THE ROYAL ARTILLERY INSTITUTION. 
293 
On the upper side of the steady plug is cut an annular groove or recess 
into which is pressed detonating composition.* * * § 
To give the composition a more secure hold, the bottom of the annular 
recess is roughed by a number of small grooves formed in it. Over the top 
of the detonating composition is fixed a thin copperf washer sufficiently strong 
to prevent action taking place on the shell striking water with a high velocity, 
although not strong enough to interfere with the proper action of the fuze 
when the shell strikes a ship^s side or similar hard substance with a low 
velocity. Two conical fire holes pass vertically through the steady plug from 
the detonating composition. 
The other points in which the construction of this fuze differs conspicuously 
from that of the other Pettman fuzes, are:— 
(1) The cone plug, which is no longer coned at the top although it retains 
the name, has in addition to the central fire hole, two inclined fire holes 
passing into the tube. Its construction is otherwise the same as that of the 
sea service fuze. 
(2) The parts of the fuze are supported not by a lead cup but by a copper 
“ suspending wire.”J The support afforded by the wire is not ultimately 
greater than that which is afforded by the lead cup in the other fuzes, that 
is to say, no greater shock is required to shear it than is required to crush 
the lead cup, but the wire not being affected by the small shocks to which a 
fuze is subject in transport, is on the whole more reliable than a lead cup, 
which being neither rigid nor elastic, yields little by little to a succession of 
such small shocks, sufficiently in the end to deprive the parts of the fuze of 
the necessary support. The wire passes through the tube of the cone plug 
and rests upon the bottom of the fuze. No action can take place until the 
wire is broken. 
The lower part of the central hole of the tube is sufficiently enlarged to 
prevent it from being closed by the suspending wire; above the suspending 
wire the hole is contracted. 
(3) The support of the parts of the fuze being dependent upon the sus¬ 
pending wire, the lead cup which the fuze contains performs only the 
secondary functions of the same cup in the other fuzes, viz. it serves to rivet 
down the cone plug after discharge and prevents re-action. § 
(4) Externally the general service fuze is conical without any projecting 
shoulder. It is screwed to the general service fuze hole gauge [| all the way 
down. 
* The same detonating composition as is used for covering the detonating hall in the land and 
sea service fuzes, vide p. 77. The composition however is pressed dry into the plug. 
f The copper is , 008 // thick. 
$ The wire is •087" thick. 
§ The form and size of the cup are slightly different from those of the land and sea service cups. 
It weighs from 102 to 114 grs. The considerations as to the purity of the lead and the precise limits 
of weight of the cup which, as explained at p. 77, note 1, apply to the cups of the other fuzes, 
scarcely apply to this one, at least not to the same extent. They are however properly observed. 
|| 14 threads to the inch, right-handed, cone increasing 1 in 9‘375. The size of the frustrum is 
1*95" in length. l'OOS" in diameter at small end. 7‘213" at large end. 
[VOL. V.] 
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