Tl-IE HISTOEY OF EXPLOSIVE AGENTS. 
381 
from mass to mass of dry compressed gun-cotton (the individual masses being in actual 
contact with each other) is between seventeen and twenty thousand feet (5168 m. and 
6080 m.) per second, and that the rapidity of transmission is affected by the compactness 
or rigidity of the masses of gun-cotton, but not importantly by a difference in the form 
and arrangement of the individual masses of gun-cotton, nor by very considerable varia- 
tions in their weight. 
b. Detonation of dry gun-cotton , with spaces intervening between the masses. 
A few experiments were made for the purpose of ascertaining to what extent the 
rate of transmission of detonation Avas affected by leaving small spaces between masses 
of compressed gun-cotton of a particular size, the spaces being insufficient to arrest 
detonation. Disks 3 inches in diameter, and ranging in weight between 2-3 and 2-6 
ounces (7T76 to 8T1 grms.), were placed in a line with intervening spaces of 0-5 inch 
(•013 m.) between each disk. The train Avas 28 feet (8’51 m.)long, but the detonation 
stopped short at 22 feet, there being at this point a somewhat light and comparatively 
spongy disk. The mean velocity of the detonation Avas =16,935 feet (5080 ’5 m.) per 
second, the rate of transmission being 15,606 feet (4681-8 m.) per second in the first 
four feet, and 16,573 (497T9 m.) in the last four feet of the train. A second experiment 
Avith the same description of disks, selected so as to present no great difference in weight 
and compactness, the disks being placed, as before, 0'5 inch (‘013 m.) apart, in a row 
28 feet (8 ’51 m.) long, gave results closely agreeing with the above, the entire train 
being, however, detonated in this instance. The mean velocity of the detonation Avas 
= 16,776 (5032-8 m.), the rate of transmission being 15,676 feet (4702-8 m.) per 
second in the first four feet and 16,218 (4865-4 m.) in the last four. The observations 
recorded of the progress of detonation along the last 16 feet of this train afforded an 
excellent illustration of the uniformity of the rate of transmission, even if the disks are 
spaced, and of the accuracy attainable by the method of observation employed. 
Eate of transmission of detonation 
per second. 
BetAveen 12' and 16'=16,815 feet (5044-5 m.). 
„ 16' „ 20'=16,692 „ (5007-6 „ ). 
„ 20' „ 24'= 16,634 „ (4990-2 „ ). 
„ 24' „ 28'=16,218 „ (4865-4,,).., 
In a third experiment, with a row of disks of the same dimensions as the foregoing, 
but the weight of which ranged between 3-75 (117 grms.) and 4 ounces (124-8 grms.), 
they were separated from each other by spaces of 0-75 inch (-0189 m.). Detonation 
was transmitted more rapidly than by the lighter disks (2-7 ounces= 84-24 grms.), which 
Avere separated by spaces of 0’5 inch (-013 m.); the rate of travel in the last four feet 
happened to be identical Avith that in the first four, but the records obtained in the 
intermediate distances exhibited more considerable fluctuations than usual, as though 
