The Moon-Voyage Page 9

  CHAPTER IX.

  THE QUESTION OF POWDERS.

  The question of powder still remained to be settled. The public awaitedthis last decision with anxiety. The size of the projectile and lengthof the cannon being given, what would be the quantity of powdernecessary to produce the impulsion? This terrible agent, of which,however, man has made himself master, was destined to play a part inunusual proportions.

  It is generally known and often asserted that gunpowder was invented inthe fourteenth century by the monk Schwartz, who paid for his greatdiscovery with his life. But it is nearly proved now that this storymust be ranked among the legends of the Middle Ages. Gunpowder wasinvented by no one; it is a direct product of Greek fire, composed, likeit, of sulphur and saltpetre; only since that epoch these mixtures;which were only dissolving, have been transformed into detonatingmixtures.

  But if learned men know perfectly the false history of gunpowder, fewpeople are aware of its mechanical power. Now this is necessary to beknown in order to understand the importance of the question submitted tothe committee.

  Thus a litre of gunpowder weighs about 2 lbs.; it produces, by burning,about 400 litres of gas; this gas, liberated, and under the action of atemperature of 2,400 deg., occupies the space of 4,000 litres. Therefore thevolume of powder is to the volume of gas produced by its deflagration as1 to 400. The frightful force of this gas, when it is compressed into aspace 4,000 times too small, may be imagined.

  This is what the members of the committee knew perfectly when, the nextday, they began their sitting. Major Elphinstone opened the debate.

  "My dear comrades," said the distinguished chemist, "I am going to beginwith some unexceptionable figures, which will serve as a basis for ourcalculation. The 24-lb. cannon-ball, of which the Hon. J.T. Maston spokethe day before yesterday, is driven out of the cannon by 16 lbs. ofpowder only."

  "You are certain of your figures?" asked Barbicane.

  "Absolutely certain," answered the major. "The Armstrong cannon onlyuses 75 lbs. of powder for a projectile of 800 lbs., and the RodmanColumbiad only expends 160 lbs. of powder to send its half-ton bulletsix miles. These facts cannot be doubted, for I found them myself in thereports of the Committee of Artillery."

  "That is certain," answered the general.

  "Well," resumed the major, "the conclusion to be drawn from thesefigures is that the quantity of powder does not augment with the weightof the shot; in fact, if a shot of 24 lbs. took 16 lbs. of powder, and,in other terms, if in ordinary cannons a quantity of powder weighingtwo-thirds of the weight of the projectile is used, this proportion isnot always necessary. Calculate, and you will see that for the shot ofhalf a ton weight, instead of 333 lbs. of powder, this quantity has beenreduced to 116 lbs. only.

  "What are you driving at?" asked the president.

  "The extreme of your theory, my dear major," said J.T. Maston, "wouldbring you to having no powder at all, provided your shot weresufficiently heavy."

  "Friend Maston will have his joke even in the most serious things,"replied the major; "but he need not be uneasy; I shall soon propose aquantity of powder that will satisfy him. Only I wish to have itunderstood that during the war, and for the largest guns, the weight ofthe powder was reduced, after experience, to a tenth of the weight ofthe shot."

  "Nothing is more exact," said Morgan; "but, before deciding the quantityof powder necessary to give the impulsion, I think it would be well toagree upon its nature."

  "We shall use a large-grained powder," answered the major; "itsdeflagration is the most rapid."

  "No doubt," replied Morgan; "but it is very brittle, and ends bydamaging the chamber of the gun."

  "Certainly; but what would be bad for a gun destined for long servicewould not be so for our Columbiad. We run no danger of explosion, andthe powder must immediately take fire to make its mechanical effectcomplete."

  "We might make several touchholes," said J.T. Maston, "so as to set fireto it in several places at the same time."

  "No doubt," answered Elphinstone, "but that would make the working of itmore difficult. I therefore come back to my large-grained powder thatremoves these difficulties."

  "So be it," answered the general.

  "To load his Columbiad," resumed the major, "Rodman used a powder ingrains as large as chestnuts, made of willow charcoal, simply rarefiedin cast-iron pans. This powder was hard and shining, left no stain onthe hands, contained a great proportion of hydrogen and oxygen,deflagrated instantaneously, and, though very brittle, did not muchdamage the mouthpiece."

  "Well, it seems to me," answered J.T. Maston, "that we have nothing tohesitate about, and that our choice is made."

  "Unless you prefer gold-powder," replied the major, laughing, whichprovoked a threatening gesture from the steel hook of his susceptiblefriend.

  Until then Barbicane had kept himself aloof from the discussion; helistened, and had evidently an idea. He contented himself with sayingsimply--

  "Now, my friends, what quantity of powder do you propose?"

  The three members of the Gun Club looked at one another for the space ofa minute.

  "Two hundred thousand pounds," said Morgan at last.

  "Five hundred thousand," replied the major.

  "Eight hundred thousand," exclaimed J.T. Maston.

