348 
ME, P. A. ABEL’S CONTBIBUTIONS TO 
Tubes of the same diameter and thickness, 5 feet (1*52 m.) in length, were next 
employed; the detonation of 20 grains (T2 grm.) and 23 grains (1*3 grm.) inserted in 
one extremity did not inflame the fulminate enclosed in paper and placed in the 
other end ; and the detonation of 25 grains (T62 grm.) also failed in one instance even 
to produce inflammation ; but in other experiments, under apparently the same condi- 
tions, the fulminate at the opposite extremity was either inflamed or exploded, though 
not with the violent action which a perfect detonation of the same quantity of fulminate 
would exert. 
It would appear from these and similar results obtained with mercuric fulminate 
that the amount of the latter required to induce detonation of the same substance, 
under the conditions described, is generally in direct proportion to the length and 
diameter of the tube through which detonation is transmitted, except when its length 
is so reduced as probably to bring the fulminate operated upon within the range of the 
flash of fire, as well as of the blow given by the initiative explosion. 
d. Experiments with mercuric fulminate and gun-cotton. 
It was shown by me, in my former memoir on Explosive Agents*, that 0-32 grm. 
(5 grains) of fulminate, enclosed in a thin metal case, was required to develop the deto- 
nation of compressed gun-cotton, care being taken to secure close contact between it 
and the detonator. In accordance with the fact demonstrated in that memoir, that the 
sharpness of a detonation and its consequent power of developing detonation in other 
masses was dependent upon the degree of confinement or the strength of the envelope 
enclosing the explosive substance, I have since found that only 2 grains (0T3 grm.) of 
the fulminate are required to detonate compressed gun-cotton with certainty , provided 
the case in which it is enclosed be constructed of stout metal (sheet iron), the detonator 
being so applied as to be closely surrounded by the mass to be detonated (i. e. inserted 
into a perforation in the piece of compressed gun-cotton). If there is not close contact 
between the two, a considerable larger proportion of the fulminate, confined as above 
described, is needed to ensure detonation ; and in actual practice, when it may fre- 
quently be difficult to ensure close contact of the detonator with even some small 
portion of the charge to be exploded, it is found advisable to use about 1 gramme 
(15’45 grains) of the fulminate in the detonating fuse. 
In attempts to transmit the detonative force from a confined fulminate-charge (or 
“ detonator ”) to gun-cotton through the agency of tubes, as in the experiments 
described, somewhat remarkable results were obtained. Contrary to expectation, it 
was found impossible to accomplish this result through the medium of a tube 1 inch 
(•025 m.) in diameter and only 1 foot (*304 m.) in length, by the detonation of even 
so large a charge as 108 grains (7 grms.) of fulminate inserted into one extremity, 
the gun-cotton being introduced into the other end. With a charge of 154 grains 
(10 grms.) only partial explosion of the gun-cotton was effected through a tube of 
* Philosophical Transactions, 1869, vol. clix. p. 498. 
