IGt 



♦ KNOAVLEDGE 



[Feb. 27, 1885. 



many millions of cubic miles, its luass so many billions or 

 trillions of tons ; yet these facts are not impressive in 

 themselves. It is only when we consider them in con- 

 nection with what we know about our own earth that they 

 acquire meaning, or, at least, that they have any real 

 interest for us. For then alone do we recognise their 

 bearing on the great problem which underlies all science, 

 — the question of the meaning of the wonderful machinery 

 at work around us ; machinery of which we are ourselves a 

 portion.* 



In suggesting views respecting Jupiter and Mars unlike 

 those which have been commonly received with favour, it 

 is not by any means my purpose, as the reader might anti- 

 cipate, to depart fiom the usual course, of judging the 

 unknown by the known. Although that course is fraught 

 with difficulties, and has often led the student of science 

 astray, it is in such inquiries as the present the proper, one 

 may almost say the only, course. The exception I take 

 to the ordinary views is not based on the fact that too 

 much reliance has been placed on the argument from 

 analogy, but that the argument has been incorrectly em- 

 ployed. A just use of the argument leads to conclusions 

 very different from those commonly accepted, but not lets 

 different from that theory of the universe to which Whewell 

 seems to have felt himself driven by his recognition of 

 the illogical nature of the ordinary theory j-especting the 

 plurality of worlds. 



Let us consider what the argument from analogy really 

 teaches us in this case. 



The just use of the argument fi-om analogy requires 

 that we should form our opinion respecting the other 

 planets, chiefly by considering the lessons taught us by 

 our own earth, the only planet we are acquainted with. 

 Indeed, it has been thus that the belief in many inhabited 

 worlds have been supported ; so that if we employ the 

 evidence given by our own earth, we cannot be said to 

 adopt a novel method of reasoning, though we may be led 

 to novel conclusions. 



The fact that the earth is inhabited, affords, of course, 

 an argument in favour of the theory that the other planets 

 ;ire also inhabited. In other words a certain degree of 

 probability is given to this theory. But we must look 

 somewhat more closely into the matter to ascertaiu what 

 that probability may amount to. For there are all orders 

 of probability, from certainty down to a degree of proba- 

 liility so low that it approaches closely to that extremest 

 form of improbability which we call impossibility. It is 

 well at once to take this logical basis ; for there are few 

 mistakes more mischievous than the supposition that a 

 theory supported by certain evidence derives from that 

 evidence a probability equal to that of the evidence itself, 

 [t is absolutely certain that the one planet we know is in- 

 habited ; but it by no means follows certainly that planets 

 like the earth support life, still less that planets unlike the 

 earth do so, and least of all that every planet is now the 

 abode of life. 



* It lias often seemed to us that a description, by the close 

 observer Dickeus, of (lie fancies of a brain distempered by fever, 

 correspouda with feelinpja which the student of science is apt to 

 experience as the sense of the awful mystery of the universe im- 

 presses itself on his soul; — "The time seemed interminable. I 

 confounded impossible existences with my own identity. ... I was 

 iis a steel beam of a vast engine, clashing and whirling over a gulf, 

 and yet I implored in my own pei'son to have the engine stopped, 

 and my part in it hammered off." Of all the wonders that the 

 student of science deals with, of all the mysteries that perplex 

 him, is there aught more wonderful, more perplexing, than the 

 thought that he, a part of the mighty machinery of the universe, 

 should anxiously inquire into its nature and motions, should seek 

 to interpret tlie design of its Maker, and should be concerned as to 

 his own share in the working of the mysterious mechanism!-' 



A higher degree of probability in favour of the theoi'y 

 that there are many inhabited worlds arises from a con- 

 sideration of the manner in which life exists on the earth. 

 If one could judge of a pur/iose (according to our way of 

 thinking) in all that is going on around us, our earth might 

 teach us to regard the support of life as Nature's great 

 purpose. Earth, water, and air alike teem with life. No 

 peculiarities of life seem able to banish life. As I have 

 said elsewhere, " in the bitter cold within the Arctic 

 regions, with their strange alternations of long summer 

 days and long winter nights, their frozen seas, perennial 

 ice, and scanty vegetation, life flourishes in a hundred 

 different forms. On the other hand, the torrid zone, with 

 its blazing heat, its long-continued droughts, its strange 

 absence of true seasonal changes, and its trying alternations 

 of oppressive calms and fiercely-raging hurricanes, nourishes 

 even more numerous and varied forms of life than the great 

 temperate zones. Around mountain summits as in the 

 depths of the moat secluded valleys, in mid-ocean as in the 

 arid desert, in the air as beneath the surface of the earth, 

 we find a myriad forms of life." Nor is the scene changed 

 when, with the mind's eye, we contemplate the earth during 

 past ages of her history, even to the most remote stage of 

 her existence as a planet fit to be the abode of life. When- 

 ever there was life at all, there was abundant life. For, 

 though no traces remain of a million forms of life which 

 CO existed with the few forms recognised as belonging to 

 this or that geologic era, yet we can infer from the forms 

 of which traces remain that others must have been present 

 which have left no trace of their existence. The skeletons 

 of mighty carnivora assure us that multitudes of creatures 

 existed on which those monsters fed. The great sea- 

 creatures whose i-emains have been found, attest the exist- 

 ence of many races of small fish. The mighty Pterodactyl 

 did not range through desert ai^-rial regions, for he could 

 exist only where many orders of aerial creatures also ex- 

 isted. Of minute creatures inhabiting the water we have 

 records in the strata formed as generation after generation 

 sank to the sea bottom after death, whereas the correspond- 

 ingly minute inhabitants of the land and of tlie air have 

 left no trace of their existence ; yet we can feel no leason- 

 able doubt that in every geologic age, forms of minute life 

 were as rich in air and on the land as in the sea, or as they 

 now are in all three. Of insect life all but a few traces 

 have passed away, though occasionally, by some rare 

 accident, even so delicate a structure as a butterfly's wing 

 has left its record, not only attesting the existence of hosts 

 of insects, but showing that delicate flowers, with all the 

 charms of sweet perfume and variegated colour, existed 

 in those times as in ours. It is no mere speculation, then, 

 but the direct and unquestionable teaching of geology, that 

 throughout the whole time represented by the fossiliferous 

 rocks, life of all kinds was most abundant on our earth. 

 {To ie continued.) 



The School or Sue.mari\e Telegraphy and Electsical 

 E.\G[NEERING. — This school, which we have already had occasion to 

 notice, is still increasing in popularity and utilitv. The managers 

 (llessrs. W. N. Tiddy and W. Lant Carpenter, U.A., B.Sc), have 

 increased the period of tuition from nine to twelve months. In- 

 creased attention is being devoted to telephony, electric lighting, 

 and tlie transmission or distribution of power, and every possible 

 facility is offered to the student to attain the Iiighest possible 

 degree of efficiency. Parchment certificates are awarded to those 

 pupils who, by their industry and application, are able to secure 

 70 per cent, of the maximum number of marks at the final exa- 

 mination to which they are subjectei It is only on behalf of 

 these successful pupils that recommendations for employment are 

 made, hence the recommendation of tlie managers becomes virtually 

 an "Open Sesame " in the hands of zealous embrj-o electricians. 



