1875.] 133 [Osten Sacken. 



retreating ice sheet, and give no proof of the condition during the 

 time of its widest extension. 



I should say that I have attentively considered the theory so ably 

 presented by Mr. James Croll, -wherein he seeks to explain the move- 

 ment of glaciers by the successive melting of molecules of water in 

 the passage of heat through the ice. I am not prepared to deny that 

 it may account for the motion of local glaciers, but deem it quite in- 

 sufficient to show us how the ice movement could carry the snow 

 formed a thousand miles north of the Ohio down to that river. 

 Moreover, as I before stated, I am satisfied from the paucity of the 

 moraine matter in southern Ohio and the neighboring region, that 

 the movement had no such continuity as leads to the formation of a 

 terminal moraine of a local glacier. 



When the Humboldt glacier, and the other ice sheets of Green- 

 land, come to be studied with care, I am inclined to believe that the 

 great streams of water which issue from beneath them will be found 

 to owe their origin not alone to surface- melting, but also to the action 

 of pressure-melting, and the melting from the passage of heat from 

 the earth's interior into the ice mass. 



October 6, 1875. 



Vice-President, Mr. S. H. Scudder, in the chair. Thirty- 

 two persons present. 



The following papers were read : — 



Note on some Diptera from the Island Guadalupe (Pa- 

 cific Ocean), collected by Mr. E. Palmer. By C. R. 

 Osten Sacken. 



I deem it my duty to place on scientific record a notice of 

 some Diptera from a very unfrequented locality, the Island Guada- 

 lupe, situated in the Pacific Ocean, two hundred and twenty-five 

 miles southwest of San Diego. They were collected by Mr. E. 

 Palmer, who spent there some time in the spring of 1875, on scien- 

 tific duty. These specimens were not pinned, but preserved dry in 

 pill boxes. I pasted them on slips of cardboard, stuck upon pins 



