croft, relieved by Neb, did so well, that towards four o'clock in the evening, the mine was finished.
Now the question of setting fire to the explosive substance was raised. Generally, nitro-glycerine is ignited by amorces of fulminate, which in bursting cause the explosion. A shock is therefore needed to produce the explosion, for, simply lighted, this substance would burn without exploding.
Cyrus Harding would certainly have been able to fabricate an amorce. In default of fulminate, he could easily obtain a substance similar to gun-cotton, since he had azotic acid at his disposal. This substance, pressed in a cartridge, and introduced amongst the nitro-glycerine, would burst by means of a match, and cause the explosion.
But Cyrus Harding knew that nitro-glycerine would explode by a shock. He resolved to employ this means, and try another way, if this did not succeed.
In fact, the blow of a hammer on a few drops of nitroglycerine, spread out on a hard surface, was enough to create an explosion. But the operator could not be there to give the blow, without becoming a victim to the operation. Harding, therefore, thought of suspending a mass of iron, weighing several pounds, by means of a fiber, to an upright just above the mine. Another long fiber, previously impregnated with sulphur, was attached to the middle of the first, by one end, whilst the other lay on the ground several feet distant from the mine. The second fiber being set on fire, it would burn till it reached the first. This catching fire in its turn, would break, and the mass of iron would fall on the nitro-glycerine. This apparatus being then arranged, the engineer, after having sent his companions to a distance, filled the hole, so that the nitro-glycerine was on a level with the opening; then he threw a few drops of it on the surface of the rock, above which the mass of iron was already suspended.
This done, Harding lit the end of the sulphured fiber, and leaving the place, he returned with his companions to the Chimneys.
The fiber was intended to burn five and twenty minutes, and, in fact, five and twenty minutes afterwards a most tremendous explosion was heard. The island appeared to tremble to its very foundation. Stones were projected in
