264 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
COMBINATION FUSES. 
Tn order to secure a burst of the shrapnel at the desired range, or 
in case a burst in the air is not secured, to obtain a burst upon 
impact with the ground, there is carried on the head of each projectile 
a combination fuse of the general character shown in the illustration 
(fig. 6). This contains a concussion plunger which, by means of the 
shock of discharge fires a primer, and thus ignites a tram or ring of 
compressed powder which, after burning a prearranged distance as 
determined by the setting of the fuse, transmits the flame to the 
powder at the base of the shrapnel. Upon the ignition of that 
charge, the fuse is driven off and the balls expelled as previously 
described. There is provided a second plunger—percussion—which 
moves forward on impact, and, in case the shrapnel has not already 
exploded, fires a primer that transmits a flame to the base charge 
with resultant burst. The time tram rmgs which determine the 
interval between the projectiles leavmg the gun and the pomt of 
burst in the air are usually in pairs and so arranged that one of them 
is readily movable with respect to the other, this movement being 
secured through the operation of a device called a ‘‘fuse setter.” 
This device is adjusted in accordance with the known or supposed 
range to the enemy, and the fuse set accordingly by merely inserting 
the projectile into the fuse setter and turning the projectile or the 
fuse setter until the movement is automatically stopped. The burst 
is usually timed to occur a few yards above the ground and a short 
distance in front of the enemy’s position. 
HIGH-EXPLOSIVE SHRAPNEL. 
A third type of projectile combining the principles of both the 
high-explosive shell and the common shrapnel has come into use to 
some extent within the past four or five years, this projectile being 
known as a high-explosive shrapnel. In this type the head carries 
a high explosive charge, and the matrix surrounding the balls is a 
high explosive capable of being detonated by the detonation of the 
head. ‘This projectile carries a.combination fuse and a base charge 
as does the common shrapnel. For use as such the head and balls 
are expelled without a detonation occurring, the matrix serving to 
produce smoke as does that of the common shrapnel. The head con- 
tinues in flight and detonates upon impact, the power being sufficient 
to put out of action a shielded gun in case it strikes the shield. If 
the projectile strikes without having functioned as common shrapnel, 
the head and matrix detonate together, thus giving the effect of the 
high-explosive shell. The explosive commonly used in the head and 
as a matrix in this class of ammunition is trinitrotoluol together with 
the fulminate or other similar material needed to start the deto- 
