166 Mr. Kendal’s account of the Dighton rock. 
top or back shelves, in irregular ledges and fractures, from its sum- 
mit to the surface of the soil, giving a thickness, which increases, in 
the descent, from one inch to perhaps six feet. The base of the 
rock, at the northeast angle, is partly above, and partly incumbent on 
the surface of the ground ; and, with respect to the remaining and 
more considerable portion, is sunk to a small depth. 
As to colour, the rock, to speak generally, is of a purple red. To 
describe it more particularly, the face, as low as rather more than a 
foot from its summit, has a dark tint, of the hue mentioned. Below 
this is a region of a much lighter tint ; and toward the base is anoth- 
er, somewhat green. The internal colour of the rock, which isa 
light grey, no where appears, except where laid bare by recent fra¢- 
ture. ‘The several colours, the diversity of which forces itself upon 
the eye, are bounded horizontally ;- and are occasioned by the differ- 
ence of the periods of time, during which the parts of the rock are ex- 
posed to the air. The summit, which is first abandoned by the wa- 
ter, and last covered again, is purple; the middle region is less act- 
ed upon by the oxygen of the atmosphere, and the lowest is most fa- 
vourable to the growth of the byssus. | Were the rock beyond the 
reach of the tide, its surface would be grey, like that of others, of the 
same stone. 
On Dpreching the rock for the first time, I suffered no eae 
pointment ; my respect for it was not lessened, but increased ; and 
in particular I was greatly struck with the regularity of its figure. 
Three of the sides, as I have already described, are uniformly inclin- — 
ed, whence it proceeds, that the breadth of the face, which, at the base 
- line, is eleven feet seven inches, is diminished, at the height of four 
feet, to ten feet three inches. Thetwo ends; though fashioned to this 
general figure, are indeed very uneven; but the face, near the summit, 
is as smooth as the saw could leave it, and, beneath, as much so #8 
