the Water in the Gulf-Jiream. 
for the number of miles that the (hip is fet to the northward, 
by multiplying the time into the velocity of the current. 
Though this velocity is hitherto very imperfectly known, for 
want of fome method of determining how long the current 
acted upon the drips, yet all uncertainty ariiing from thence 
mu if foon ceafe, as a few experiments upon the heat of the 
ftream, compared with the (hip’s run checked by observations 
of the latitude, will afcertain its motion with fufficient preci- 
flon. From differences in the wind, and perhaps other cir- 
cumftances, it is probable, that there may be fome variations 
in the velocity of the current; and it will be curious to ob~ 
ferve, whether thefe variations may not frequently be pointed 
out by a difference in its temperature ; as the quicker the cur- 
rent moves, the lefs heat is likely to' be loft, and confequently 
the hotter will the water be. In this obfervation, however, the 
feafon of the year muft always be con fide re d ; partly, becaufe 
it may, perhaps, in fome degree affedl the original temperature 
of the water in the gulf of Mexico ; but principally, becaufe 
the aftual heat of the ftream muft be greater or lefs in propor- 
tion as the trad of the fea through which it has flown was 
warmer or colder. In winter, I Ihould ftippofe, that the heat 
of the ftream itfelf would be rather lefs than in fummer ; but 
that the difference between it and the furround’mg fea would be 
much greater ; and I can conceive that, in the middle of fum- 
mer, though the ftream had loft very little of its original heat, 
yet the fea might, in fome parts, acquire fo nearly the fame- 
temperature, as to render it fea reefy pofiible to diftinguifh by 
the thermometer when a fhip entered into the current. 
Befides the convenience of correcting a {hip’s courfe, by 
knowing how to make a proper allowance for the diftance (he is 
let to the northward by the current, a method of determining 
Z z 2 with 
