the Eeaiier^ that he hath found, that the Apertuns^ which Opticl^ 
G/^^v can bear with diftincftiiefs , are in about a fubduplicate 
proportion to their Lengths 5 whereof he tells us he intends to give 
the reafou and demonftration inhis Of^/^^/^r,^/, which he is now 
writing, and intends to finifli, as foon as his Health will permit. 
In the mean time, he prefents the 'Reader with a Table of fuch 
Jpertures ; which is here exhibited to the Confideration of the 
Ingenious, there being of this French Book but one Copy, that 
is knowU; in England, 
A T ABLE oiiht Apertures of ObjeB- GlaJJeS. 
The points put to fome cf thefe NnrKbers denote Fr anions* 
1 Lengths of 
Glafses. 
Feet, Inches. 
4 
6 
9 
o 
For excellent For good 
07ies. 1 ones. 
Inch. Lines. Inch. Lines 
9 
1 1 
o 
I 
8. 
10 
1 1 
o 
O I 
2. 
4 
S 
6 
I 7 
I 9 
I 10 
I II. 
10 
12 
14 
i6 
18 
20 
42 
6 
8 
10 
02 
S 
6 
8 
9 
10 
c 
2 
For ordinary Lengths of 
ones. Glafses. 
Inch. Lines Feet. Inches. 
7 
8 
9 
10 
II 
o 
4|i 
612 
7I2 
6 
8 
9. 
I 
2, 
25 
35- 
40 
45- 
50 
55 
60 
6s 
70 
75 
80 
90 
ICQ 
120 
IfO 
200 
250 
300 
350 
400 
For excellent For gosd \For ordiaary 
ones. I ones. ones. 
Inch. Lines. Inch* Lines. \lnch. Lines. 
4j^ 
03 
3? 
102 
2 ^ 
2 
3 
^3 
94 
04 
44 
74 
95 
II 
9 
1© ^ 
11 <5 
12 6. 
13 4 
10 
o 
4- 
7 
10 
33 
83 
10 4 
o4 
2'4 
2. 
4. 
S. 
10 
4r 
8 
07 
(J ,4 
94 
^5 
o5 
68 
7. 
10 
3 
II 
9 
lO 
n 
© d 
0,8 
9,9 
6:9 
9 
8. 
5 
o 
8 
