130 EVOLUTION. GENETICS, AND EUGENICS 



ON THE LAPSE OF TIME DURING WHICH EVOLUTION IS BELIEVED 



TO HAVE TAKEN PLACE 



"Independently of our not finding fossil remains of such infinitely 

 numerous connecting links [referring to the objection that all steps in 

 the evolution of modern types should be revealed in the fossils], it 

 may be objected that time cannot have sufficed for so great an amount 

 of organic change, all changes having been effected slowly. It is 

 hardly possible for me to recall to the reader who is not a practical 

 geologist, the facts leading the mind feebly to comprehend the lapse 

 of time. He who has read Sir Charles Lyell's grand work on the 

 Principles of Geology, which the future historian will recognize as 

 having produced a revolution in natural science, and yet does not 

 admit how vast have been the past periods of time, may at once close 

 this volume. Not that it suffices to study the Principles of Geology, 

 or to read special treatises by different observers on separate forma- 

 tions, and to mark how each author attempts to give an inadequate 

 idea of the duration of each formation, or even of each stratum. We 

 can best gain some idea of past time by knowing the agencies at work, 

 and learning how deeply the surface of the land has been denuded, 

 and how much sediment has been deposited. As Lyell has well 

 remarked, the extent and thickness of our sedimentary formations are 

 the result and the measure of the denudation which the earth's crust 

 has elsewhere undergone. Therefore a man should examine for him- 

 self the great piles of superimposed strata, and watch the rivulets 

 bringing down the mud, and the waves wearing away the sea-cliffs, in 

 order to comprehend something about the duration of past time, the 

 monuments of which we see all around us." — Charles Darwin, Origin 

 of Species. 



"In 1862," says Schuchert, 1 "the physicist, Lord Kelvin .... 

 held that as our planet was continually losing energy in the form of 

 heat, the globe was a molten mass somewhere between 20,000,000 and 

 400,000,000 years ago, with a probability of this state occurring about 

 98,000,000 years ago. Finally in 1897 he concurred in Clarence King's 

 conclusion that the globe was a molten mass about 24,000,000 years ago. 

 Both of these conclusions, however, were wrought out under the Lap- 

 lacian hypothesis, and now many geologists hold that the earth never 

 was molten. While geologists have not been able to fit their evidence 

 into so short a time, they have ever since been trying to keep their 



1 C. Schuchert, Text-Book of Geology, Part II, Historical Geology (t9is). 



