NATURE 



[April 22, 1909 



it undergoes in old age, and the parasites that may 

 populate it at various times of life. 



The large number of illustrations, many of them 

 excellently executed, is probably the reason for the 

 large, unwieldy quarto form of these volumes and 

 their considerable price. If the text had been printed 

 in type of the size usually adopted in scientific works, 

 and many of the wholly unnecessary and offensively- 

 coloured illustrations of the nude human figure had 

 been omitted, the book could have been produced in 

 the form of a small and cheap octavo volume. 

 In such a form the mass of valuable and often 

 suggestive information which it contains would have 

 been made available for a much larger body of serious 

 students, to many of whom the present volumes will 

 be inaccessible by reason of their cost. 



G. Elliot Smith. 



TH£ HABITABILITY OF MARS. 

 Mars as the Abode of Life. By Percival Lowell. 

 Pp. xx + 288. (New York: The Macmillan Co.; 

 London : Macmillan and Co., Ltd., 1908.) Price 

 los. 6d. net. 



WHEN a worker in science devotes a considerable 

 portion of his life to a definite piece of research 

 work, and enriches his science with a series of valuable 

 , publications embodying the details of such an inquiry, 

 he renders a good service to mankind at large by 

 expounding the main results of his investigation in 

 general and popular form. 



It is not often that the investigator is able to accom- 

 plish both of these, but in Prof. Lowell we have a 

 .man who is capable of bringing to a successful issue 

 the one form as well as the other. 



The title of the book under review is sufificient to 

 inform the reader as to the lines on which Prof. Lowell 

 has treated the interesting subject-matter concerning 

 the planet which he has made his own. While his 

 chief energ-ies have been devoted to learning as much 

 as possible about Mars when favourably situated, he 

 has by no means ignored the opportunities afforded 

 him of minutely studying the physical features of the 

 other planetary members of the solar system. Such a 

 general survey has thus enabled him to make an 

 interesting comparison of the conditions on Mars with 

 those seen on the other planets, and thus form an idea 

 of the different stages of evolution in a planet's life as 

 represented by members of our system. 



It will be remembered that in the author's work 

 entitled " Mars and its Canals," which was published 

 In the year 1906, he was led to formulate the opinion 

 that Mars was inhabited by beings of some sort or 

 other, which he considered as certain as it was uncer- 

 tain what those beings may be. 



This view was in opposition to that formulated by 

 Dr. Alfred Russel Wallace, who, in his book entitled 

 "Man's Place in the L'niverse," published in 1903, 

 claimed that there were enormous probabilities in 

 favour of the earth being the only inhabited planet of 

 the solar system, and, further, that the probabilities 

 are almost as great against any other sun possessing 

 inhabited planets. 



Since both the above books were published, a very 

 NO. 2060, VOL. 80] 



important fact has been observed which must un- 

 doubtedly alter some of the conclusions drawn. While 

 Dr. Wallace held that Mars had not sufficient mass 

 to retain water-vapour, and that the polar snows were 

 caused by carbonic acid or some other heavy gas, Prof. 

 Lowell was almost convinced that the dark rifts round 

 the caps when they were in the process of melting 

 were caused by water from the melted ice. 



Recent spectroscopic evidence produced by Mr. 

 V. M. Slipher has, however, shown that there is 

 undoubted evidence of water-vapour in the atmosphere 

 of Mars. 



Granting, therefore, the presence of water-vapour 

 in the Martian atmosphere, the observed changes on 

 the planet can be more easily and naturally explained 

 than the assumption of other matter the behaviour 

 and effects of which are not so familiarly known. 

 Thus the seasonal change of colour of the different 

 portions of the planet Mars is readily associated with 

 the melting at the two poles, thus giving rise to the 

 seasonal variability of the canals as exhibited by 

 Lowell's carloiiclics. 



In the book before us the arguments used are in 

 the main to show that Mars can be an inhabited 

 planet, and the canals and oases, according to Prof. 

 Lowell, are proofs that life of no mean order prevails 

 there. 



Thus in his final paragraphs he writes : — 



" Part and parcel of this information is the order of 

 intelligence involved in the beings thus disclosed. Pecu- 

 liarly impressive is the thought that life on another 

 world should thus have made its presence known by its 

 e.xercise of mind. That intelligence should thus mutely 

 communicate its existence to us across the far stretches 

 of space, itself remaining hid, appeals to all that is 

 highest and most far-reaching in man himself. More 

 satisfactory than strange this ; for in no other way 

 could the habitation of the planet have been revealed. 

 It simply shows again the supremacy of mind. Men 

 live after they are dead by what they have written 

 while they were alive, and the inhabitants of a planet 

 tell of themselves across space as do individuals 

 athwart time, by the same imprinting of their mind." 



In the very brief interval of time in the evolutionary 

 history of a planet, when the conditions are such that 

 life in some form or another can exist, that interval, 

 in the case of Mars, is approaching an end. The one 

 great aim and object of the whole of the intelligent 

 minds on Mars is concentrated on making the utmost 

 use of the slowly diminishing water supply, and, as 

 Prof. Lowell finally remarks, " the drying up of the 

 planet is certain to proceed until its surface can sup- 

 port no life at all." 



Our earth, fortunately, is not in such an advanced 

 stage of its own life-history that like measures are 

 necessary, but undoubtedly the time will come when 

 all nations will have to work together to one common 

 end, namely, to survive at all. 



In the volume before us, which may be looked upon 

 as a delightful essay on the birth and development of 

 worlds. Prof. Lowell has presented us with a vein of 

 thought which will appeal to a very wide circle of 

 readers. Technicalities are avoided as much as pos- 

 sible, and when more detailed information is required 

 the notes brought together in the second part of the 

 volume can be referred to. 



