4 
The rear trunnions are made hollow for the admission through them of the 
charge of compressed air. The latter is enclosed in 32 reservoirs arranged in 
four rows of eight, two rows on each side of the carriage. These reservoirs are 
four feet long, 10 inches in diameter, and ‘75 inch in thickness. They are 
proved at a pressure of four tons per square inch, and the air in them exerts 
a pressure of about two and a quarter tons per square inch, a pressure at which 
each reservoir contains five and a half tons of air with a volume of 629 cubic 
yards at atmospheric pressure. 
Any number of reservoirs may be discharged simultaneously according to the 
weight of the projectile and the range. 
An automatic lubricator is fitted at the side of the firing valve whereby oil 
escapes into the bore and is distributed throughout its length by the compressed 
air. 
The carriage is formed of thick steel brackets, upon which are riveted massive 
cast-iron supports for the trunnions. It stands with the aid of conical rollers on 
a circular cast-iron bed, seven yards in diameter, formed of segments built into 
the platform, and is moved by a compressed air machine (Heenan and Froude’s) 
on a complete circle, so that it can be fired in any direction. 
The service of the gun, laying, loading, and firing, is performed by a single 
man using in succession various levers. It is expected that a rate of fire of one 
round a minute will be attained. The reservoirs are filled by a special compres¬ 
sion machine, a modification of those made by Mr. H. Lane for the compression 
of oxygen, hydrogen, and carbonic acid. The air in it is compressed in four 
successive periods, to each of which corresponds a piston of successively decreas¬ 
ing diameter : the first piston, which draws its supply from the atmosphere, has 
a diameter of 12 inches; the last, which forces its supply into the reservoir, has 
one of only two and a quarter inches. After each compression the air is cooled 
by a circulating serpentine of water. 
In addition to the foregoing gun Mr. Gray don proposes the following pieces :— 
Length 
O) 
’1 So 
Number. 
Type. 
Calibre. 
(approxi¬ 
Carriage. 
Remarks. 
mate.) 
p ° 
inches. 
feet. 
lbs. 
■! 
For gunboat of the Am¬ 
men model and for per¬ 
manent works. 
} 21 
40 
1200 | 
Turret pattern with 
central pivot. 
2 1 
q 17 
37 
9ooq 
1 
3 y 
Ships and permanent 
works. 
1 
y i5 
34 
1 
600 y 
Fixed pivot. 
4 J 
J 13 
31 
400 J 
:} 
Ships, siege and permanent 
works. 
51 
22 
16 
120-J 
60 j 
Fixed pivot and 
siege. 
| Revolver. 
7 
Boats and field. 
3 
14 
•i 
Fixed pivot and 
field. 
| Revolver. 
The gunboat, for which No. 1 model has been designed, is due to Admiral 
Ammen of the United States Navy. She is expected to have a speed of 20 
knots. She will carry four dynamite projectors in two turrets, one forward and 
one aft. The siege piece of nine inches will fire a round in two minutes at a 
range of 5000 yards. 
The revolver pieces have five tubes and can fire 75 rounds a minute. 
