140 Mineralogy and Geology of a part of Nova Scotia. 
inperfectly polished fragments among the rolled masses on 
the shore. A vein of magnetic oxide of iron about a foot 
wide was also observed entering the superincumbent trap. 
But the substance for which this island has long been 
known by the inhabitants of the country is amethyst ; which, 
occurring plentifully in crystals of fascinating beauty, draws 
hither the passing traveller, who seldom departs without 
something ornamental to his parlor shelf, or useful to science. 
- Pursuing the northern shore of the Basin of Mines, east- 
wardly, the next place deserving of notice is the vicinity of 
the Two Islands, about six miles from Partridge Island. The 
intermediate cuast, being composed of rocks of a different 
character from those which it is our object at present to de- 
scribe, we shall leave, to notice it more particularly when we 
treat of that formation. .— 
The Two Islands consist of amygdaloid and columnar 
reenstone rising on all sides abruptly from the sea, and be- 
ing accessible at their bases only at low water will not afford 
the visitor many interesting specimens. On the main land 
near Swan’s Creek, and opposite to these islands, he will be 
favored with a locality of uncommon interest. At this place 
also we have a second, and perhaps better developed exam- 
ple of the conversion of shale, red sandstone, and compact 
trap, first into a coarse breccia, consisting of loosely united 
masses of these rocks, then into a more compact breccia, 
consisting of similar masses more closely united, though 
distinguishable from each other, and finally, by consecu- 
tive gradations, into a genuine, well characterized amy 
daloid, in which the most critical eye would fail to distingui 
separately its component ingredients, We have in our pos- 
session specimens from this place, which illustrate perfectly 
the changes of which we speak, and which present these 
three rocks tending to the production of amygdaloid. The 
color of this amygdaloid is obviously governed by the rela- 
tive quantity of the ingredients composing it; for if the sand- 
stone and red slate predominate, the color is then nearly of a 
brick red, as the appearance of the rock itself abundantly 
peoens but when it assumes a greenish or greyish black co- 
or, we infer that the slate and sandstone form a compara 
tavely small proportion of the mass. j 
~ Having thus adverted to the character of this rock in pat- 
fcular, we shall notice more generally the appearance of the 
. 
