[ 5°5 3 
all pofllblc Advantage of the Light. The Lens 
being fet fo as to be brought dofe to the Eye, is alfo 
of great Ufe, lince thereby a larger Part of the Ob- 
ject may be feen at one View. 
It muft be remembered, that all thefe Microfcopes 
are of one and the fame Structure, and that the moft 
fimple poflible, being only a fingle Lens, with a 
moveable Pin before it, on which to fix the Objed, 
and bring it to the Eye at Pleafure. 
Though I was fenfible it muft coft much Trouble 
to meafure the focal Diftances of thefe 2 6 Micro- 
fcopes, and thereby afcertain their Powers of mag- 
nifying, I confidered that, without fo doing, it would 
be impoflible to form a right Judgment of them, or 
make any reafonable Comparifon between them and 
our own. This Task therefore I have performed, 
with as much Care and Exadnefs as I was able ; and 
have (hewn, in the following Table, how many of 
them have the fame Focus, and confequently mag- 
nify in the fame Degree? how many times they 
magnify the Diameter, and how many times the 
Superficies of any Objeds applied to them. I have 
given the Calculations in round Numbers, the Frac- 
tions making but an inconfiderable Difference ; and 
hope any Miftakes I may have made in fo nice a 
Matter will be excufed. 
.OObl * * • * • 
Ttt 
A 
