The Moon-Voyage

CHAPTER VIII.

HIS­TO­RY OF THE CAN­NON.

The res­olu­tions passed at this meet­ing pro­duced a great ef­fect out­side. Some timid peo­ple grew alarmed at the idea of a pro­jec­tile weigh­ing 20,000 lbs. hurled in­to space. Peo­ple asked what can­non could ev­er trans­mit an ini­tial speed suf­fi­cient for such a mass. The re­port of the sec­ond meet­ing was des­tined to an­swer these ques­tions vic­to­ri­ous­ly.

The next evening the four mem­bers of the Gun Club sat down be­fore fresh moun­tains of sand­wich­es and a ver­ita­ble ocean of tea. The de­bate then be­gan.

“My dear col­leagues,” said Bar­bi­cane, “we are go­ing to oc­cu­py our­selves with the con­struc­tion of the en­gine, its length, form, com­po­si­tion, and weight. It is prob­able that we shall have to give it gi­gan­tic di­men­sions, but, how­ev­er great our dif­fi­cul­ties might be, our in­dus­tri­al ge­nius will eas­ily over­come them. Will you please lis­ten to me and spare ob­jec­tions for the present? I do not fear them.”

An ap­prov­ing mur­mur greet­ed this dec­la­ra­tion.

“We must not for­get,” re­sumed Bar­bi­cane, "to what point our yes­ter­day's de­bate brought us; the prob­lem is now the fol­low­ing: how to give an ini­tial speed of 12,000 yards a sec­ond to a shot 108 inch­es in di­am­eter weigh­ing 20,000 lbs.

“That is the prob­lem in­deed,” an­swered Ma­jor El­phin­stone.

“When a pro­jec­tile is hurled in­to space,” re­sumed Bar­bi­cane, “what hap­pens? It is act­ed up­on by three in­de­pen­dent forces, the re­sis­tance of the medi­um, the at­trac­tion of the earth, and the force of im­pul­sion with which it is an­imat­ed. Let us ex­am­ine these three forces. The re­sis­tance of the medi­um--that is to say, the re­sis­tance of the air--is of lit­tle im­por­tance. In fact, the ter­res­tri­al at­mo­sphere is on­ly forty miles deep. With a ra­pid­ity of 12,000 yards the pro­jec­tile will cross that in five sec­onds, and this time will be short enough to make the re­sis­tance of the medi­um in­signif­icant. Let us now pass to the at­trac­tion of the earth--that is to say, to the weight of the pro­jec­tile. We know that that weight di­min­ish­es in an in­verse ra­tio to the square of dis­tances--in fact, this is what physics teach us: when a body left to it­self falls on the sur­face of the earth, it falls 15 feet in the first sec­ond, and if the same body had to fall 257,542 miles--that is to say, the dis­tance be­tween the earth and the moon--its fall would be re­duced to half a line in the first sec­ond. That is al­most equiv­alent to im­mo­bil­ity. The ques­tion is, there­fore, how pro­gres­sive­ly to over­come this law of grav­ita­tion. How shall we do it? By the force of im­pul­sion?”

“That is the dif­fi­cul­ty,” an­swered the ma­jor.

“That is it in­deed,” replied the pres­ident. “But we shall tri­umph over it, for this force of im­pul­sion we want de­pends on the length of the en­gine and the quan­ti­ty of pow­der em­ployed, the one on­ly be­ing lim­it­ed by the re­sis­tance of the oth­er. Let us oc­cu­py our­selves, there­fore, to-​day with the di­men­sions to be giv­en to the can­non. It is quite un­der­stood that we can make it, as large as we like, see­ing it will not have to be moved.”

“All that is ev­ident,” replied the gen­er­al.

“Un­til now,” said Bar­bi­cane, “the longest can­non, our enor­mous Columbi­ads, have not been more than twen­ty-​five feet long; we shall there­fore as­ton­ish many peo­ple by the di­men­sions we shall have to adopt.”

