Five Weeks in a Balloon

CHAPTER TENTH.

For­mer Ex­per­iments.–The Doc­tor’s Five Re­cep­ta­cles.–The Gas Cylin­der.– The Calorifere.–The Sys­tem of Ma­noeu­vring.–Suc­cess cer­tain.

“The at­tempt has of­ten been made, gen­tle­men,” said the doc­tor, “to rise and de­scend at will, with­out los­ing bal­last or gas from the bal­loon. A French aero­naut, M. Me­unier, tried to ac­com­plish this by com­press­ing air in an in­ner re­cep­ta­cle. A Bel­gian, Dr. Van Hecke, by means of wings and pad­dles, ob­tained a ver­ti­cal pow­er that would have suf­ficed in most cas­es, but the prac­ti­cal re­sults se­cured from these ex­per­iments have been in­signif­icant.

“I there­fore re­solved to go about the thing more di­rect­ly; so, at the start, I dis­pensed with bal­last al­to­geth­er, ex­cept­ing as a pro­vi­sion for cas­es of spe­cial emer­gen­cy, such as the break­age of my ap­pa­ra­tus, or the ne­ces­si­ty of as­cend­ing very sud­den­ly, so as to avoid un­fore­seen ob­sta­cles.

“My means of as­cent and de­scent con­sist sim­ply in di­lat­ing or con­tract­ing the gas that is in the bal­loon by the ap­pli­ca­tion of dif­fer­ent tem­per­atures, and here is the method of ob­tain­ing that re­sult.

“You saw me bring on board with the car sev­er­al cas­es or re­cep­ta­cles, the use of which you may not have un­der­stood. They are five in num­ber.

“The first con­tains about twen­ty-​five gal­lons of wa­ter, to which I add a few drops of sul­phuric acid, so as to aug­ment its ca­pac­ity as a con­duc­tor of elec­tric­ity, and then I de­com­pose it by means of a pow­er­ful Buntzen bat­tery. Wa­ter, as you know, con­sists of two parts of hy­dro­gen to one of oxy­gen gas.

“The lat­ter, through the ac­tion of the bat­tery, pass­es at its pos­itive pole in­to the sec­ond re­cep­ta­cle. A third re­cep­ta­cle, placed above the sec­ond one, and of dou­ble its ca­pac­ity, re­ceives the hy­dro­gen pass­ing in­to it by the neg­ative pole.

“Stop­cocks, of which one has an ori­fice twice the size of the oth­er, com­mu­ni­cate be­tween these re­cep­ta­cles and a fourth one, which is called the mix­ture reser­voir, since in it the two gas­es ob­tained by the de­com­po­si­tion of the wa­ter do re­al­ly com­min­gle. The ca­pac­ity of this fourth tank is about forty-​one cu­bic feet.

“On the up­per part of this tank is a plat­inum tube pro­vid­ed with a stop­cock.

“You will now read­ily un­der­stand, gen­tle­men, the ap­pa­ra­tus that I have de­scribed to you is re­al­ly a gas cylin­der and blow-​pipe for oxy­gen and hy­dro­gen, the heat of which ex­ceeds that of a forge fire.

“This much es­tab­lished, I pro­ceed to the sec­ond part of my ap­pa­ra­tus. From the low­est part of my bal­loon, which is her­met­ical­ly closed, is­sue two tubes a lit­tle dis­tance apart. The one starts among the up­per lay­ers of the hy­dro­gen gas, the oth­er amid the low­er lay­ers.

“These two pipes are pro­vid­ed at in­ter­vals with strong joint­ings of in­dia-​rub­ber, which en­able them to move in har­mo­ny with the os­cil­la­tions of the bal­loon.

“Both of them run down as far as the car, and lose them­selves in an iron re­cep­ta­cle of cylin­dri­cal form, which is called the heat-​tank. The lat­ter is closed at its two ends by two strong plates of the same met­al.

“The pipe run­ning from the low­er part of the bal­loon runs in­to this cylin­dri­cal re­cep­ta­cle through the low­er plate; it pen­etrates the lat­ter and then takes the form of a he­li­coidal or screw-​shaped spi­ral, the rings of which, ris­ing one over the oth­er, oc­cu­py near­ly the whole of the height of the tank. Be­fore again is­su­ing from it, this spi­ral runs in­to a small cone with a con­cave base, that is turned down­ward in the shape of a spher­ical cap.

“It is from the top of this cone that the sec­ond pipe is­sues, and it runs, as I have said, in­to the up­per beds of the bal­loon.

“The spher­ical cap of the small cone is of plat­inum, so as not to melt by the ac­tion of the cylin­der and blow-​pipe, for the lat­ter are placed up­on the bot­tom of the iron tank in the midst of the he­li­coidal spi­ral, and the ex­trem­ity of their flame will slight­ly touch the cap in ques­tion.

“You all know, gen­tle­men, what a calorifere, to heat apart­ments, is. You know how it acts. The air of the apart­ments is forced to pass through its pipes, and is then re­leased with a height­ened tem­per­ature. Well, what I have just de­scribed to you is noth­ing more nor less than a calorifere.

“In fact, what is it that takes place? The cylin­der once light­ed, the hy­dro­gen in the spi­ral and in the con­cave cone be­comes heat­ed, and rapid­ly as­cends through the pipe that leads to the up­per part of the bal­loon. A vac­uum is cre­at­ed be­low, and it at­tracts the gas in the low­er parts; this be­comes heat­ed in its turn, and is con­tin­ual­ly re­placed; thus, an ex­treme­ly rapid cur­rent of gas is es­tab­lished in the pipes and in the spi­ral, which is­sues from the bal­loon and then re­turns to it, and is heat­ed over again, in­ces­sant­ly.

