388 THE DEPTHS OF THE SEA. (CHAP. VIII. 
has sufficiently proved that the low temperature is 
due to a branch of the Labrador current creeping 
down along the coast in a direction opposite to that 
of the Gulf-stream.. In the Strait of Florida this 
cold stream divides—one portion of if passing under 
the hot Gulf-stream water into the Gulf of Mexico, 
while the remainder courses round the western end 
of Cuba. 240 miles from the shore the whole mass 
of water takes a sudden rise of about 10° C. within 
25 miles, a rise affecting nearly equally the water at 
all depths, and thus producing the singular pheno- 
menon of two masses of water in contact—one 
passing slowly southwards, and the other more 
rapidly northwards, at widely different temperatures 
at the same levels. This abutting of the side of the 
cold current against that of the Gulf-stream is so 
abrupt that it has been aptly called by Lieutenant 
George M. Bache the ‘ Cold wall.’ Passing the cold 
wall we reach the Gulf-stream, presenting all its 
special characters of colour and transparency and of 
temperature. In the section which we have chosen 
as an example, upwards of three hundred miles in 
length, the surface temperature is about 26°5 C., 
but the heat is not uniform across the stream, for 
we find that throughout its entire length, as far 
south as the Cape Canaveral section, the stream is 
broken up into longitudinal alternating bands of 
warmer and cooler water. Off Sandy Hook, beyond 
the cold wall, the stream rises to a maximum of 
97°8 C., and this warm band extends for about 60 
miles. The temperature then falls to a minimum of 
26°°5 C., which it retains for about 30 miles, when a 
second maximum of 27°-4.C. succeeds, which includes 
