Feb. 27, 1SS5.] 



♦ KNOWLEDGE ♦ 



163 



F 



-^JL V^ AN ILLUSTRATED 



^MAGAZINE OF SCIENCE 



PLAINLYWORDED-EXACTLYDESCRIBED 



LOXDOX: FRIDAY, FEB. 27, 1885. 



OOKTKNTS OF No. 174. 



PACE 



Life in Other ^VjjrMs. By R. A. , 



Proctor .'. ItiJ 



The KalermU. H. By Edward 



Clodd Ho 1 



Optical Reoreations. {XilHt.) By j 



F.R.A.S IGO 



Needed Star-Surveye. By R. A. 



Proctor H-r 



Electric Light on the Brightoa Kail* 



way. {IllHf.) By W. SHdro ... ItW 

 Thought and Language. IV. By 



Ada S. Balliii 170 



Subterranean Woods 171 



Short Sight. By John Browning... 171 | 



Rambles with a Hammer. By \V. 



J«rome Harrison 173 



Forms of Leaves. By Sir John 



Lubboclc 173 



Ftto«of thoSky. By F.R.A.S 174 



First Star Leasuns. (TTifh Map.) 



By R. A. Proctor 17-1 



Editorial Gossip 175 



Keview3 177 



Correspondence : ETolution cersiis 



Natural Sslection— Miud and 



Body — Falliicyof Materialism, Ac. 17S 



Our Inventors' Column 183 



Our Chess Colomn 184 



LIFE IN OTHER WORLDS. 

 Br Richard A. Proctor. 



SO far back as 1869, I had begun to regard doubtfully 

 the theory that all the planets are the abode of life. 

 The careful study of the planets Jupiter and Saturn had 

 shown that any such theory regarding these planets is alto- 

 gether untenable. The great diflerence between them and 

 the members of the smaller planetary family of which our 

 earth is the chief, suggested that in truth the major planets 

 belong to another order of orbs altogether, and that we 

 have as much or as little reason for comparing them to the 

 Eun as for comparing them to the earth on which we live. 

 Xeverthfless, in the case of Venus and Mar.s, the features 

 of resemblance to our earth predominate over those of 

 dissimilarity ; and it was natural that, while rejecting the 

 theory of life iu Jupiter or Saturn as opposed to all the 

 available evidi-nce, I should still consider the theory of life 

 in Mars or Venus as at least plausible. Ideas on such 

 subjects are not less tenacious than theories on matters 

 more strictly scientific. Xot only so, but the bearing of 

 newly-recognised facts on long-entertained theories is not at 

 once recognised even by those most careful to square their 

 opinions accordiug to the evidence they are acquainted 

 with. Again and again it has happened that students of 

 science (in which term I include the leaders of scientific 

 opinions) have been found recording and explaining in one 

 chapter some newly-recogaised fac", while in another 

 chapter they have described with approval some old theory, 

 in total forgetfulness of the fact that with tlic new dL- 

 covery the old theory has become altogether untenable. 

 Sometimes the incongruity is not recognised until it has 

 been pointed out by others. .Sometimes so thoroughly do 

 our prepossessions become "Vione of our bone and flesh of 

 our flesh " that even the clearest reasoning does not prevent 

 the student of science fn.m combining the acceptance of a 

 uewly-discoverfd fact with continued belief in a theory 

 which that fact entirely disproves. Let the matter be 

 explained as it may, it was only gradually that both the 

 Brewsterian and Whewellite theories of life in other 

 worlds gave place in my mind to a theory in one sense 



intennediato to them, in another sense opposed to both, 

 which seems to accord belter than either witli what we 

 know about our own earth, about the other members of the 

 solar system, and about other suns which people space. 

 What 1 now jiropose to do is to present this theory as 

 specially illustrated V)y the two ))lanets which now adorn 

 our skies at night, and by the ruddy but at present invisible 

 Mars. 



But it may be asked at the outset, -whether the 

 qviestion of life in other worlds is worthy of tho attention 

 thus directed to it. Seeing that we have not and can 

 never have positive knowledge on the subject, is it to be 

 regarded as, in the scientific sense, worthy of discussion 

 at all ? Can tho astronomer or the geologist, the phy- 

 sicist or the biologi>t, know more on this subject than 

 those who have no special knowledge of astronomy, or 

 ''eology, or physics, or biology 1 The astronomer can 

 say how largo such and such a i)lanet is, its average 

 dei'Sily, tha length of its day and its year, the light- 

 reflecting qualities of its surface, even (with tho physicists' 

 aid) the nature of the atmosphere surrounding it, and so 

 on ; the geologist can tell much about the past history of 

 our own earth, whence we may infer the variations of 

 condition which other earths in the universe probably 

 undergo ; the physicist, besides aiding the astronomer in 

 his inquiries into the condition of other orb.s, can determine 

 somewhat respecting the physical requirements of living 

 creatures; and the biologist can show how the races 

 inhabiting our earth have gradually become modified in 

 accordance with the varying conditions surrounding them, 

 how certain ill-adapted races have died out while well- 

 adapted races have thriven and multiplied, and how matters 

 have so proceeded that during the whole time since life 

 began upon our earth there has been no danger of the 

 disappearance of any of the leading orders of living crea- 

 ture.?. But no astronomer, or geologist, or physicist, or 

 biologist, can tell us anything certain about life in other 

 worlds. If a man possessed the fullest knowledge of all 

 the leading branches of scientific research, he would remain 

 perfectly ignorant of the actual state of affairs in the 

 planets even of our own system. His ideas about other 

 worlds must still be speculative ; and the most ignorant 

 can speculate on such matters as freely as the most learned. 

 Indeed the ignorant can speculate a great deal more 

 freely. And it is here, precisely, that knowledge has the 

 advantage. The student of science feels that in such 

 matters he must be guided by the analogies which have 

 been already brought to his knowledge. If he rejects the 

 Brewsterian or the Whewellite theory, it is not because 

 either theory is a mere speculation for which he feels free 

 to substitute a speculation of his own ; but because, on a 

 careful consideration of the facts, he finds that the analogies 

 on which both theories were based were either insufficient, 

 or were not correctly dealt with, and that other analogies, 

 or these when rightly viewed, point to a ditferent con- 

 clusion as more probable. 



Nor need we be concerned by the consideration that 

 there can bo no scientific value in any conclusion to which 

 we may be led on the subject of life in other worlds, even 

 thouoh our method of reasoning be so far scientific that 

 the argument from analogy is correctly dealt with. If we 

 look closely into the matter, we shall find that as respects 

 the "reat purposes for which science is studied, it is as 

 instructive to think over the question of life in other world ; 

 as to reason about matters which are commonly regarded as 

 purely scientific. It is scientific to infer from obstrvations 

 of a planet that it has such and such a diameter, or such 

 and such a mass; and thence to inftr that its buifaco 

 contains so many millions of square miles, its volumes f.o 