  This, time Elphinstone dared not tax his colleague with exaggeration. Infact, the question was that of sending to the moon a projectile weighing20,000 lbs., and of giving it an initial force of 2000 yards a second. Amoment of silence, therefore, followed the triple proposition made bythe three colleagues.

  It was at last broken by President Barbicane.

  "My brave comrades," said he in a quiet tone, "I start from thisprinciple, that the resistance of our cannon, in the given conditions,is unlimited. I shall, therefore, surprise the Honourable J.T. Mastonwhen I tell him that he has been timid in his calculations, and Ipropose to double his 800,000 lbs. of powder."

  "Sixteen hundred thousand pounds!" shouted J.T. Maston, jumping out ofhis chair.

  "Quite as much as that."

  "Then we shall have to come back to my cannon half a mile long."

  "It is evident," said the major.

  "Sixteen hundred thousand pounds of powder," resumed the Secretary ofCommittee, "will occupy about a space of 22,000 cubic feet; now, as yourcannon will only hold about 54,000 cubic feet, it will be half full, andthe chamber will not be long enough to allow the explosion of the gas togive sufficient impulsion to your projectile."

  There was nothing to answer. J.T. Maston spoke the truth. They alllooked at Barbicane.

  "However," resumed the president, "I hold to that quantity of powder.Think! 1,600,000 pounds of powder will give 6,000,000,000 litres ofgas."

  "Then how is it to be done?" asked the general.

  "It is very simple. We must reduce this enormous quantity of powder,keeping at the same time its mechanical power."

  "Good! By what means?"

  "I will tell you," answered Barbicane simply.

  His interlocutors all looked at him.

  "Nothing is easier, in fact," he resumed, "than to bring that mass ofpowder to a volume four times less. You all know that curious cellularmatter which constitutes the elementary tissues of vegetables?"

  "Ah!" said the major, "I understand you, Barbicane."

  "This matter," said the president, "is obtained in perfect purity indifferent things, especially in cotton, which is nothing but the skin ofthe seeds of the cotton plant. Now cotton, combined with cold nitricacid, is transformed into a substance eminently insoluble, eminentlycombustible, eminently explosive. Some years ago, in 1832, a Frenchchemist, Braconnot, discovered this substance, which he calledxyloidine. In 1838, another Frenchman, Pelouze, studied its differentproperties; and lastly, in 1846, Schonbein, professor of chemistry atBasle, proposed it as gunpowder. This powder is nitric cotton."

  "Or pyroxyle," answered Elphinstone.

  "Or fulminating cotton," replied Morgan.

 
"Is there not an American name to put at the bottom of this discovery?"exclaimed J.T. Maston, animated by a lively sentiment of patriotism.

  "Not one, unfortunately," replied the major.

  "Nevertheless, to satisfy Maston," resumed the president, "I may tellhim that one of our fellow-citizens may be annexed to the study of thecelluosity, for collodion, which is one of the principal agents inphotography, is simply pyroxyle dissolved in ether to which alcohol hasbeen added, and it was discovered by Maynard, then a medical student."

  "Hurrah for Maynard and fulminating cotton!" cried the noisy secretaryof the Gun Club.

  "I return to pyroxyle," resumed Barbicane. "You are acquainted with itsproperties which make it so precious to us. It is prepared with thegreatest facility; cotton plunged in smoking nitric acid for fifteenminutes, then washed in water, then dried, and that is all."

  "Nothing is more simple, certainty," said Morgan.

  "What is more, pyroxyle is not damaged by moisture, a precious qualityin our eyes, as it will take several days to load the cannon. Itsinflammability takes place at 170 deg. instead of at 240 deg. and itsdeflagration is so immediate that it may be fired on ordinary gunpowderbefore the latter has time to catch fire too."

  "Perfect," answered the major.

  "Only it will cost more."

  "What does that matter?" said J.T. Maston.

  "Lastly, it communicates to projectiles a speed four times greater thanthat of gunpowder. I may even add that if 8/10ths of its weight ofnitrate of potash is added its expansive force is still greatlyaugmented."

  "Will that be necessary?" asked the major.

  "I do not think so," answered Barbicane. "Thus instead of 1,600,000 lbs.of powder, we shall only have 400,000 lbs. of fulminating cotton, and aswe can, without danger, compress 500 lbs. of cotton into 27 cubic feet,that quantity will not take up more than 180 feet in the chamber of theColumbiad. By these means the projectile will have more than 700 feet ofchamber to traverse under a force of 6,000,000,000 of litres of gasbefore taking its flight over the Queen of Night."

  Here J.T. Maston could not contain his emotion. He threw himself intothe arms of his friend with the violence of a projectile, and he wouldhave been stove in had he not have been bombproof.

  This incident ended the first sitting of the committee. Barbicane andhis enterprising colleagues, to whom nothing seemed impossible, had justsolved the complex question of the projectile, cannon, and powder. Theirplan being made, there was nothing left but to put it into execution.