In default of fulminate, he could easily obtain a substance similar to guncotton, since he had azotic acid at his disposal.

This substance, pressed in a cartridge, and introduced among the nitro-glycerine, would burst by means of a fuse, 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 nitro-glycerine, 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, while the other lay on the ground several feet distant from the mine.