THE HISTORY OE EXPLOSIVE AGENTS. 
385 
Careful comparative submarine experiments, in which the explosive force was measured 
by the effects produced on crusher-gauges, have indicated that this dynamite (?'. e. 
nitroglycerine diluted with one third its weight of inert material) is about equal, and 
sometimes a little inferior, in power to gun-cotton ; but in open-air experiments (e. g. 
explosion of freely exposed charges against Avails or timber) the dynamite has been 
observed to be sharper and somewhat more local in its action. These observations 
harmonize with the results of the velocity-determinations with the freely exposed 
trains. 
Dynamite Avas, hoAvever, found to behave very differently from compressed gun-cotton 
Avhen spaces Avere alloAved to intervene between the masses composing a charge which 
is detonated in open air. It Avill be remembered that Avith pieces of gun-cotton 3 inches 
(0-076 m.) in diameter, weighing about 2’5 ounces (78 grms.) each, which were placed 
in a row with intervals of 0-5 inch (-013 m.), detonation was transmitted with a 
A’elocity ranging between 16,000 and 17,000 feet (4864 and 5168 m.) per second, and 
therefore not greatly inferior to the mean rate at which detonation was transmitted by 
similar disks arranged in continuous rows. But Avhen charges of some of the dynamite , 
Avhich had transmitted detonation at a rate of from 19,000 to 21,00 feet (5776 to 6384 
m.), the cartridges forming a continuous row, were separated from each other by spaces 
of 0-5 inch (-013 m.), which were left at the same intervals as in the trains of gun- 
cotton (the weight of the individual masses of both substances being nearly alike), the 
mean rate of progression of the detonation was only 6239 feet (1896-65 m.) per second, 
or less than one third of the lowest velocity observed in the experiments with conti- 
nuous trains of dynamite. The trustAvorthiness of this result was conclusively demon- 
strated by the uniformity of the observed velocities at different parts of a long train of 
the spaced dynamite cartridges, as is shown by the following numbers : — 
Rate of progression of tlie 
detonation per second. 
Between 
0' and 
4'=6591 feet (2003-66 m.) 
55 
4' „ 
8'=6133 „ 
(1864-43 „ ) 
55 
8' „ 
12'= 6159 „ 
(1872-23 „ ) 
55 
12' „ 
16'=6394 „ 
(1943-77 „ ) 
55 
16' „ 
20' = 6552 „ 
(1991-80 „ ) 
55 
20' „ 
24'=5789 „ 
(1759-85 „ ) 
55 
24' „ 
28'=6059 „ 
(1841-93 „ ) 
f. Detonation of nitroglycerine. 
The quantity of nitroglycerine at my disposal for these experiments was limited to a 
few pounds ; it was therefore necessary to devise arrangements for the attainment of 
trustworthy results with comparatively small quantities of material. V-shaped troughs, 
14 feet long and about 2 inches deep in the centre, were constructed of thin sheet-metal, 
and the insulated wires at intervals of 2 feet were passed through, and cemented into, 
MDCCCLXXIV. 3 E 
