278 SURFACE GEOLOGY. 
shape. Of these the four longer sides are usually striated parallel to 
each other. 
My attention was called to this as a typical shape by examination of 
certain large striated boulders. In 1856, a boulder of red sandstone was 
exhumed in Amherst, Mass., 6¢ feet long, 54 broad, 2% thick, having 
striz upon the four longer sides parallel to each other.* This was de- 
scribed as something unusual. I found in Quebec, a few years later, 
similarly striated boulders somewhat larger; and in the glacier de 
Bossons in Chamouni, at the foot of Mt. Blanc, I noticed the same trape- 
zoidal figures in a very large stone, 40 by 27 by 12 feet in its dimensions. 
It was striated on the same four sides as the others, and had the ends 
rough. It lay just below the ice, with its longer axis parallel to the 
course of the glacier. Since that time I have always observed the shape 
of glaciated stones, and think the majority have the same form with 
these that I have mentioned. Originally rough, and possibly somewhat 
rectangular, they have been both ground down and striated by the slid- 
ing over them of the glacial rasp, or have been themselves fastened into 
the foot of the ice, and ground over other stones and rocks. After miles 
of scouring, the largest boulders might be worn symmetrically to the size 
of pebbles. On scrutinizing the shapes of stones in the till, one can fre- 
quently find various stages of this process preserved. In Derry and 
Salem I noticed a large number 
of flat stones, of which only one 
side had been smoothed. Let the 
circumstances be changed so that 
these boulders be turned over, and 
.the present upper rough side will 
Fig. 58.—GLACIATED STONE, Moutton- be glaciated, and the whole be- 
amet come symmetrical. A few have 
several faces upon them, as if they had been fastened in the paste several 
times. Fig. 58 shows a glaciated stone in Moultonborough, striated in 
the usual way, and also by a second set (0) across the preceding. It is 
30 inches long, 14 thick, composed of trap, and lies by the roadside upon 
a mass of till. 
A more interesting case has been partially preserved in the Hanover 
* American Fournal of Science, ii, vol. xxii, p. 397. 
