A HISTORY OF SCIENCE 



of one species to be the rate of vicissitude in the animal 

 creation throughout the world." 3 



In a word, then, said Lyell, it becomes clear that the 

 numberless species that have been exterminated in the 

 past have died out one by one, just as individuals of a 

 species die, not in vast shoals; if whole populations 

 have passed away, it has been not by instantaneous 

 extermination, but by the elimination of a species now 

 here, now there, much as one generation succeeds an- 

 other in the life history of any single species. The 

 causes which have brought about such gradual ex- 

 terminations, and in the long lapse of ages have re- 

 sulted in rotations of population, are the same natural 

 causes that are still in operation. Species have died 

 out in the past as they are dying out in the present, 

 under influence of changed surroundings, such as al- 

 tered climate, or the migration into their territory of 

 more masterful species. Past and present causes are 

 one natural law is changeless and eternal. 



Such was the essence of the Huttonian doctrine, 

 which Lyell adopted and extended, and with which his 

 name will always be associated. Largely through his 

 efforts, though of course not without the aid of many 

 other workers after a time, this idea the doctrine of 

 uniformitarianism, it came to be called became the 

 accepted dogma of the geologic world not long after the 

 middle of the nineteenth century. The catastrophists, 

 after clinging madly to their phantom for a generation, 

 at last capitulated without terms: the old heresy be- 

 came the new orthodoxy, and the way was paved for a 

 fresh controversy. 



92 



