CHAPTER IX
THE QUESTION OF THE POWDERS
There remained for consideration merely the question of powders.The public awaited with interest its final decision. The sizeof the projectile, the length of the cannon being settled, whatwould be the quantity of powder necessary to produce impulsion?
It is generally asserted that gunpowder was invented in thefourteenth century by the monk Schwartz, who paid for his granddiscovery with his life. It is, however, pretty well provedthat this story ought to be ranked among the legends of themiddle ages. Gunpowder was not invented by any one; it was thelineal successor of the Greek fire, which, like itself, wascomposed of sulfur and saltpeter. Few persons are acquaintedwith the mechanical power of gunpowder. Now this is preciselywhat is necessary to be understood in order to comprehend theimportance of the question submitted to the committee.
A litre of gunpowder weighs about two pounds; during combustionit produces 400 litres of gas. This gas, on being liberated andacted upon by temperature raised to 2,400 degrees, occupies aspace of 4,000 litres: consequently the volume of powder is tothe volume of gas produced by its combustion as 1 to 4,000.One may judge, therefore, of the tremendous pressure on thisgas when compressed within a space 4,000 times too confined.All this was, of course, well known to the members of the committeewhen they met on the following evening.
The first speaker on this occasion was Major Elphinstone, whohad been the director of the gunpowder factories during the war.
"Gentlemen," said this distinguished chemist, "I begin withsome figures which will serve as the basis of our calculation.The old 24-pounder shot required for its discharge sixteen poundsof powder."
"You are certain of this amount?" broke in Barbicane.
"Quite certain," replied the major. "The Armstrong cannonemploys only seventy-five pounds of powder for a projectileof eight hundred pounds, and the Rodman Columbiad uses only onehundred and sixty pounds of powder to send its half ton shot adistance of six miles. These facts cannot be called in question,for I myself raised the point during the depositions taken beforethe committee of artillery."
"Quite true," said the general.
"Well," replied the major, "these figures go to prove that thequantity of powder is not increased with the weight of the shot;that is to say, if a 24-pounder shot requires sixteen pounds ofpowder;-- in other words, if in ordinary guns we employ aquantity of powder equal to two-thirds of the weight of theprojectile, this proportion is not constant. Calculate, and youwill see that in place of three hundred and thirty-three poundsof powder, the quantity is reduced to no more than one hundredand sixty pounds."
"What are you aiming at?" asked the president.
"If you push your theory to extremes, my dear major," said J. T.Maston, "you will get to this, that as soon as your shot becomessufficiently heavy you will not require any powder at all."
"Our friend Maston is always at his jokes, even in seriousmatters," cried the major; "but let him make his mind easy, I amgoing presently to propose gunpowder enough to satisfy hisartillerist's propensities. I only keep to statistical factswhen I say that, during the war, and for the very largest guns,the weight of the powder was reduced, as the result ofexperience, to a tenth part of the weight of the shot."
"Perfectly correct," said Morgan; "but before deciding thequantity of powder necessary to give the impulse, I think itwould be as well----"
"We shall have to employ a large-grained powder," continued themajor; "its combustion is more rapid than that of the small."
"No doubt about that," replied Morgan; "but it is verydestructive, and ends by enlarging the bore of the pieces."
"Granted; but that which is injurious to a gun destined toperform long service is not so to our Columbiad. We shallrun no danger of an explosion; and it is necessary that ourpowder should take fire instantaneously in order that itsmechanical effect may be complete."
"We must have," said Maston, "several touch-holes, so as to fireit at different points at the same time."
"Certainly," replied Elphinstone; "but that will render theworking of the piece more difficult. I return then to mylarge-grained powder, which removes those difficulties.In his Columbiad charges Rodman employed a powder as largeas chestnuts, made of willow charcoal, simply dried in cast-iron pans. This powder was hard and glittering, left no traceupon the hand, contained hydrogen and oxygen in large proportion,took fire instantaneously, and, though very destructive, did notsensibly injure the mouth-piece."
