POWERS OE -GLASSES. 
325 
said distance is. When that is known, compute how many times those 
parts of an inch are contained in eight inches, the common standard 
of sight, and that will give you the numbers of times tire diameter is 
magnified : squaring the diameter will give you the superficies; and if 
it be an object whose depth or whole contents you would learn, mul- 
tiplying the superficies by the diameter will show the cube or bulk. 
A Table of the magnifying Powers pf Convex Glasses employed in 
Single Microscopes, according to the Distance of their focus; cal- 
culated by the Scale of an Inch divided into a Hundred Parts: 
showing how many Times the Diameter, the Superficies, or the 
Cube of an Object is magnified, when viewed through such Glasses, 
to an Eye vvhose natural Sight is at Eight Inches, or Eight Hundreds 
of a Hundredth Part of an Inch. 
Focal Distance of 
the Lens or Micro- 
scope in lOOdths of 
an Inch. 
Number of Times 
that the Diameter 
of anObject is mag- 
nified. 
Number of Times 
that the Surface of 
an Object is mag- 
nified. 
Number of Times 
that the Cube of an 
Object is magnifi- 
ed. 
■J or 50 
16 
256 
4,096 
-As « r 40 
20 
400 
8,000 
y'g or 30 
26 
676 
17,576 
-I or 20 
40 
1,600 
64,000 
15 
53 
2,806 
148,877 
14 
57 
3,249 
185,193 
13 
61 
3,721 
226,981 
12 
66 
4,356 
287,496 
11 
72 
5,184 
373,248 
-h Of 
80 
6,400 
512,000 
9 
88 
7,744 
681,472 
8 
100 
10,000 
i,ooo,ooq 
7 
114 
12,996 
1,481,544 
0 
133 
17,689 
2,352,637 
WW or 5 
160 
25,600 
4,096,000 
4 
200 
40,000 
8,000,000 
3 
266 
70,756 
18,821,096 
-Ar or 2 
400 
160,000 
64,000,000 
1 
800 
640,000 
512,000,000 
