306 PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 



face. A similar inference has been drawn from wide-spread 

 glaciation. Both deductions are rather broad generahzations. 



Since 1890 there has been a tendency in these matters to 

 seek the concrete and specific. Wherever possible more exact 

 methods have been applied to the hazy interpretations of the 

 past. This application is limited, for the present at least, to 

 the recent geologic past, and the corroboration of human history, 

 wherever possible, adds welcome conviction. Thus is the field 

 exceedingly limited. However, encouraging results have been 

 secured particularly through the work of Ellsworth Huntington 

 in a study of strand lines, and of the growth made by very old 

 trees, the sequoias; the latter respond to, and, in their rings of 

 seasonal growth, register the conditions of moisture ; the former 

 register variations in the level of water bodies in inland basins. 

 Quite recently, Mr. Huntington is attempting to correlate the 

 precipitates of desiccating water with the other two lines of evi- 

 dence. 



This type of investigation is producing results which accord 

 with the deductions made by the paleontologist from the ex- 

 panding, dwarfing, or disappearance of faunas ; it throws light 

 on the origin of gypsum and other locally deposited salts ; and 

 lielps to elucidate several stratigraphic features. 



The Age of the Earth. When one arrays the estimates of 

 this sphere's antiquity, made by workers in various phases of 

 science, he must conclude that mother earth is either a coy' 

 maiden, an indifferent matron, or a gibbering old woman. The 

 margin of safety in these guesses is about one billion years. 



In 1862 Lord Kelvin, studying the thermal conductivity of 

 the sphere, decided that the earth is at least 20 million and not 

 over 400 million years old. After an interval of 35 years he 

 amended these figures somewhat and stated, in concurrence with 

 Clarence King's assertion, that about 24 million years ago the 

 earth was a molten mass. 



Sir George Darwin in 1886 had urged the wisdom of con- 

 sidering "Theories which appear to demand longer periods of 

 time than those which now appear allowable." Ten years ago 

 he suggested again that the physicists may be in error in com- 



