Infects on the Bark of the Aft. 373 
Anditis worthremarking 3 that every fingle 
Infedt, befides being inclofed in this Covering 
of Silk, which is common to 30 or 40 of 
them, has a pure white tranfparent Cafe or 
Shell, which being left by the Infedt nearly 
refembles the Shape of an Hen’s Egg; and if 
they are not difturbed at the Time of hatch¬ 
ing, mod: of their Egg-fhells will be found 
empty under the common Coverture,. And by 
attending to them a little, one dial] fee,'at the 
fame Time, feveral of thefe Infedts hatched, 
fome juft breaking out of their Shells, and 
others creeping about with their Shells hang¬ 
ing to their Tails, as at N° xm. 
My Friend’s Account fays, that the larged: 
of thefe Animalcules meafured little more 
than the 114th Part of an Inch in Length, 
and the 200th Part of an Inch in Breadth; 
and confequently the Number of them re¬ 
quired to cover a fuperficial Square Inch 
would be fomething more than 22800 ** 
His Method of finding their Magnitude 
was as follows.—In order (fays he) to be 
certain of the magnifying Power of the Glafs 
I made ufe of, (which was the third Magni¬ 
fier) I divided a Line, drawn exactly an Inch 
in Length on a Slip of round Glafs, into 20 
equal Parts. Then placing this Slip of Glafs 
under the Microfcope, I threw the magni- 
hed Image of one of thefe 20th Parts upon 
* This is the leaf! Infe£t I have obferved produced out 
W the Water. 
B b 3 a. Scale 
