184 'ROCHESTER ACADEMY OF SCIEN'CE. [Jan. 9, 



kanies, while the prolonged ridges are termed cskers or osars, excepting 

 their peculiar development in northeastern Iowa, where they are com- 

 posed chiefly of loess or fine silt and have received the name paha, 

 alike whether singular or plural. (') Kames, as thus defined, usually 

 or often constitute an important part of the terminal moraines, and they 

 are also frequent on many other portions of our drift sheet. Eskers 

 are found likewise both in the vicinity of terminal moraines, some- 

 times being evidently of closely contemporaneous origin, and also 

 remote from moraine belts. In length the eskers or osars vary from 

 a mile or less to several miles, and in Maine and Sweden they extend 

 in many continuous series, 20, 50, and even 100 miles or more. Their 

 courses are commonly somewhat crooked, like those of rivers, but in 

 general they run in parallelism with the glacial strire and directions 

 in which the ice-sheet moved and carried its boulders and other drift. 



The structure of the Pinnacle hills esker is well exhibited near 

 its northeast end, near Monroe avenue, and at various places separa- 

 ted only by short intervals, thence westward to Mt. Hope avenue and 

 cemetery, by excavations for the use of its gravel and sand in road- 

 making and masonry. Less than a quarter of a mile south of 

 Brighton, a cut on the northern slope of the east end of the esker, just 

 east of the north to south road (Arbutus avenue), has a depth of 

 about 30 feet and length of some 12 rods. The upper 10 feet are 

 fine gravel and sand, almost levelly bedded, beneath which the remain- 

 der of the section consists of very coarse but distinctly stratified 

 gravel, with a nearly uniform dip of 15" W. S. W. This coarse gravel 

 contains cobbles and rock fragments of all sizes, up to i^ feet in 

 length, packed closely together, their interstices being filled with finer 

 gravel, sand, and very fine silt. About two thirds of all the stones 

 are much water-worn, so as to have rounded forms ; nearly all of the 

 remaining third are somewhat worn, being subangular ; and only 

 about a twentieth part are rather sharply angular, with little or no 

 evidence of attrition in their transportation by the glacial river. Fully 

 half of the small gravel, up to six inches in diameter, are Medina 

 sandstone ; and about a third of the cobbles and masses from 6 to 

 18 inches in diameter are Archaean gneissoid rocks. Only four bould- 

 ers of larger size, none of these exceeding four feet in diameter, were 

 seen in this section. 



Close west of this road, nearly opposite to the foregoing and at 

 a distance of 10 to 30 rods southwest from it, a larger excavation. 



(i.) W J McGee, "The Pleistocene History of northeastern Iowa," in the Eleventh Annua 

 Report of the U. S. Geol. Survey, for 1889-90. 



