of the Gulf-stream. 485 
on approaching Havannah, on the morning of the 18th, we 
were apprised, by the colder temperature of 80°5, that during 
the preceding night we had entered the current, which de- 
scends from the northern shores of the Gulf of Mexico along 
the coast of Florida; and forms the head of the eulf-stream, 
In the subsequent passage from Havannah to the Straits of 
Bahama, on the 27th, 28th, and 29th of November, we crossed 
the narrow sea formed by the northern shore of Cuba and 
the Florida reefs, in which the waters of the stream are com- 
prised, previously to their discharge into the Atlantic: the 
surface-water in this passage varied from 80°*5 to 80°°7, which 
may therefore be considered as the initial temperature of the 
gulf-stream towards the end of November. The strait be- 
tween the Bahamas and the eastern side of Florida, which 
forms the outlet of the stream, is rather less than 200 miles 
in length, and from 33 miles at the narrowest part of the 
water-way, to 50 miles at the widest, in breadth. The Phea- 
sant was at the southern extremity of the strait at noon on the 
29th, and at the northern extremity at noon on the 30th, with 
The light rain which fell on the afternoon of the 14th of November, in 
the passage between Jamaica and Havannah, was a precipitation from an 
height above the earth’s surface, as the air near the surface was very far 
from being replete with moisture at the time. It was produced by the 
commencement of a wind from the N.E. (the same, I believe, which is 
called at Havannah, e/ Norte), which almost instantly lowered the tem- 
perature of the air two degrees at the surface, and of course correspondingly 
in its ascending progression, whilst the dew-point and its progression re- 
mained unaltered. ‘The height, therefore, at which the temperatures of the 
air and vapour would coincide by reason of the difference in their respec- 
tive ratios of cooling, would at once descend a space equivalent to that 
required to diminish the temperature of the air two degrees in its ascending 
progression, and a precipitation would take place throughout that space too 
copious to be altogether re-dissolved by falling into a warmer atmosphere ; 
and thus some portion of it would reach the surface, forming the light rain 
which we experienced, It was not, however, of long continuance, the su- 
perfluous moisture being disposed of, and the atmosphere speedily adapting 
itself to the new order of circumstances, by the processes which have been 
so well pointed out by Mr. Daniell, in his essay on the habitudes of an at- 
mosphere of permanently elastic fluid mixed with aqueous vapour. 
I am not able to assign with confidence the cause of the surface-water 
being only 80° on the morning of the 15th; but I suspect that it evidenced 
the presence of a thread of the current which descends from the northern 
shores of the Gulf of Mexico along the coast of Florida; and of which 
a small portion from the western border is sometimes turned to the west- 
ward by the northern coast of Cuba on which it impinges, and takes a 
course towards Cape St. Antonio. The charge of & convoy in a sea so 
much infested with pirates, was incompatible with the measures which 
would have been necessary to hive ascertained, more particularly, the cause 
of the decrease in temperature of the surface-water. 
$12 good 
