Cyrus Harding could certainly have fabricated a percussion cap.  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.  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 the air as if by the eruption of a volcano.  The shock produced by the displacing of the air was such, that the rocks of the Chimneys shook.  The settlers, although they were more than two miles from the mine, were thrown on the ground.

They rose, climbed the plateau, and ran towards the place where the bank of the lake must have been shattered by the explosion.

A cheer escaped them!  A large rent was seen in the granite!  A rapid stream of water rushed foaming across the plateau and dashed down a height of three hundred feet on to the beach!

Chapter 18

Cyrus Harding’s project had succeeded, but, according to his usual habit he showed no satisfaction; with closed lips and a fixed look, he remained motionless.  Herbert was in ecstasies, Neb bounded with joy, Pencroft nodded his great head, murmuring these words,—­

“Come, our engineer gets on capitally!”

The nitro-glycerine had indeed acted powerfully.  The opening which it had made was so large that the volume of water which escaped through this new outlet was at least treble that which before passed through the old one.  The result was, that a short time after the operation the level of the lake would be lowered two feet, or more.