No. 161.] 
Ill 
parallel with each other. The width of the slide is about 40 rods; 
its extent up the mountain is not far from half a mile, and is yearly 
increasing by the falling of unsupported matter. Down these clefts 
a small stream dashes with some violence, and it may possibly be 
the case, that slides generally occur in those places where there are 
springs, which had not found an outlet previous to the sliding down 
of the earth and stone. On the face of these cliffs there project both 
a bed of the protoxide of iron and limestone, running parallel to each 
other, as far as the iron continues in view. We call them beds, 
but they appear like veins which have been forced up from be- 
neath. The limestone is the coarse crystalline variety, and gene- 
rally white. For some distance by the side of the limestone there 
is a small trap dyke, and there the limestone is frequently green. 
When the surface has been exposed to the air for some time, this 
green changes to a beautiful blue, a circumstance not easily ac- 
counted for. The iron and limestone, as well as the main rock, is 
cut through by these dykes. In the limestone near the dykes there 
is a very splendent variety of green coccolite, together with im- 
perfect crystals of diopside. It contains also phosphate of lime^ 
garnet, idocrase, and another mineral which we suppose to be a 
a nondescript. 
The existence of the dykes throws some light on the origin of 
primitive rocks in general. On this subject we venture to make 
the following remarks. The principal rock at this place is granite, 
or perhaps some would prefer to call it sienite, as it consists of feld- 
spar and hornblende; though the latter is in a small proportion only. 
It will be admitted at once, that these dykes are more recent than 
the rocks they traverse. Now when we attempt to account for 
their formation, and settle the questions how they came here, and 
what was their spurce, we readily perceive that it is more rational 
and more agreeable to established facts, to conclude that they must 
have been injected into cracks or fissures in the rocks while in a 
melted state, than to suppose them to have been formed by the fil- 
tration of matter from above while in solution in water; besides, 
.they exhibit marks of fusion themselves, and have also left the 
same on the rocks in which they are in contact. If it is onee ad- 
mitted that these dykes have ever been in a state of igneous fusion, 
then there must have'been a source of heat just beneath, sufficient 
to effect this fusion, for these dykes came from beneath the gra- 
nite. This admitted, and it is but a step farther to admit that the 
main rock containing the dykes was once in a slate of igneous fu- 
