GLACIAL PHENOMENA OF NORTH AMERICA. 65 



REV. GEORGE FREDERICK WRIGHT read a communi- 

 cation entitled, 



THE GLACIAL PHENOMENA OF NORTH AMERICA AND THEIR 



RELATION TO THE QUESTION OF MAN'S ANTIQUITY 



IN THE VALLEY OF THE DELAWARE. 



(AHSTRACT.) 



THE speaker remarked that since it was his privilege 

 to present to this Society in Dec., 1875, his first paper on 

 the gravel deposits of Eastern Massachusetts, he was glad 

 to appear again before them to report progress and show 

 to what the subject has led the way. 



Upon this map [referring to a map 15x15 ft. which 

 the speaker had prepared] , the extent of the glaciated 

 region in North America is exhibited, and several of its 



o 



most important features delineated. The boundary line 

 of extreme glaciation passes through Long Island, across 

 New Jersey to Bel videre, through northern Pennsylvania, 

 there bends south through southern Ohio, Indiana, and 

 Illinois. On crossing the Mississippi, it sweeps north- 

 westward to the upper waters of the Missouri. 



The whole region above this line is covered, at least 

 in areas, with till a compact clay, bearing pebbles and 

 boulders- which are occasionally scratched. Above this 

 line, also, the rocks show in favorable situations the 

 smoothed and striated surfaces peculiar to glaciated re- 

 gions. 



On passing south from this line, the superficial deposits 

 change, the rocks are not striated, but show solely the ef- 

 fect of disintegrating influences acting from the surface. 



As you see by the arrows, which mark the observed 

 direction of the striae, the ice-sheet radiated from the 

 highlands south of Hudson Bay, moving along the lines of 



ESSEX INST. BULLETIN, VOL. XIII. 6 



