The Magnifying Power of Glaffes . 3 f 
be pleafed to know certainly what the Pow¬ 
ers of their Glaffes are, and confequently 
what may be expected from them, it would 
be much better if the Microfcope-Makers 
would grind their Glaffes according to fome 
fettled Standard, and not work by Guefs, as 
they ufually do at prefent, whereby no two 
Sets of Magnifiers can be fuppofed exactly 
alike. Such a Standard, which would afford 
a very ufeful Set of Glaffes, magnifying one 
more than another in due Degrees, is, X 
think, as follows. 
The FOCAL DISTANCES of 
Six Magnifiers for Mr. Wilson’s 
Pocket Microfcope. 
g 
sT 
1. 
2 . 
3 * 
4? 
5 * 
6 , 
Dift. of 
Ythe Fo-^ 
cus at 
tV» or , 
tb > or 5 
8 
16 
O 
To) or 30 
1 
V. z* 
or 50 
Magnifies the 
Diam. 
400 
160 
100 
5 ° 
—26 
-16. 
t ^ 
> a 
• rn 
h 
Magnifies the 
Superficies 
i6o,ooo"| 
-25,600 | 
10,000 f 
1 2,500 j F 4 
— 676 
— 256^ 
D 4 
