228 Original Articles. [April, 



in the fervid tropics, as well as in regions of almost perennial frost, 

 in ocean depths so great as to be impervious to the faintest ray of 

 light, and where the pressure of superincumbent water equals a ton- 

 and-a-half on the square inch, as well as in the highest and most 

 attenuated regions of the atmosphere attained to, living beings abound. 

 While yet others, by adding to their knowledge of the present univer- 

 sality of life that of its equal extension during the measureless ages of 

 the past, have had the conviction forced on them that it is always and 

 everywhere co-existent with the conditions fitted for its maintenance. 

 For Geology, leaving the fair face of the green Earth and proceeding 

 step by step down towards her awful foundations, points out the 

 evidences of many a world long since passed away, with physical con- 

 ditions differing often from those which prevail now ; while, at the 

 same time, she lays open the silent tombs of innumerable and strange 

 creatures, to whose organizations such conditions were most minutely 

 adapted. And yet, after having descended into the regions of an 

 immeasurable antiquity, she is obliged to confess her inability to 

 reach the beginnings of life on the Earth, admitting that, for aught she 

 can tell, as extensive an animal and vegetable series might have 

 existed previous to, as since, those earliest traces which she has yet 

 discovered. For every new revelation serves but to strengthen the 

 probability that the entire series of rocks is passing through a cease- 

 less cycle of change, and that granite itself may be but the extreme 

 term of a metamorphism, that by its intensity has obliterated all ves- 

 tige of organisms with which it might once have abounded. Certain 

 it is that the Histiodermas and Oldhamias of the Cambrian period have 

 lately been proved to be recent compared with the incalculably more 

 remote Polyzoa and Foraminifera brought to light in the lower rocks 

 of the Laurentian series, which, in their turn, will probably -be shown 

 to be as far removed from organisms of an earlier period yet to be 

 discovered. 



Although, however, life is so widely diffused, it must be admitted 

 that so far as we are cognizant of it, it cannot exist in the absence of 

 certain conditions. Whether other forms, of which we know nothing, 

 may do so, is an irrelevant inquiry. 



The question to determine then is, whether such conditions exist 

 on other planets : and to what is known of the physical constitution 

 of these, we shall accordingly direct attention, passing by, as of too 

 uncertain a nature for our present purpose, all speculations on Cosmo- 

 gony, or on the probability of the sun's being a variable or a nebulous 

 star or member of a binary system, &c. To begin with elementary 

 constitution — this may fairly be concluded to be similar in all the 

 members of the solar system, for since iron and many other elements 

 are proved by spectrum-analysis to be present in the Sun, and by 

 direct chemical processes to form part of those small bodies which as 

 meteors occasionally strike against the Earth ; and since there can be 

 no possible reason why such elements should be found in these dis- 

 tinct members of the series, and yet be excluded from the rest, the 

 only fair conclusion is, that they enter into the composition of Venus, 

 Jupiter, and the other planets also. Moreover, the study of meteorites 