“Cer­tain­ly,” ex­claimed J.T. Mas­ton. “For my part, I ask for a can­non half a mile long at least!”

“Half a mile!” cried the ma­jor and the gen­er­al.

“Yes, half a mile, and that will be half too short.”

“Come, Mas­ton,” an­swered Mor­gan, “you ex­ag­ger­ate.”

“No, I do not,” said the irate sec­re­tary; “and I re­al­ly do not know why you tax me with ex­ag­ger­ation.”

“Be­cause you go too far.”

“You must know, sir,” an­swered J.T. Mas­ton, look­ing dig­ni­fied, “that an ar­tillery­man is like a can­non-​ball, he can nev­er go too far.”

The de­bate was get­ting per­son­al, but the pres­ident in­ter­fered.

“Be calm, my friends, and let us rea­son it out. We ev­ident­ly want a gun of great range, as the length of the en­gine will in­crease the de­ten­tion of gas ac­cu­mu­lat­ed be­hind the pro­jec­tile, but it is use­less to over­step cer­tain lim­its.”

“Per­fect­ly,” said the ma­jor.

“What are the usu­al rules in such a case? Or­di­nar­ily the length of a can­non is twen­ty or twen­ty-​five times the di­am­eter of the pro­jec­tile, and it weighs 235 to 240 times its weight.”

“It is not enough,” cried J.T. Mas­ton with im­petu­os­ity.

“I agree to that, my wor­thy friend, and in fact by keep­ing that pro­por­tion for a pro­jec­tile nine feet wide, weigh­ing 30,000 lbs., the en­gine would on­ly have a length of 225 feet and a weight of 7,200,000 lbs.”

“That is ridicu­lous,” re­sumed J.T. Mas­ton. “You might as well take a pis­tol.”

“I think so too,” an­swered Bar­bi­cane; “that is why I pro­pose to quadru­ple that length, and to con­struct a can­non 900 feet long.”

The gen­er­al and the ma­jor made some ob­jec­tions, but, nev­er­the­less, this propo­si­tion, strong­ly sup­port­ed by the sec­re­tary, was def­inite­ly adopt­ed.

“Now,” said El­phin­stone, “what thick­ness must we give its sides?”

“A thick­ness of six feet,” an­swered Bar­bi­cane.

“You do not think of rais­ing such a mass up­on a gun-​car­riage?” asked the ma­jor.

"That would be su­perb, how­ev­er! said J.T. Mas­ton.

“But im­prac­ti­ca­ble,” an­swered Bar­bi­cane. “No, I think of cast­ing this en­gine in the ground it­self, bind­ing it up with wrought-​iron hoops, and then sur­round­ing it with a thick mass of stone and ce­ment ma­son­ry. When it is cast it must be bored with great pre­ci­sion so as to pre­vent windage, so there will be no loss of gas, and all the ex­pan­sive force of the pow­der will be em­ployed in the propul­sion.”

“Hur­rah! hur­rah!” said Mas­ton, “we have our can­non.”

“Not yet,” an­swered Bar­bi­cane, calm­ing his im­pa­tient friend with his hand.

“Why not?”

“Be­cause we have not dis­cussed its form. Shall it be a can­non, how­itzer, or a mor­tar?”

“A can­non,” replied Mor­gan.

“A how­itzer,” said the ma­jor.

“A mor­tar,” ex­claimed J.T. Mas­ton.

A fresh dis­cus­sion was pend­ing, each tak­ing the part of his favourite weapon, when the pres­ident stopped it short.

“My friends,” said he, “I will soon make you agree. Our Columbi­ad will be a mix­ture of all three. It will be a can­non, be­cause the pow­der-​mag­azine will have the same di­am­eter as the cham­ber. It will be a how­itzer, be­cause it will hurl an obus. Last­ly, it will be a mor­tar, be­cause it will be point­ed at an an­gle of 90°, and that with­out any chance of re­coil; un­al­ter­ably fixed to the ground, it will com­mu­ni­cate to the pro­jec­tile all the pow­er of im­pul­sion ac­cu­mu­lat­ed in its body.”

