PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 307 



puting the age of the earth, and said: "The scale of geological 

 time remains in great measure unknown." 



From the thickness of sediments, and the rate at which 

 rivers are making deposits, Charles D. Walcott in 1893 reckoned 

 the lapse of time since the beginning of the Archean to be 90 

 million years. 



Professor John Joly in 1899, from computations of the 

 quantity of sodium in the oceans and their annual accession of 

 sodium, stated the probable age of the earth to be from 90 to 

 TOO million years. 



Students of biology have preferred a great length of time 

 for the complex results of evolution. The estimates made by 

 physicists, chemists, and some geologists appear inadequate to 

 them. 



Since the discovery of radium, and a more general investi- 

 gation of radio-active minerals and derivatives from radium, the 

 evolutionists have taken hope. No line of investigation has been 

 so profligate with time as that concerning radio-activity. John 

 Allen Harker. the British physicist, .says, "a study of the various 

 radio-active elements contained in minerals and rocks has shown 

 that it is possible, in certain favorable cases, to calculate directly 

 their ages in years." Thus calculated, the Archean rocks are 

 from one billion to one billion, six hundred million years old. 



Over a hundred years ago, Hutton, speaking as do the poets 

 and the prophets in science, asserted that geologic time had "no 

 vestige of a beginning, no prospect of an end." 



Theories of Earth-Origin. Twenty-five years ago one sel- 

 dom heard any question raised about the satisfactoriness of the 

 nebular hypothesis. More recently certain variations in this hy- 

 pothesis have been proposed, but the fundamentals of the La- 

 placian theory have place in all these restatements. Necessarily, 

 modifications should follow upon the findings of the spectro- 

 scope and photograph-attachments of the large telescopes, in- 

 struments that were scarcely dreamed of in the day of the French 

 savant. 



Among the contributions made to geology since the organi- 

 zation of this Academv none is greater than that of T. C. 



