THE ROYAL ARTILLERY INSTITUTION. 
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angular pieces of brass [ABCD, Eig. 6). Holes are drilled at F and F } and 
platina wires about £ in. long soldered into them, so as to project equally on 
both sides. At C and D two other holes are drilled, and pieces of brass 
wire, bent into the form of a hook, fixed in. They are intended to fasten 
the threads which press down the spring and are broken by the passage of the 
bullet, and should therefore be at a less distance apart than the bore of the 
carbine, in order to prevent the shot slipping through without breaking a 
thread. Strips of copper or brass are bent in the form shown at G (Fig. 6), 
and brazed at the corners. Inside are soldered small platina discs, at the 
same distance apart as the points E and F. The various pieces are screwed 
on to a board \ in. thick and about 4 ins. wide (as in Eig. 7), and 
Eig. 7. 
binding screws attached at both ends. As the threads require to be so close 
together, weights become inconvenient for- pressing down the springs, and a 
good substitute I have found to be silk-covered elastic, which by its elasticity 
keeps the springs in perfect contact. It will be evident from the drawing in 
Eig. 7 that when the springs are all pressed down by the threads and elastic, 
the breaking of any one will cause the current to be momentarily interrupted, 
but again renewed almost immediately. 
On trying the screens, by fastening short wires (less than 3 ft.) from 
the binding screws to the primary wire of a coil, however much battery 
power was put on, no induced spark could be obtained—not even the of 
an inch, although the coil used in the ordinary manner was capable of 
producing a spark fully fin. long. It was proved clearly that the con¬ 
nections were in perfect order, and that this failure did not arise from the 
resistance of the wires or screens, as a strong current was passing freely at the 
time. And here would have been an end of the chronograph, had not a happy 
thought struck me, after nearly a month spent in experimenting, which 
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