SEMICIRCULAR MARGINAL MORAINES. 341 



In tlie northwest quarter of section 28 and the west part of section 21, 

 Medford, the highest shore-Hne of Lake Agassiz is very distinctly marked, 

 at 1,183 to 1,185 feet, by being the upper edge of a flat slope of till, proba- 

 bly with scanty deposits of gravel and sand, which sinks 20 to 30 feet in 

 the next half mile eastward. Farther east, for the width of 3 or 4 miles 

 across the Elk Valley, tlie surface elevation is 1,1 GO to 1,125 feet. 



Just west of this shore-line a knolly belt of morainic drift, bearing a 

 marvelous profusion of bowlders, occupies a width of 25 to 50 rods, gener- 

 ally forming a single series of hillocks rising 15 to 30 or 35 feet. These 

 are strewn with bowlders of all sizes up to 5 feet and rarely 8 feet in 

 diameter, so plentiful that they cover a third or even half of the surface. 

 A few masses of limestone were observed, but fully 99 per cent of the 

 bowlders are Ai-chean granite and gneiss. This is the most eastern portion 

 of a semicircular moraine which appears to have been accumulated on the 

 eastern boundary of a lobe of the ice-sheet during a pause in its retreat. 

 From sections 21 and 28, Medford, this moi'aine continues, with nearly the 

 same features, south and southwest to the southeast quarter of section 32, 

 and thence west-southwest by Pilot Knob, in the northwest quarter of 

 section 5, Elkmount, to the west side of section 1, township 154, range 57, 

 and perhaps beyond. Its hills and knobs rise 25 to 75 feet abo\'e the gen- 

 eral level of the adjoining smoothly undulating till, their tops being 1,250 

 to 1,300 feet above the sea. To the north, northwest, and west it reaches, 

 with similar development, in a great curve convex to the northeast, along 

 an extent of 5 or 6 miles, to a cluster of prominent morainic hills rising 50 

 to 75 feet, situated in sections 2 and 3, Cleveland. This moraine matter 

 was doubtless englacial ; among its multitude of both large and small rock 

 fragments a half hour's search failed to discover any marked with strise or 

 having faces planed by glaciation. On the west the area inclosed by this 

 curving moraine is very smooth, only slightly undidating till, at 1,185 to 

 1,250 feet, ascending slowly westward. 



Another distinct morainic series, similar in its very knolly contour, in 

 its material (excepting a larger proportion of gravel, half of which is the 

 Cretaceous shale before described), and in the great abundance of bowl- 

 ders, nearly all granitic, branches from the preceding in the north part of 



