ing of this _French_ Book but one Copy, that is known, in
_England_.

A _TABLE_ of the _Apertures_ of _Object-Glasses_.

_The Points put to some of these Numbers denote Fractions._

Lengths of |For excellent| For good |For ordinary |
Glasses. | ones. | ones. | ones. |
Feet, Inches.|Inch, Lines.|Inch, Lines.|Inch, Lines.|
| | | |
4| 4.| 4| 3|
6| 5.| 5| 4|
9| 7| 6| 5|
1 0| 8.| 7| 6|
-------------|-------------|-------------|-------------|
1 6| 9| 8.| 7|
2 0| 11| 10| 8|
2 6|1 0| 11| 9|
3 0|1 1|1 0| 10|
-------------|-------------|-------------|-------------|
3 6|1 2.|1 1| 11|
4 0|1 4|1 2|1 0|
4 6|1 5|1 3|1 .|
5 0|1 6|1 4|1 1.|
-------------|-------------|-------------|-------------|
6 |1 7.|1 5|1 2|
7 |1 9|1 6|1 3|
8 |1 10|1 8|1 4|
9 |1 11.|1 9|1 5|
-------------|-------------|-------------|-------------|
10 |2 1|1 10|1 6|
12 |2 4|2 0|1 8|
14 |2 6|2 2|1 9.|
16 |2 8|2 4|1 11.|
18 |2 10|2 6|2 1|
20 |3 0|2 7|2 2.|
-------------|-------------|-------------|-------------|
25 |3 4|2 10|2 4.|
30 |3 8|3 2|2 7|
35 |4 0|3 4.|2 10|
40 |4 3|3 7|3 .|
-------------|-------------|-------------|-------------|
45 |4 6|3 10|3 2.|
50 |4 9|4 0|3 4.|
55 |5 0|4