[12] The Gulf-stream at the narrowest place examined by the Coast Survey, and where also its velocity was greatest, was found to be over 30 statute miles broad and 1,950 feet deep. But we must not suppose that this represents all the warm water which is received by the Atlantic from the equator; a great mass flows into the Atlantic without passing through the Straits of Florida.
[13] It is probable that a large proportion of the water constituting the south-eastern branch of the Gulf-stream is never cooled down to 40°; but, on the other hand, the north-eastern branch, which passes into the arctic regions, will be cooled far below 40°, probably below 30°. Hence I cannot be over-estimating the extent to which the water of the Gulf-stream is cooled down in fixing upon 40° as the average minimum temperature.
[14] “Physical Geography of the Sea,” § 24, 6th edition.
[15] “Physical Geography,” § 54.
[16] Trans. of Roy. Soc. of Edin., vol. xxi., p. 57. Phil. Mag., § 4, vol. ix., p. 36.
[17] “Smithsonian Contributions to Knowledge,” vol. ix.
[18] “Heat as a Mode of Motion,” art. 240.
[19] Trans. Roy. Soc. of Edin., vol. xxv., part 2.
[20] See “Smithsonian Contributions to Knowledge,” vol. ix.
[21] “Meteorology,” section 36.