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"Can the cannon support the shock of the pyroxyle?" asked the reporter, who was not less anxious than Pencroft to try the artillery of Granite House. "I believe so. However," added the engineer, "we will be prudent." The engineer was right in thinking that the guns were of excellent make.
Fortunately this did not happen; and some hours later the projectile-vehicle descended gently into the heart of the cannon and rested on its couch of pyroxyle, a veritable bed of explosive eider-down. Its pressure had no result, other than the more effectual ramming down of the charge in the Columbiad.
The projectile outside was nine feet wide and twelve feet high. In order not to pass the weight assigned the sides had been made a little less thick and the bottom thicker, as it would have to support all the violence of the gases developed by the deflagration of the pyroxyle. Bombs and cylindro-conical howitzers are always made with thicker bottoms.
Harding preferred, therefore, to manufacture pyroxyle, that is to say gun-cotton, a substance in which cotton is not indispensable, as the elementary tissue of vegetables may be used, and this is found in an almost pure state, not only in cotton, but in the textile fiber of hemp and flax, in paper, the pith of the elder, etc.
That the casting of a cannon of 900 feet was impracticable and would not succeed, 2,000 dols. That it would be impossible to load the Columbiad, and that the pyroxyle would ignite spontaneously under the weight of the projectile, 3,000 dols. That the Columbiad would burst at the first discharge, 4,000 dols.
On the other hand, the advantages of pyroxyle consist in this, that it is not injured by damp, that it does not make the gun-barrels dirty, and that its force is four times that of ordinary powder. To make pyroxyle, the cotton must be immersed in the fuming azotic acid for a quarter of an hour, then washed in cold water and dried. Nothing could be more simple.
Barbicane quickly put out the gas and lay down by his companions, and the profound silence was only broken by the ticking of the chronometer marking the seconds. Suddenly a dreadful shock was felt, and the projectile, under the force of six billions of litres of gas, developed by the combustion of pyroxyle, mounted into space. What had happened? What effect had this frightful shock produced?
They were charged with pyroxyle, taking into consideration its explosive power, which, as has been said, is four times that of ordinary powder: the projectile to be fired was cylindroconic. Pencroft, holding the end of the quick-match, stood ready to fire. At Harding's signal, he fired. The shot, passing over the islet, fell into the sea at a distance which could not be calculated with exactitude.
"Nevertheless, to satisfy Maston," resumed the president, "I may tell him that one of our fellow-citizens may be annexed to the study of the celluosity, for collodion, which is one of the principal agents in photography, is simply pyroxyle dissolved in ether to which alcohol has been added, and it was discovered by Maynard, then a medical student."
"Nothing is more simple, certainty," said Morgan. "What is more, pyroxyle is not damaged by moisture, a precious quality in our eyes, as it will take several days to load the cannon. Its inflammability takes place at 170° instead of at 240° and its deflagration is so immediate that it may be fired on ordinary gunpowder before the latter has time to catch fire too." "Perfect," answered the major.
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