‘Mineralogy and Geology of Nova Scotia. 241 
not confirmed by the precisely analogous phenomena presented 
by rocks of known igneous origin ; such, for example, as the vol- 
canic lavas and obsidians of Iceland and the Lipari Isles, cited 
by Mr. Scrope, in his able work on Volcanos.* 
The occurrence, too, of similar cavities in the secondary trap 
of other regions, has been mentioned by several writers on geol- 
ogy, and in this country especially by Professor Hitchcock, who, 
in his valuable notices of the trap bordering on the Connecticut 
River, aptly remarks, that the rocks in which they there occur, 
“appear as if bored through repeatedly by an auger.” + And 
in a paper which we have recently noticed in the “Trans- 
actions of the Royal Society of Edinburgh,” { written by Mr. 
Trevelyan, we find them mentioned as occurring in the trap of 
one of the Ferroe Islands. This careful observer ascribes 
their origin to the escape of an elastic fluid through the mass of 
this rock while soft. 
We shall take occasion hereafter to show the relations of shale, 
red sandstone, and trap, in the production of trap tuff and amygda- 
loid ; which will lead us to infer, that the vicinity of the trap is 
necessary to the formation of amygdaloid, and that the produc- 
tion of that rock was attended by heat. But before leaving this 
cove, we would mention, that foliated heulandite occurs in veins 
two or three inches wide in the amygdaloid, and that mesotype 
is found abundantly in the soil formed by the disintegration of 
this rock. 
From St. Croix Cove, pursuing the coast easterly, the amyg- 
daloid, crowned with columnar trap, continues and forms an ab- 
rupt precipice for about five miles, where it is again interrupted 
* Page 113. + Silliman’s Journal, Vol. VI. p. 52. ¢ Vol. IX. 
56 
