FREEZING. — LIGHTNING. 
153 
Perhaps there are no rocks which are more rap- 
idly decomposed by the agency of frost than quartz 
and trap rocks. These often form perpendicular 
eminences, and, from their fissile texture, are easily 
split into layers. The water, collecting in these 
crevices, expands by freezing, and thus forces the 
rock into fragments, which fall apart on the melt- 
ing of the ice, and accumulate at the base of the 
cliffs from which they have been precipitated, where 
again they are acted upon by the same cause, until 
they are reduced to minute particles. Vast accu- 
mulations from this cause may be seen at the base 
of East and West Rock, New-Haven ; of the Pal- 
isades, on the Hudson; and at Monument Mount- 
ain, in Stockbridge, Mass. ; and, indeed, wherever 
precipitous ledges of rocks are to be found.* 
There is one agent concerned in the destruction 
of rocks to which we have not alluded, and that is 
lightning. That rocks are splintered into fragments 
by this cause, there can be no question, for numer- 
ous instances of this kind have been recorded. Mr. 
Lyell states that " at Funzie, in Fetlar, about the 
middle of the last century, a rock of mica slate 105 
feet long, 10 feet broad, and in some places four 
feet thick, was in an instant torn by a flash of light- 
ning from its bed, and broken into three large, and 
several smaller fragments. One of these, 26 feet 
long, 10 feet broad, and four feet thick, was simply 
turned over. The second, which was 28 feet long, 
17 broad, and 5 feet in thickness, was hurled across 
a high point to the distance of 50 yards. Another 
broken mass, about 40 feet long, was thrown still 
farther, but in the same direction, quite into the sea. 
There were also many smaller fragments scattered 
up and down." 
* Higgins states that the stone of which the colleges at Ox- 
ford are built, is one particularly affected by frost ; and the con- 
r sequence has been the almost entire destruction of the archi- 
tectural beauty of those once elegant buildings. 
