THE HISTORY OF EXPLOSIVE AGENTS. 
355 
which the very light tuft of wool opposes to the transmission of force through the tube 
could modify its action to the extent described ; the experiments with silver fulminate 
detailed in Table II. appear, however, to demonstrate conclusively that a slight 
retardation of the velocity of the gas-wave, or the expenditure of force in overcoming 
what appears to be only minute obstacles to the unimpeded transmission of the wave, 
suffices to interfere most materially with the transmission of detonation. 
The interposition of a loosely fitting diaphragm of thin unsized paper between the 
“ detonator ” of silver fulminate and a charge of that substance inserted into the other 
extremity of a glass tube of a particular diameter and 1 metre long, prevented the 
transmission of detonation through the tube of that length until the quantity of ful- 
minate employed as the initiative “ detonator” was about five times that required, of 
the same fulminate, to transmit detonation under the same conditions, but with 
omission of the paper diaphragm. But it is not only by such an expenditure of force 
as is involved in overcoming the resistance which the latter opposes to the free passage 
of 'the gas-wave that the transmission of detonation is greatly impeded; the retardation 
in velocity which the gas-column may sustain in consequence of the friction established 
between it and particles of a fine powder attached to the sides of the glass tube will also 
greatly reduce the distance through which detonation of any given description and 
magnitude will be transmitted. In experiment 22 (in the foregoing Table) much of 
the French chalk, which was loosely attached to the interior of the tube, was carried 
away by the rush of gas; and a similar result, though to a diminished extent, was 
observed in experiments 23 and 24 : yet the roughness of the interior surface of the 
tube was still sufficient, in experiment 25, to prevent the detonation of 06 grain (0-039 
grm.) of silver fulminate from detonating the fulminate in the opposite extremity of 
the tube only 14 inches (0*36 metre) long ; while a corresponding amount of the same 
batch of fulminate induced detonation through a glass tube of the same diameter, 
35 inches (0-9 metre) long, presenting the usual smooth inner surface. 
Discrepancies which were not unfrequently observed in results obtained with wrought- 
iron tubes in the experiments upon a larger scale with mercuric fulminate and with 
gun-cotton, were now clearly traceable to differences in the degree of roughness of the 
inner surface of the tubes, and to the consequent variation in the resistance opposed by 
those surfaces to the passage of the gas-wave. Moreover, the above results obtained 
with the glass tube coated inside with powder suggested some experiments which 
clearly demonstrated that the great difference observed (as shown in Table I.) in the 
transmission of detonation by tubes consisting of different materials was, at any rate 
chiefly, ascribable to the resistance which the inner surfaces of those tubes opposed to 
the free rush of gas through them. A paper tube was constructed of the same dimen- 
sions and thickness as those employed in the preceding experiments, but the inner 
surface consisted of glazed paper instead of ordinary brown paper. The interior of this 
tube was not uniformly smooth throughout like the ordinary glass tubes used ; but still 
it presented a marked difference to the paper tubes with rough interior used in the first 
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