Wads worth.] 172 [April 16, 



and modern arrow-release, defining four principal types, North 

 American, Indian, Saxon, Asiatic and Malay, each showing some 

 variety. 



Dr. Hagen read a paper on the Hessian fly, showing from the 

 records of the American Philosophical Society, that the fly bore 

 this name before the Revolution. 



General Meeting, April 16, 1884. 



Ex-President, Mr. T. T. Bouve in the chair. 

 The following paper was read : 



ON THE RELATION OF THE " KEWEENAW AN SERIES" TO THE 

 EASTERN SANDSTONE IN THE VICINITY OF TORCH LAKE, 



MICHIGAN. 



BY M. E. WADSWORTH. 



At the present time it is well known that in their typical condi- 

 tion the copper-bearing rocks of Keweenaw Point consist of a se- 

 ries of lava-flows, sandstones, and conglomerates, piled one above 

 the other and dipping in a northwesterly direction. 



On the eastern and western sides of the series the fragmental 

 rocks are most abundant, while in the central portions the lava 

 flows are the predominating rocks, which oftentimes followed one 

 another without any intervening conglomerate. Wherever the lava 

 poured over the earlier detrital rock it baked and indurated it, while 

 in every case the conglomerates and sandstones are found to be 

 laid down on the eroded surface of the underlying lava flow, 

 whose debris is seen mingled with the old rhyolitic, trachytic, and 

 granitic material of which the conglomerate is chiefly composed. 

 This alternating action of sea and lava went on from the beginning 

 to the end of the series, the relative proportion of the detrital ma- 

 terial to the lava depending upon the rapidity of the succession of 

 flows. There was thus produced between every flow and between 

 each flow and its underlying and overlying rocks complete uncon- 

 formability the same as everywhere exists when eruptive rocks reach 



