Nothing was easier than to place this cartridge in a corner of the cabin, so that it would blow in the deck and tear away the framework of the hull.
But to obtain the explosion it was necessary to adjust the fulminating cap with which the cartridge was fitted.

This was the most delicate part of the operation, for the explosion would have to be carefully timed, so as not to occur too soon or too late.
Uncle Prudent had carefully thought over the matter.

His conclusions were as follows.

As soon as the fore propeller was repaired the aeronef would resume her course to the north, and that done Robur and his crew would probably come aft to put the other screw into order.
The presence of these people about the cabin might interfere with his plans, and so he had resolved to make a slow match do duty as a time-fuse.
"When I got the cartridge," said he to Phil Evans, "I took some gunpowder as well.

With the powder I will make a fuse that will take some time to burn, and which will lead into the fulminate.