um of the Ordnance Yard at
Washington.

130. The size of the grains is determined by sieves, made by piercing
round holes in thin plates of brass. These sieves are five in number,
the holes being of the following diameters, viz.:

No. 1, .3 of an inch } Initial Velocity required,
No. 2, .15 do. } 1450 feet + 50 - 50, for Rifle.

No. 2, .15 do. } Initial Velocity required,
No. 3, .10 do. } 1500 feet + 50 - 50, for Cannon.

No. 4, .06 do. } Initial Velocity required,
No. 5, .02 do. } 1550 feet + 50 - 50, for Musket.

Rifle powder is used in the Parrott rifles of 8-inch, 100-pounder, and
60-pounder. Navy cannon powder in all other rifles and all
smooth-bores.

131. Size of the grain is required to conform to the following:

Pass through No. 1 }
Remain on No. 2 } all Rifle.
Pass through No. 2 }
Remain on No. 3 } all Cannon.
Pass through No. 4 }
Remain on No. 5 } all Musket.

Ten per cent. variation tolerated.

132. GRAVIMETRIC DENSITY, is the weight of a given measured quantity:
it is usually expressed by the weight of a cubic foot in ounces.

This cannot be relied on for the true density, as the size and shape
of the grain may make the denser powder seem the lighter.

Cannon powder should have a gravimetric density of about 875 oz., and
not exceeding 900 oz., to the cubic foot. (It actually varies with
different makers from 875 to 975.)

133. SPECIFIC GRAVITY.--The specific gravity of gunpowder is between
1.70 and 1.75.

All the powder of any lot being made of the same mill-cake, the
specific gravities are equal although the gravimetric densities may
vary.

134. Powder for small arms, or musket powder, should all pass through
No. 4, none through No. 5, and average from 2,000 to 2,500 kernels in
tea grains Troy.

All powder should be well glazed; for small arms more highly than for
cannon.

135. The system of granulation adopted by the Army differs from that
of the Navy, as follows:

ALL THROUGH-- ALL ON--
Mammoth 0.9 in. 0.6 in.
Cannon 0.35 0.25
Mortar 0.10 0.06
Musket 0.06 0.03

It will be seen by this Table that under the Army nomenclature, Navy
Rifle nearly corresponds to Army Cannon; that the Army Mortar is the
nearest equivalent to Navy Cannon, but with much more fine g