Of preparing and applying Objects. 59 
But, if we view a Fluid to find what ■„ 
Salts it may have in it, a Method quite con¬ 
trary -to the foregoing muft be employed : 
for then the Fluid muft be buffered to eva¬ 
porate, that the Salts, being left behind upon 
the Glafs, may more eafily be examined. 
Another, and indeed the mod: curious 
Way of examining Fluids, is, by applying 
them to the Microfcope in exceedingly fmall 
capillary Tubes, made of the thinnefl Glafs 
pofiible. This was Mr. Leeuwenhoek’s 
Method for difcovering the Shapes of Salts 
floating in Vinegar, Wine, and feveral other 
Liquors ; and fuch Tubes ihould be always 
ready to ufe as Occafion requires. 
For the Circulation of the Blood, Frogs, 
Newts, or Fifhes, are commonly made ufe 
of: and there are Glafs Tubes in the Single 
Microfcope, and a Fifli-pan, as well as Tubes, 
in the Double one, on purpofe to confine 
thefe Creatures, and bring the proper Parts 
of them to View : which, in Newts and 
Fifhes, are the Tails, and in Frogs the fine 
filmy Membrane between the Toes of the 
hinder Legs. Though, if we can contrive 
to fallen down the Creature, and bring our 
Objedfc to the Magnifier, the Circulation can¬ 
not pofiibly be feen fo plainly any where as 
in the Mefentery, or thin tranfparent Mem¬ 
brane that joins the Guts together ; and this 
Part, by pulling out the Gut a little, may 
•eafily be adj lifted to the Magnifier. 
To 
