GLACIAL DRIFT. 255 



Mr. Joseph Dow, of Hampton, says a measurement of the bluff in 1875 

 showed that a length of one rod at the point had disappeared since 1826; 

 and his impression is that a prominent stone, called Gunning Rock, near 

 the end of the boulders, is farther removed from the bluff now than it 

 was forty years since. 



A view of this bluff from either side near the end shows finely the 

 distinction insisted upon in this report between the lower and upper till. 

 The sides of the bluff meet 

 at the end, making a sharp 

 edge, which dips towards the 

 east at an angle of 60°. Fig. 



54 is copied from a photo- 



, u- -u u 4.-U ■\- Fig. 54. — Section OF Boar's Head. 



graph, which shows the line * ^ 



between these divisions as plainly as in nature. The upper part has 

 been broken away near its end, but its depth is nearly uniform over 

 the whole plain, about ten feet, or a little less, at the end. This has its 

 usual reddish-yellow in distinction from the bluish cast of the lower till. 

 It is ferruginous, comparatively loose in texture, and contains rough 

 stones, rarely any that have been striated, and the material is chiefly 

 the slates found in place two or three miles distant. Being easily 

 crushed, the upper till contains an unusual proportion of earth. Its 

 resemblance to the upper till of Portland, Me., is obvious. The lower 

 thirty-five feet of till is composed of very compact, gritty earth, slightly 

 clayey, containing numerous smoothed and striated boulders, from grains 

 of sand to fifteen feet in length. Many of the stones are in the condi- 

 tion of unstable equilibrium. The uncovering of the boulders by wash- 

 ing enables us to learn their nature, and refer them to their probable 

 source. A careful description of the different kinds observed here 

 will illustrate the origin and dispersion of all the boulders along the 

 sea-shore. The most abundant rock is sienite, boulders 12 and 15 feet 

 in length occurring occasionally. Those 6 feet long are common. They 

 are all glaciated, but many have been smoothed since falling out of the 

 bank by the waves. It is gray with a considerable sprinkling of white. 

 I will group the boulders according to size. Of those about six feet in 

 length are sienite, gneiss, trap, Pawtuckaway sienite, granite with blue 

 feldspar, such as occurs in ledges at Frost's Point in Rye, crumpled 



