Structure and 0 economy of Whales. 39 - 
The fpermaceti does not become rancid, or putrid, nearly fo 
foon as the other animal oils ; which is moft probably owing to 
the fpermaceti being for the mod: part in a folid date ; and I 
fhould fuppofe, that few oils would become fo foon rancid as 
they do, if they were always preferved in that degree of cold 
which rendered them folid : neither does this oil become fo foon 
putrid as the flefh of the animal ; and therefore, although the 
oil in the cells appeared to be putrid before boiling, it was 
l'weet when deprived of the cellular fubdance. The fperma- 
ceti is rather heavier than the other oil. 
In this animal then we find two forts of oil, beddes the 
deeper feated fat, common to all of this clafs ; one of which erv- 
dallifes with a much lefs degree of cold than the other, and of 
courfe requires a greater degree of heat to melt it, and forms, 
perhaps, the larged crydals of any expreded oil we know : 
yet the fluid oil of this animal will crydallife in an ex- 
treme hard frod, much fooner than mod edential oils, though 
not fo foon as the expreded oils of vegetables. Camphire, how- 
ever, is an exception, fince it crydallifes in our warmed wea- 
ther, and when melted with expreded oil of vegetables, if 
the oil is too much fnturated for that particular degree of cold, 
crydallifes exactly like fpermaceti. 
In the Ox the tallow, and what is called Neat’s-foot oil, cry- 
dallife in different degrees of cold. The tallow congeals with 
rather lefs cold than the fpermaceti; but the other oil is fimilar 
to what is called the train oil in the Whale. 
I have endeavoured to difeover the form of the crydals of 
diderent forts of oil ; but could never determine exa&ly what 
that was, becaufe I could never find any of the crydals lingle, 
and bv bein^ always united, the natural form was not didinct. 
1 Kkk 2 ft 
