

 the middle part — " Speculations upon the Human 

 Mind in 1915 " — of the present book.' This essay con- 

 tained a comparison of German with English mentality. 

 To many such an effort seemed foredoomed to failure, 

 " for who," they would ask, " can write an unpre- 

 judiced account of his own nation or that of his enemy 

 at such a time ? " This question, however, is just 

 the one which Mr. Trotter put to himself, and the 

 manner of his answer ; the calm, patient, yet firm 

 way in which he has handled some ugly facts com- 

 mands our profound respect. 



Pointing out that one of the best acid-tests to which 

 any scientific hypothesis may be put is its power to 

 foretell the future, he recorded certain reasoned-out 

 prophecies, knowing that before long events would 

 be forthcoming to confirm or refute them. The 

 reader will be interested in, and perhaps surprised 

 at, the opinion, written in 1915, that even though 

 Germany might represent the conflict to others and 

 to herself as a war of defence, there would not be 

 much fighting on German soil. 



The postscript of 1919, which is the new feature of 

 the second edition, is not only a perfect example of 

 the art of consolidating one's gains without at any 

 moment appearing to say, " I told you so " ; it is per- 

 haps the most sj-mpathetic description and analysis of 

 the post-war weariness, the reasserted segregation of 

 classes (the directions of whose lines of demarcation 

 have probably changed rather less than certain 

 buoyant writers would have us believe), and the 

 sudden deep drop " from the high constancy of spirit 

 by which, throughout the long pilgrimage of war, 

 so many weary feet have been upborne, so many 

 dry lips refreshed." 



It will be interesting to watch for criticisms of this 

 postscript by our professional writers upon poUtical 

 affairs. In the light of Mr. Trotter's account of the 

 mind of the politician one might venture a prophecy : 

 but the reader may be left to formulate his own after 

 he has finished the book. 



' Instincts of the Herd in Peace and War, by \V. Trotter. 

 Second edition, enlarged. (London, Fisher Unwin. 8s. (>d.) 