Up to this point Barbicane had kept aloof from the discussion;he left the others to speak while he himself listened; he hadevidently got an idea. He now simply said, "Well, my friends,what quantity of powder do you propose?"
The three members looked at one another.
"Two hundred thousand pounds." at last said Morgan.
"Five hundred thousand," added the major.
"Eight hundred thousand," screamed Maston.
A moment of silence followed this triple proposal; it was atlast broken by the president.
"Gentlemen," he quietly said, "I start from this principle, thatthe resistance of a gun, constructed under the given conditions,is unlimited. I shall surprise our friend Maston, then, bystigmatizing his calculations as timid; and I propose to doublehis 800,000 pounds of powder."
"Sixteen hundred thousand pounds?" shouted Maston, leaping fromhis seat.
"Just so."
"We shall have to come then to my ideal of a cannon half a milelong; for you see 1,600,000 pounds will occupy a space of about20,000 cubic feet; and since the contents of your cannon do notexceed 54,000 cubic feet, it would be half full; and the borewill not be more than long enough for the gas to communicate tothe projectile sufficient impulse."
"Nevertheless," said the president, "I hold to that quantityof powder. Now, 1,600,000 pounds of powder will create6,000,000,000 litres of gas. Six thousand millions!You quite understand?"
"What is to be done then?" said the general.
"The thing is very simple; we must reduce this enormous quantityof powder, while preserving to it its mechanical power."
"Good; but by what means?"
"I am going to tell you," replied Barbicane quietly.
"Nothing is more easy than to reduce this mass to one quarter ofits bulk. You know that curious cellular matter whichconstitutes the elementary tissues of vegetable? This substanceis found quite pure in many bodies, especially in cotton, whichis nothing more than the down of the seeds of the cotton plant.Now cotton, combined with cold nitric acid, become transformedinto a substance eminently insoluble, combustible, and explosive.It was first discovered in 1832, by Braconnot, a French chemist,who called it xyloidine. In 1838 another Frenchman, Pelouze,investigated its different properties, and finally, in 1846,Schonbein, professor of chemistry at Bale, proposed its employmentfor purposes of war. This powder, now called pyroxyle, orfulminating cotton, is prepared with great facility by simplyplunging cotton for fifteen minutes in nitric acid, then washingit in water, then drying it, and it is ready for use."
"Nothing could be more simple," said Morgan.
"Moreover, pyroxyle is unaltered by moisture-- a valuableproperty to us, inasmuch as it would take several days to chargethe cannon. It ignites at 170 degrees in place of 240, and itscombustion is so rapid that one may set light to it on the topof the ordinary powder, without the latter having time to ignite."
"Perfect!" exclaimed the major.
"Only it is more expensive."
"What matter?" cried J. T. Maston.
"Finally, it imparts to projectiles a velocity four timessuperior to that of gunpowder. I will even add, that if we mixit with one-eighth of its own weight of nitrate of potassium,its expansive force is again considerably augmented."
"Will that be necessary?" asked the major.
"I think not," replied Barbicane. "So, then, in place of1,600,000 pounds of powder, we shall have but 400,000 pounds offulminating cotton; and since we can, without danger, compress500 pounds
of cotton into twenty-seven cubic feet, the wholequantity will not occupy a height of more than 180 feet withinthe bore of the Columbiad. In this way the shot will have morethan 700 feet of bore to traverse under a force of 6,000,000,000litres of gas before taking its flight toward the moon."
At this juncture J. T. Maston could not repress his emotion; heflung himself into the arms of his friend with the violence ofa projectile, and Barbicane would have been stove in if he hadnot been boom-proof.
This incident terminated the third meeting of the committee.
Barbicane and his bold colleagues, to whom nothing seemedimpossible, had succeeding in solving the complex problems ofprojectile, cannon, and powder. Their plan was drawn up, and itonly remained to put it into execution.
"A mere matter of detail, a bagatelle," said J. T. Maston.