520 APPENDIX. 
ocean to the east of it; while the still greater cold of the sea-water 
on its western side, between the Gulf Stream and the continental 
shore, is explained hy the great Arctic current, pouring down from 
Baffin's Bay, and skirting the shore of North America as far as the 
Coast of Florida, until it is lost in that latitude under the Gulf 
Stream. The object of Dr. Bache's investigation was to trace the 
mutual relations of these two great currents of warm and cold 
water, flowing side by side in opposite directions, and to discover 
the conditions which regulate their movements and keep them 
within definite limits. 
The investigation is even now by no means complete, though it has 
been going on for many years. It has, however, been ascertained 
that, while the ocean-bed deepens more or less rapidly as we recede 
from the shore, forming a trough in which the Gulf Stream flows, 
this trough is limited on its eastern side by a range of hills trend- 
ing in the direction of the current, outside of which is another de- 
pression or valley. Indeed, the sea-bottom exhibits parallel ridges 
and depressions, running like the shore of the continent itself,.in a 
northeasterly direction. The water presents differences of tem- 
perature, not only on the surface, but at various depths below. 
These inequalities have been determined by a succession of 
thermometric observations along several lines, crossing the Gulf 
Stream from the shore to the ocean water on its eastern side, at 
intervals of about a hundred miles. The observations have been 
made first at the surface, and then at successively greater depths, 
varying from ten to twenty, thirty, one hundred, two hundred, and 
even three and four hundred fathoms. This survey has shown 
that, while the Gulf Stream has a temperature higher than that 
of the waters on either side, it is also alternately warmer and 
colder within itself, being made up as it were of distinct streaks 
of water of different temperature. These alternations continue to 
as great a depth as the observations have been carried, and are 
found to extend even to the very bottom of the sea, where this has 
been reached. The most surprising part of this result is the 
