286 ' THE ATLANTIC. [ouap. rv. 
fathoms at a distance of seven miles; and to the southward of 
2250 fathoms at ten miles. The only direction in which there 
would seem to be a series of banks is along an extension of 
the axis of the reef to the south-west. We anchored for a 
night in 30 fathoms water on this line about twenty miles 
from the edge of the reef, and a shoal is mentioned at a still 
greater distance in the same direction. About three hundred 
miles farther on, however, a sounding is given of 2950 fathoms, 
and there seems little probability that there is any connection 
between the Bermudas reef and the Bahamas. What the basis 
on which the Bermudas reef rests may be, we have no means 
of telling; in fact, its having the form of an atoll precludes 
the possibility of our doing so. There seems to be little doubt, 
from Darwin’s beautiful generalization, which has been fully 
indorsed by Dana and other competent observers, that the atoll 
form is due to the entire disappearance by subsidence of the 
island round which the reef was originally formed. The ab- 
ruptness and isolation of this peak, which runs up a solitary 
cone to a height about equal to that of Mont Blanc, are cer- 
tainly unusual; probably the most reasonable hypothesis may 
be that the kernel is a volcanic mountain comparable in char- 
acter with Pico in the Acores or the Peak of Teneriffe. 
There is only one kind of rock in Bermudas. The islands 
consist from end to end of a white granular limestone, here 
and there becoming gray or slightly pink, usually soft, and in 
some places quite friable, so that it can be broken down with 
the ferrule of an umbrella; but in some places, as on the shore 
at Hungry Bay, at Painter’s Vale, and along the ridge between 
Harrington Sound and Castle Harbor, very hard and compact, 
almost erystalline, and capable of taking a fair polish. This 
hard limestone is called on the islands the “ base rock,” and is 
supposed to be older than the softer varieties, and to lie un- 
der them, which is certainly not always the case. It makes 
an excellent building stone, and is quarried in various places 