“Adopt­ed, adopt­ed,” an­swered the mem­bers of the com­mit­tee.

“One ques­tion,” said El­phin­stone, “and will this _canobu­so­mor­tar_ be ri­fled?”

“No,” an­swered Bar­bi­cane. “No, we must have an enor­mous ini­tial speed, and you know very well that a shot leaves a ri­fle less rapid­ly than a smooth-​bore.”

“True,” an­swered the ma­jor.

“Well, we have it this time,” re­peat­ed J.T. Mas­ton.

“Not quite yet,” replied the pres­ident.

“Why not?”

“Be­cause we do not yet know of what met­al it will be made.”

“Let us de­cide that with­out de­lay.”

“I was go­ing to pro­pose it to you.”

The four mem­bers of the com­mit­tee each swal­lowed a dozen sand­wich­es, fol­lowed by a cup of tea, and the de­bate recom­menced.

“Our can­non,” said Bar­bi­cane, “must be pos­sessed of great tenac­ity, great hard­ness; it must be in­fusible by heat, in­dis­sol­uble, and in­oxyd­able by the cor­ro­sive ac­tion of acids.”

“There is no doubt about that,” an­swered the ma­jor, “and as we shall have to em­ploy a con­sid­er­able quan­ti­ty of met­al we shall not have much choice.”

“Well, then,” said Mor­gan, “I pro­pose for the fab­ri­ca­tion of the Columbi­ad the best al­loy hith­er­to known--that is to say, 100 parts of cop­per, 12 of tin, and 6 of brass.”

“My friends,” an­swered the pres­ident, “I agree that this com­po­si­tion has giv­en ex­cel­lent re­sults; but in bulk it would be too dear and very hard to work. I there­fore think we must adopt an ex­cel­lent ma­te­ri­al, but cheap, such as cast-​iron. Is not that your opin­ion, ma­jor?”

“Quite,” an­swered El­phin­stone.

“In fact,” re­sumed Bar­bi­cane, “cast-​iron costs ten times less than bronze; it is eas­ily melt­ed, it is read­ily run in­to sand moulds, and is rapid­ly ma­nip­ulat­ed; it is, there­fore, an econ­omy of mon­ey and time. Be­sides, that ma­te­ri­al is ex­cel­lent, and I re­mem­ber that dur­ing the war at the siege of At­lanta cast-​iron can­non fired a thou­sand shots each ev­ery twen­ty min­utes with­out be­ing dam­aged by it.”

“Yet cast-​iron is very brit­tle,” an­swered Mor­gan.

“Yes, but it pos­sess­es re­sis­tance too. Be­sides, we shall not let it ex­plode, I can an­swer for that.”

“It is pos­si­ble to ex­plode and yet be hon­est,” replied J.T. Mas­ton sen­ten­tious­ly.

“Ev­ident­ly,” an­swered Bar­bi­cane. “I am, there­fore, go­ing to beg our wor­thy sec­re­tary to cal­cu­late the weight of a cast-​iron can­non 900 feet long, with an in­ner di­am­eter of nine feet, and sides six feet thick.”

“At once,” an­swered J.T. Mas­ton, and, as he had done the day be­fore, he made his cal­cu­la­tions with mar­vel­lous fa­cil­ity, and said at the end of a minute--

“This can­non will weigh 68,040 tons.”

“And how much will that cost at two cents a pound?”

“Two mil­lion five hun­dred and ten thou­sand sev­en hun­dred and one dol­lars.”

J.T. Mas­ton, the ma­jor, and the gen­er­al looked at Bar­bi­cane anx­ious­ly.

“Well, gen­tle­men,” said the pres­ident, “I can on­ly re­peat what I said to you yes­ter­day, don't be un­easy; we shall not want for mon­ey.”

Up­on this as­sur­ance of its pres­ident the com­mit­tee broke up, af­ter hav­ing fixed a third meet­ing for the next evening.