“Now, the cas­es in­crease 1/480 of their vol­ume for each de­gree of heat ap­plied. If, then, I force the tem­per­ature 18 de­grees, the hy­dro­gen of the bal­loon will di­late 18/480 or 1614 cu­bic feet, and will, there­fore, dis­place 1614 more cu­bic feet of air, which will in­crease its as­cen­sion­al pow­er by 160 pounds. This is equiv­alent to throw­ing out that weight of bal­last. If I aug­ment the tem­per­ature by 180 de­grees, the gas will di­late 180/480 and will dis­place 16,740 cu­bic feet more, and its as­cen­sion­al force will be aug­ment­ed by 1,600 pounds.

“Thus, you see, gen­tle­men, that I can eas­ily ef­fect very con­sid­er­able changes of equi­lib­ri­um. The vol­ume of the bal­loon has been cal­cu­lat­ed in such man­ner that, when half in­flat­ed, it dis­places a weight of air ex­act­ly equal to that of the en­ve­lope con­tain­ing the hy­dro­gen gas, and of the car oc­cu­pied by the pas­sen­gers, and all its ap­pa­ra­tus and ac­ces­sories. At this point of in­fla­tion, it is in ex­act equi­lib­ri­um with the air, and nei­ther mounts nor de­scends.

“In or­der, then, to ef­fect an as­cent, I give the gas a tem­per­ature su­pe­ri­or to the tem­per­ature of the sur­round­ing air by means of my cylin­der. By this ex­cess of heat it ob­tains a larg­er dis­ten­tion, and in­flates the bal­loon more. The lat­ter, then, as­cends in pro­por­tion as I heat the hy­dro­gen.

“The de­scent, of course, is ef­fect­ed by low­er­ing the heat of the cylin­der, and let­ting the tem­per­ature abate. The as­cent would be, usu­al­ly, more rapid than the de­scent; but that is a for­tu­nate cir­cum­stance, since it is of no im­por­tance to me to de­scend rapid­ly, while, on the oth­er hand, it is by a very rapid as­cent that I avoid ob­sta­cles. The re­al dan­ger lurks be­low, and not above.

“Be­sides, as I have said, I have a cer­tain quan­ti­ty of bal­last, which will en­able me to as­cend more rapid­ly still, when nec­es­sary. My valve, at the top of the bal­loon, is noth­ing more nor less than a safe­ty-​valve. The bal­loon al­ways re­tains the same quan­ti­ty of hy­dro­gen, and the vari­ations of tem­per­ature that I pro­duce in the midst of this shut-​up gas are, of them­selves, suf­fi­cient to pro­vide for all these as­cend­ing and de­scend­ing move­ments.

“Now, gen­tle­men, as a prac­ti­cal de­tail, let me add this:

“The com­bus­tion of the hy­dro­gen and of the oxy­gen at the point of the cylin­der pro­duces sole­ly the va­por or steam of wa­ter. I have, there­fore, pro­vid­ed the low­er part of the cylin­dri­cal iron box with a scape-​pipe, with a valve op­er­at­ing by means of a pres­sure of two at­mo­spheres; con­se­quent­ly, so soon as this amount of pres­sure is at­tained, the steam es­capes of it­self.

“Here are the ex­act fig­ures: 25 gal­lons of wa­ter, sep­arat­ed in­to its con­stituent el­ements, yield 200 pounds of oxy­gen and 25 pounds of hy­dro­gen. This rep­re­sents, at at­mo­spher­ic ten­sion, 1,800 cu­bic feet of the for­mer and 3,780 cu­bic feet of the lat­ter, or 5,670 cu­bic feet, in all, of the mix­ture. Hence, the stop­cock of my cylin­der, when ful­ly open, ex­pends 27 cu­bic feet per hour, with a flame at least six times as strong as that of the large lamps used for light­ing streets. On an av­er­age, then, and in or­der to keep my­self at a very mod­er­ate el­eva­tion, I should not burn more than nine cu­bic feet per hour, so that my twen­ty-​five gal­lons of wa­ter rep­re­sent six hun­dred and thir­ty-​six hours of aeri­al nav­iga­tion, or a lit­tle more than twen­ty-​six days.

“Well, as I can de­scend when I please, to re­plen­ish my stock of wa­ter on the way, my trip might be in­def­inite­ly pro­longed.

“Such, gen­tle­men, is my se­cret. It is sim­ple, and, like most sim­ple things, it can­not fail to suc­ceed. The di­la­tion and con­trac­tion of the gas in the bal­loon is my means of lo­co­mo­tion, which calls for nei­ther cum­ber­some wings, nor any oth­er me­chan­ical mo­tor. A calorifere to pro­duce the changes of tem­per­ature, and a cylin­der to gen­er­ate the heat, are nei­ther in­con­ve­nient nor heavy. I think, there­fore, that I have com­bined all the el­ements of suc­cess.”

Dr. Fer­gu­son here ter­mi­nat­ed his dis­course, and was most hearti­ly ap­plaud­ed. There was not an ob­jec­tion to make to it; all had been fore­seen and de­cid­ed.

“How­ev­er,” said the cap­tain, “the thing may prove dan­ger­ous.”

“What mat­ters that,” replied the doc­tor, “pro­vid­ed that it be prac­ti­ca­ble?”