The explosive power of this substance is inferior to that of gun-cotton or of dynamite, but far greater than that of ordinary gunpowder; one grain of picric powder producing an effect equal to that of thirteen grains of common powder.

Picrate is easily ignited by any sharp or violent shock, and some gun-priming which we had in our possession would answer the purpose of setting it alight.
The sailors went off at once for their pikes, and Dowlas and his assistants, under the direction of Falsten, who, as an engineer, understood such matters, proceeded to hollow out a mine wherein to deposit the powder.

At first we hoped that everything would be ready for the blasting to take place on the following morning, but when daylight appeared we found that the men, although they had laboured with a will, had only been able to work for an hour at low water and that four tides must ebb before the mine had been sunk to the required depth.
Not until eight o'clock on the morning of the 23rd was the work complete.

The hole was bored obliquely in the rock, and was large enough to contain about ten pounds of explosive matter.

Just as the picrate was being introduced into the aperture, Falsten interposed:-- "Stop," he said, "I think it will be best to mix the picrate with common powder, as that will allow us to fire the mine with a match instead of the gun-priming which would be necessary to produce a shock.