SCIENTIFIC USE OF THE IMAGINATION. 129 



of biological succession. Guided by analogy, in his 

 ' Origin of Species ' he placed at the root of life a 

 primordial germ, from which he conceived the amazing 

 variety of the organisms now upon the earth's surface 

 might be deduced. If this hypothesis were even true, 

 it would not be final. The human mind would in- 

 fallibly look behind the germ, and however hopeless the 

 attempt, would enquire into the history of its genesis. 

 In this dim twilight of conjecture the searcher welcomes 

 every gleam, and seeks to augment his light by indirect 

 incidences. He studies the methods of nature in the 

 ages and the worlds within his reach, in order to shape 

 the course of speculation in antecedent ages and 

 worlds. And though the certainty possessed by experi- 

 mental enquiry is here shut out, we are not left entirely 

 without guidance. From the examination of the solar 

 system, Kant and Laplace came to the conclusion that its 

 various bodies once formed parts of the same undislo- 

 cated mass ; that matter in a nebulous form preceded 

 matter in its present form ; that as the ages rolled away, 

 heat was wasted, condensation followed, planets were 

 detached ; and that finally the chief portion of the hot 

 cloud reached, by self-compression, the magnitude and 

 density of our sun. The earth itself offers evidence of a 

 fiery origin ; and in our day the hypothes^f^ffi 

 Laplace receives the independent countenance of 

 trum analysis, which proves the same fsiibs^ayc^e fy f 

 common to the earth and sun. - * *i S J J* 1 



Accepting eome such view of the construction^ pair _ * 

 system as probable, a desire immediately arises to^iiW * 

 nect the present life of our planet with the past. We 

 wish to know something of our remotest ancestry. On 

 its first detachment from the central mass, life, as we 

 understand it, could not have been present on the earth. 

 How, then, did it come there : The thing to be encou- 



TOL. n. K. 



