402 . PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 



an infinitesimal rate of geological changes that Professor Penck 

 should make bold to assign an age of 100,000 years to the 

 palaeolithic implements found in a cavern in Wildkirchli, in the 

 Canton of Appenzell, Switzerland. In reaching this conclusion 

 he estimates the post-glacial period as 30,000 years and that the 

 advance of the ice of the Wurm or Wisconsin period 1,000 feet 

 below the level of the cave, and its continuance and retreat 

 represent periods of 30,000 years each. That this calculation 

 and others like it are purely theoretical without any basis of 

 observation is evident from facts which are now well known. 

 As to the rapidity with which glacial changes may take place 

 it is sufficient to point to the known retreat of the ]\Iuir Glacier 

 during the past thirty years. In 1886 when I made the first ex- 

 tended observation of the Muir Glacier in Alaska, the position 

 of the front was established beyond cjuestion by the photographs 

 which I obtained at that time. The front of the glacier was 

 fully one mile wide, the height of its precipitous face above the 

 inlet into which it was projecting was 300 feet, and the depth 

 of the water as near as it could be safely sounded was 700 feet, 

 showing thus a precipitous ice front a mile wide and 1000 feet 

 thick pushed forward into the inlet by the united force of nine 

 confluent glaciers coming dowai from the rear. In 1909, twenty- 

 three years later, the Canadian surveyors found that the front 

 of the Muir Glacier had retreated seven miles and a half, and 

 that its surface had been lowered 700 feet by melting. Here, 

 therefore, is an actual retreat of a living glacier in a cjuarter of 

 a century exceeding in amount that of the Alpine glacier for 

 which Professor Penck would demand 30,000 years ; and that 

 this is not merely temporal and local appears from the evidence 

 which I have adduced and which Professor Reid and the late 

 Professor Russell (the only geologists who have given attention 

 to the evidence) consider ample, that 100 years before my visit, 

 when Vancouver explored the coast, a confluent glacier filled 

 Glacier Bay and extended its front twenty-five miles beyond that 

 of Muir Glacier as it was in 1886, and that the thickness of 

 the glacier in the upper part of the bay was then 3,000 feet-. 

 The neglect of such facts as these by European glacialists in 



