GROWTH OF GEOLOGY. 235 



Darwin, and other pioneers who spoke of a progres- 

 sive evolution of plants and animals. The evolution- 

 idea was whispered by many, and a few proclaimed 

 it prematurely on the house-tops. 



The cosmological speculations of Kant and Laplace 

 as to the possible evolution of suns and their sys- 

 tems did not apparently much excite the geologists, 

 but they must have raised some disquieting thoughts. 

 Sir William Thomson's early insistence (1862- 

 1868) on the secular loss of heat from both earth and 

 sun brought the question nearer home, for the con- 

 clusion was inevitable that the present state of affairs 

 could not have lasted forever. 



Without going back to a nebular, mass w^e must 

 at least think of a time wdien the earth was much 

 hotter than now, when the waters of our ocean 

 formed part of a hot atmosphere, and w^e may also 

 look forward to a time when the earth will be 

 much colder than now, and again without an ocean 

 unless it be one of liquid air. In neither of these 

 conditions coiild life, as w^e know it, exist. " Some- 

 where between these two indefinite points of time in 

 the evolution of our planet it is our privilege to live, 

 to investigate, to speculate concerning the antecedent 

 and future conditions of things.'' * This is the evo- 

 lutionist attitude. 



It is interesting, however, to pause to notice a few 

 of the lines of inquiry w^hich led to the transition 

 from Uniformitarian to what may be called Evolu- 

 tionist geology. 



From the early works of Fourier (1820), Poisson 

 (1835), and Hopkins (1839), dowm to the more mod- 

 ern researches of Thomson and Tait and Ilelmholtz, 

 there has been a prolonged attempt to map out the 

 * Sir John Murray, Rep. Brit. Ass., 1899, p. 796. 



