No.

Inch.

00

-

1/8

0

-

5/32

1

-

3/16

2

-

7/32

3

-

1/4

4

-

9/32

No.

Inch.

5

-

5/16

6

-

11/32

7

-

3/8

8

-

13/32

9

-

7/16

10

-

15/32

No.

Inch.

11

-

1/2

12

-

9/16

13

-

5/8

14

-

3/4

15

-

7/8

16

-

1

No.

Inch.

17

-

1 1/8

18

-

1 1/4

19

-

1 3/8

20

-

1 1/2

Messrs. John Bradley & Co.'s Nail Rod Gage

No.

Inch.

00

-

1/8

00 1/2

-

9/64

0

-

5/32

-

11/64

1

-

3/16

No.

Inch.

1 1/2

-

13/64

2

-

7/32

2 1/2

-

15/64

3

-

1/4

3 1/2

-

17/64

No.

Inch.

4

-

9/32

4 1/2

-

19/64

5

-

5/16

5 1/2

-

21/64

6

-

11/32

No.

Inch.

Inch.

7

-

3/8

8

-

13/32

9

-

7/16

10

-

15/32

11

-

1/2

It will be perceived that the intervals, from 00 1/2 to 3 1/2 are the 64th of an inch, from 4 to 11 the 32nd, and above 18, the differences are 1/8 of an inch. This mode, although systematic, is objectionable, as there is no evident relation between the numbers and their corresponding measures, and therefore both hare to be impressed upon the mind.

In guns of most kinds, the weight of the belle determine the denominations of their respective sixes. Thus it is well known that heavy guns or ordnance are named 6. 9. 12 to 68 pounders, from having bores respectively suited to iron shots of those reapective weights, the bore is always 1/50th larger in diameter than the shot, the difference being known as windage. The sizes of the bores of mortars and modern guns intended for hollow shot, are designated in inches, as 8,10, 13 inch mortars, &c

In rifles and fowling-pieces, the diameters of the bores, designated as No. 1. 2. 3. 4. 5. etc, are the diameters respectively of leaden bullets or spheres, of which 1. 2. 3. 4. 5. Ac weigh exactly one pound avoirdupoise; and as the subject may have an interest for some of the readers of this volume, the following particulars of the weights of the balls in grains, and of the diameters both of the balls and of the barrels in hundredths of an inch, are transcribed from Mr. Wilkinson's gage, which he has constructed with great care.