THE ROYAL ARTILLERY INSTITUTION. 
427 
The points of difference may be most conveniently explained by arranging 
them under the following heads :— 
(1) Points of difference in the head of the fuze; 
(2) Points of difference in the body of the fuze; 
(3) General dimensions. 
As regards (1) The head of the fuze: The principal difference here consists, 
in the introduction of a gun-metal plug, which is screwed permanently into 
the upper part of the composition bore, flush with the top of the fuze. The 
object of this plug is to close the top of the fuze completely, and so to 
prevent [a] the extinction of the fuze when striking end on, and (b) the 
great acceleration of the rate of burning of the composition which is 
induced by the pressure of the air on an unprotected fuze fixed in the apex 
of a rifled shell.* * * § 
The presence of the plug necessitates a different method of priming. 
Prom the centre of the plug projects downwards a copper pin, round which 
is looped a piece of quickmatch, the ends of this match being passed' 
through two escape holes which are provided in the side of the head for the 
escape of the flame from the burning composition. 
The quickmatch is laid in a groove round the head of the fuze, and is 
covered by a strip of thin sheet copper,f the copper being covered by a 
tape band,J and one end of the copper band being exposed. 
The band and upper part of the fuze are painted black, the top of the 
fuze is varnished with shellac varnish. 
(2) The body of the fuze differs from that of the common fuze principally 
in being lined with a paper§ cylinder This lining serves two purposes, 
1st, In the event of the wood shrinking as it will sometimes do in dry, hot 
* The extent to which this acceleration takes place is indicated bj the fact that the total 
acceleration of the time of burning of a 20-seconds metal time fuze which has no such plug, fired 
in a 64-pr. M.L. shell, is 3 seconds ; i.e. a 20-seconds fuze burns only 17 seconds .—Miniite by 
General Lefroy, 18/7/65 on 75/7/1329. The difference wohld of course be greater in shells haying 
a higher velocity. 
f The copper band is 5*1 // long, •3 // wide, and •002' / thick, the end is tapered slightly. 
J The object of covering the quick-match thus carefully, is not merely to protect the priming 
from moisture, but to secure the fuze against accidental ignition. An experiment was made in the 
Royal Laboratory at Woolwich, in March, 1865, to determine how far the fuzes were secure in 
this respect. The result was satisfactory. The following are the details of the experiment 
Eour 7" B.L. common shells placed upright, and a 10 lbs. cartridge exploded in centre, and this 
repeated a second and third time with same fuzes ; none of the fuzes ignited. 
Eour 7" B.L. common shell placed round a 10 lbs. cartridge, with the fuzes resting on the 
cartridge, a cartridge exploded, this repeated a second and third time. One fuze out of twelve, 
may be expected to light. 
§ “ White wrapping ” paper. The outside of the cylinder is varnished with shellac before being 
placed in the fuze. 
