320 Lieut.-Col. Sabine on the Cause of Mild Winters 



" One previous and similar instance is on record, in which 

 the water of the Gulf-stream was traced by its temperature 

 quite across the Atlantic to the coast of Europe ; this was by 

 Dr. Franklin, in a passage from the United States to France, 

 in November ] 776*. The latter part of his voyage, i. e. from 

 the meridian of 35° to the Bay of Biscay, was performed, with 

 little deviation, in the latitude of 45°; in this run exceeding 

 1200 miles, in a parallel of which the usual temperature, to- 

 wards the close of November, is about 55^°, he found 63° in 

 the longitude of 35° W., diminishing to 60° in the Bay of 

 Biscay; and 61° in 10° west longitude, near the same spot 

 where the Iphigenia found 5 5 °* 7 on the 6th of January, being 

 about five weeks later in the season. At this spot then, where 

 the Iphigenia crossed Dr. Franklin's track, the temperature 

 in November 1776 was 5^°, and in January 1822, 3 0, 2 above 

 the ordinary temperature of the season. 



"There can be little hesitation in attributing the unusual 

 extension of the stream in particular years to its greater ini- 

 tial velocity, occasioned by a more than ordinary difference in 

 the levels of the Gulf of Mexico and of the Atlantic; it has 

 been computed by Major Rennell, from the known velocity of 

 the stream at various points of its course, that in the summer 

 months, when its rapidity is greatest, the water requires 

 about eleven weeks to run from the outlet of the Gulf of 

 Mexico to the Azores, being about 3000 geographical miles ; 

 and he has further supposed, in the case of the water of which 

 the temperature was examined by Dr. Franklin, that perhaps 

 not less than three months were occupied, in addition, by its 

 passage to the coasts of Europe, being altogether a course ex- 

 ceeding 4000 geographical miles. On this supposition, the 

 water of the latter end of November 1776 may have quitted 

 the Gulf of Mexico, with a temperature of 83°, in June ; and 

 that of January 1822, towards the end of July, with nearly 

 the same temperature. The summer months, particularly 

 July and August, are those of the greatest initial velocity of 

 the stream, because it is the period when the level of the Ca- 

 ribbean Sea and Gulf of Mexico is most deranged. 



" It is not difficult to imagine that the space between the 

 Azores and the coasts of the old continent, being traversed 

 by the stream, slowly as it must be, at a much colder season 

 in the instance observed by the Iphigenia than in that by Dr. 

 Franklin, its temperature may have been cooled thereby to a 

 nearer approximation to the natural temperature of the ocean 

 in the former than in the latter case ; and that the difference 



* Franklin's Works, 8vo, London, 1806, vol. ii. pp. 200, 201. 



