CHAP. V.] THE GULF-STREAM. 363 
west prevented our dredging. At about 1 a.m. there was a 
sudden rise of the thermometer at the sea surface from 12°-2 ©. 
to 18°-2 C., and it rose steadily during the next eight hours up 
to 22° C., showing that we had entered the Gulf-stream current. 
The passage from the dull-green color of the arctic reflux to the 
deep blue of the Gulf-stream was very perceptible on this ocea- 
sion. We continued in the Gulf-stream until shortly after mid- 
night on the 25th, when a sudden change in the temperature of 
the surface of the sea from 22°-2 C. to 18° C. showed that we 
had crossed its southern limit. In crossing the Gulf-stream in 
both directions, the alternate bands or interdigitations of warm 
and cold water were very perceptible. Half-hourly temperature 
observations were taken (Appendix D), and the diagram Plate 
XII. is constructed from the general results. 
In a former volume (“The Depths of the Sea,” Chapter 
VIII.), I have given a general account of the Gulf-stream, and 
I have entered somewhat fully into the recent controversies re- 
garding its origin and influence. Since that book was written, 
greater harmony of opinion appears to obtain on these points. 
It seems to be generally admitted that the Gulf-stream is due 
to the reflux of the equatorial current, and that it is not in any 
sense a modified case of a general ocean circulation produced 
by convection; and most physical geographers seem to be at 
one as to the very important influence which it exerts in dis- 
tributing and accumulating tropical warmth in the North At- 
lantic, and in ameliorating the climatic conditions of the coun- 
tries which border its eastern shores. We have since had an 
opportunity of tracing the distribution of temperature in the 
corresponding region of the North Pacific, and the comparison 
between the two is very instructive. The differences between 
them are great, but when carefully considered they are found 
to be more differences in degree than in kind. 
In the Pacitic the ocean area is of course vastly greater than 
in the Atlantic, and the equatorial current is to the full as 
