[ 44-6 3 
See.) ; but finding they did not anfwer my purpofe, 1 
tried frefh-water alone, which I expofed to the open 
air for two days, and upon examining found a good 
number of animalcula ; but they foon languifhed and 
died. I afterwards expofed the frefh water for two 
hours only, and found fome in it, which lived but a 
very fhort time. I therefore refolved to try fea-water, 
which, having been expofed to the open air, in a 
very fhort time, fwarmed with animalcula ; thefe, 
upon the ftridteft examination, I found to be exactly 
of the fame fpecies with thofe of frefh water : only 
they feemed much more adtive and lively, and in- 
head of dying in a fhort time, as thofe of the frefh 
water, they continued to increafe and thrive wonder- 
fully, the longer I kept them. I then removed fome of 
them out of the fait into the frefh water ; but they 
foon languifhed and died. Whence I conclude them 
to be a quite different fpecies from what we find 
upon, or near, the land. I began my experiments 
about ten days after we loft fight of land, and con- 
tinued them the whole voyage; fo that, with the 
help of fome books, I pafied my time very agree- 
ably. 
I had provided myfelf with a thermometer, to 
meafure the degrees of heat and cold, in the dif- 
ferent climates we were to pafs through; and found 
the mercury to rife from ^ to 8o° of Fahrenheit’s 
fcale : which laft it never exceeded, though we were 
fometimes becalmed between the tropics, and upon 
the line. This degree of heat I have often ex- 
perienced in Canada, as I dare fay you fometimes 
have in England. 
J 
When 
