226 PROGRESS OF SCIENCE IN THE CENTURY. 



invent hypothetical agencies; that we must exhaust 

 the full potency of known and verifiable causes before 

 we admit even the seed of postulating others which 

 are unknown and unverifiable. 



The unifonnitarian view, well expressed by Hut- 

 ton and Playfair, was right when it insisted that we 

 must in our interpretation exhaust the possibilities 

 of actually observable factors, but it was wrong if 

 it assumed that these were necessarily all the factors, 

 or that they had never changed in the rate or amount 

 of their influence. 



In the hands of Lyell (1797-1875) the unifonni- 

 tarian interpretation found its best expression, and at 

 the same time, as many think, signed its own death- 

 warrant. For in spite of the progress of physics and 

 astronomy since the time of Hutton, Lyoll deliber- 

 ately shut out the light of the evolution-idea the 

 thought of a beginning and of an end to the earth 

 which the theory of energy presses home. " He con- 

 sistently refused to extend his gaze beyond the rocks 

 beneath his feet, *nd was thus led to do a serious 

 injury to our science ; he severed it from cosmogony, 

 for which he entertained and expressed the most pro- 

 found contempt, and from the mutilation thus in- 

 flicted geology is only at length making a alow and 

 painful recovery." * 



A reaction from extreme un if ormita nanism was 

 inevitable. It began to be felt that although " Lyell, 

 in his great work, proved that the agents now in 

 operation, working "with the same activity as that 

 which they exhibit at the present day, mifjkt produce 

 the phenomena exhibited by the stratified rooks, 



W. J. BolUn, IVm. AddreM, Sao. C, *. r* Au., 1000; 

 Naturt, Sept. 13, 1VOO, p. 481. 



