THE llOYAL AKTlLLEfiY INSTITUTION. 
79 
The position of the movable parts of the fuze, i.e. cone plug, ball and 
steady plug, is thus shifted to one nearer the bottom of the fuze, by so much 
as the lead cup has flattened, and all re-action is checked by the cup flattening 
round the studs of the bottom and cone plugs, these parts being thus 
securely riveted, as it were, to the bottom of the fuze. 
The great use of the steady plug will now appear :•—It serves, as its name 
implies, to steady the ball at the moment of the shock of discharge; in its 
absence the ball, being unsupported at the top would fall on the flattening 
of the lead cup on to its side, and in proportion to the violence with which 
the detonating composition would thus be brought into contact with the 
sides of the fuze would premature explosions more or less certainly result. * 1 
After the shock of discharge the steady plug is of no further use; the 
rotation or movement of the shell disengages it from the ball, 2 which 
rests during the flight of the shell within the chamber of the fuze. On the 
shell striking an object the ball is thrown forward with a force proportional 
to the momentum of the shell and the violence of the shock ; the detonating 
composition being thus brought into violent contact with some part of the 
interior of the fuze is exploded, and the flame passes through the fire holes 
in the cone and bottom plugs into the shell. 
One or two points which do not properly connect themselves with a 
description of the construction or directly with the action of the fuze require 
explanation. 
It has been explained that the studs on the cone and bottom plugs serve 
to prevent re-action, they also serve by their form to prevent the lead cup 
from flattening over the fire holes which would thus be closed and all. 
communication between the interior of the fuze and shell cut off. 
The reason for making the ball; cone and steady plugs of a harder alloy 
than the rest of the fuze is as follows : In the case of the ball, if the pro¬ 
jections were not made of a certain strength, they would yield under the shock 
of a heavy discharge and pfemature explosion would result. The required 
strength can only be given by increasing the size of the projections or by 
making them of a stronger material. To increase the size would increase 
what may be considered as the dead points of the ball; 3 and the other 
alternative, that of making the projections and consequently the whole ball of 
a harder alloy, ivas therefore adopted. 
As regards the cone and steady plugs, these if made of soft material, 
would be liable to yield under a heavy shock, and they are therefore brought 
to the requisite strength by employing a harder alloy. 
the consequent non-action of the fuze under low charges. The limits are (uncovered) from 140 to 
125 grains ; or (covered) from 146 to 134 grains. 
1 It must be remembered that the position of the fuze in the gun is with its longer axis, not as 
it has been placed throughout the above description, vertical, but horizontal; there would thus be 
no chance of the ball balancing itself on the cone plug in the absence of the steady plug. It would 
inevitably fall against the side of the fuze. 
2 See p. 82 respecting the uncertainty of action of these fuzes with B.L. rifled guns, and the 
^causes of this uncertainty. 
3 Since being uncovered with detonating composition no action could result from the impact 
of one of these projections on the inside of the fuze* 
