by E. J. Craine
CHAPTER XI
A MONSTER CANNON
Tom, dressing hastily, read the account in the Paris paper of the fall,in an outlying section of the city, of one of the German shells thatfailed to explode. It was being examined by the military authorities, itwas stated, with a view to finding out what sort of gun fired it, sothat measures might be taken to blow up the piece or render it uselessto the enemy.
"That sounds good to me," said Tom, as they made a hasty breakfast."This is getting down to a scientific basis. An unexploded shell oughtto give 'em a line on the kind of gun that fired it."
"The only trouble," said Jack, "is that the shell may go off when theyare examining it."
"Oh, trust the French ordnance experts not to let a thing like thathappen," said Tom. "Now let's go to it."
It was fortunate that Tom and Jack wore the uniforms that had soendeared them to France, or they might have had difficulty in gainingadmittance to the bureau where the unexploded shell was under processof investigation. But when they first applied, their request wasreferred to a grizzled veteran who smiled kindly at them, patted them onthe shoulders, called them the saviors of France, and ushered them intothe ordnance department, where special deputies were in conference.
"Yes, we have one of the Boche shells," said an officer, who spokeEnglish fluently, for which Tom and Jack were glad. They could speak andunderstand French, but in a case like this, where they wanted a detailedand scientific explanation, their own tongue would better serve them.
"And can you tell from what sort of gun it comes?" asked Tom.
"It was fired from a monster cannon," was the answer. "That is a cannonnot so much a monster in bore, as in length and in its power to impel amissile nearly eighty miles."
"Can it be done?" asked Jack.
"It has been done!" exclaimed Major de Trouville, the officer who wasdetailed to talk to the boys "It has been done. That is the gun that hasbeen bombarding Paris."
"But, from a military standpoint," began Tom, "is it--"
"It is utterly useless," was the quick answer. "Come, I will show youthe shell."
He led them to an apartment set aside for the testing of explosives andworking out ordnance problems, and there on a table, around which satmany prominent French officials, was the German shell--the "dud," asJack had called it.
"The charge has been drawn," explained Major de Trouville, "so there isno danger. And we have determined that the manner in which shots reachParis from a distance of from seventy to eighty miles is by the use of asub-calibre missile."
"A sub-calibre?" murmured Tom.
"Yes. You know, in general, that the more powder you use, and the largerthe surface of the missile which receives it, the greater distance itcan be thrown, providing your angle of elevation is proper."
The boys understood this much, in theory at least.
"Well," went on the major, "while that is true, there is a limit to it.That is to say you could go on using powder up to hundreds of pounds inyour cannon, but when you get to a certain point you have to so increasethe length of the gun, and the size of the breech to make it withstandthe terrific pressure of gases, that it is impracticable to go anyfurther. So, also, in the case of the shell. If you make it too large,so as to get a big surface area for the gases of the burning powder toact upon, you get your shell too heavy to handle.
"Now of course the lighter a missile is, the farther it will go, incomparison to a heavy one with the same force behind it. But you can notget lightness and sufficient resistance to pressure without size, andhere is where the sub-calibre comes in."
"In other words the Germans have been firing a shell within a shell,"broke in another officer.
"Exactly," said Major de Trouville. "The Germans have evolved a big gun,that is big as regards length, to enable the missile they fire from itto gain enough impulse from the powder. But the missile would be toolarge to travel all the way to Paris. So they use two. The inner one isthe one that really gets here and explodes."
"What becomes of the outer?" asked Jack.
"It is a sort of container, or collar, and falls off soon after theshell leaves the big gun. If you will imagine a sort of bomb shell beingenclosed in an iron case, the whole being put in a gun and fired, youwill better get the idea. The outer case is made in two or more pieces,and soon after it is shot out it falls away, leaving the smaller missileto travel on. But here is where the cunning of the invention comes in.The smaller missile has all the impetus given the larger one, butwithout its weight. In consequence it can travel through eighty miles ofatmosphere, finally reaching Paris, where it explodes."
"Wonderful!" exclaimed Jack.
"And yet it is merely the adaptation of an old theory," went on themajor. "We have known of the sub-calibre theory for years, but it is notpracticable. So we did not try it. The cost is too great for the amountof military damage done. And this shell, as you will see, is composed oftwo parts, each with a separate explosive chamber, each containing, aswe discovered, a different sort of explosive. In this way if one did notgo off, the other would, and so set off the one that failed. It is veryclever, but we shall be more clever."
"That's right!" chimed in a chorus of fellow officers.
"We'll find the gun and destroy it--or all of them if they have morethan one, as they probably have," went on the major.
He showed the boys where the shell had chambers for the time fuses towork, much as in a shrapnel shell, which can be set to go off so manyminutes or so many seconds after it reaches its objective point.
"And so the great question is settled by the failure of this shell toexplode," went on the major. "As soon as we saw it, and noted theabsence of the rifling groove marks, we knew it must have been asub-calibre matter. The rest was easy to figure out.
"Some of us thought there might be a big airship, stationed high abovethe clouds, dropping bombs. Others inclined to the theory of a doubleshell; that is, after one had been fired from the cannon it wouldtravel, say, half way and then explode a charge which would impelanother shell toward Paris. A sort of cannon within a cannon, so tospeak. But this is not so. Nor did the theory of a shell with a sort ofpropeller device, like that of a torpedo, prove to be right. It is muchsimpler--just sub-calibre work."
"And what is going to be done about it?" asked Tom. "I mean how can themonster cannon be silenced?"
"Ah, that is a matter we are taking up now," was the answer of Major deTrouville. "I fancy we shall have to call on you boys for a solution ofthat problem."
"On us?" exclaimed Jack.
"Well, I mean on the aircraft service. It will be their task to searchout this great German cannon for us, to enable our gunners to destroyit. Or it may be that it will have to be bombed from an aeroplane."
"That's the task I'd like all right!" cried Tom, with shining eyes.
"Same here!" echoed Jack. "Do you suppose we'll get a chance?" he askedeagerly.
"You may," was the reply. "It may take all the resources of our airmento destroy this terror of the Germans. But it will be done, never fear!"
"_Vive la France!_" cried his companions, and there was a cheer in whichTom and Jack joined.
And so a part of the secret was discovered. It was a monster cannon thatwas devastating Paris. A great gun, the construction of which could onlybe guessed at. But it must be destroyed! That was certain!
