"I find," he continued, "that the air pressure is not too high for safety.Proper examinations for carbon dioxide are made, and the amount in the air is not excessive.The shifts are not even as long as those prescribed by the law.The medical inspection is quite adequate and as for the time taken in coming out through the locks the rules are stringent."A look of relief crossed the face of Orton at this commendation of his work, followed by a puzzled expression that plainly indicated that he would like to know what was the matter, if all the crucial things were all right.
"But," resumed Kennedy, "the bends are still hitting the men, and there is no telling when a fire or a blow-out may occur in any of the eight headings that are now being pushed under the river.Quite often the work has been delayed and the tunnel partly or wholly flooded.Now, you know the theory of the bends.It is that air - mostly the nitrogen in the air - is absorbed by the blood under the pressure.In coming out of the 'air' if the nitrogen is not all eliminated, it stays in the blood and, as the pressure is reduced, it expands.It is just as if you take a bottle of charged water and pull the cork suddenly.The gas rises in big bubbles.
Cork it again and the gas bubbles cease to rise and finally disappear.If you make a pin-hole in the cork the gas will escape slowly, without a bubble.You must decompress the human body slowly, by stages, to let the super-saturated blood give up its nitrogen to the lungs, which can eliminate it.Otherwise these bubbles catch in the veins, and the result is severe pains, paralysis, and even death.Gentlemen, I see that I am just wasting time telling you this, for you know it all well.But consider."Kennedy placed an empty corked flask on the table.The others regarded it curiously, but I recalled having seen it in the tunnel.
"In this bottle," explained Kennedy, "I collected some of the air from the tunnel when I was down there this morning.I have since analysed it.The quantity of carbon dioxide is approximately what it should be - not high enough of itself to cause trouble.But,"he spoke slowly to emphasise his words, " I found something else in that air beside carbon dioxide.""Nitrogen?" broke in Orton quickly, leaning forward.
"Of course; it is a constituent of air.But that is not what I mean.""Then, for Heaven's sake, what did you find?" asked Orton.
"I found in this air," replied Kennedy, "a very peculiar mixture - an explosive mixture.""An explosive mixture?" echoed Orton.
"Yes, Jack, the blow-outs that you have had at the end of the tunnel were not blow-outs at all, properly speaking.They were explosions."We sat aghast at this revelation.
"And, furthermore," added Kennedy, "I should, if I were you, call back all the men from the tunnel until the cause for the presence of this explosive mixture is discovered and remedied."Orton reached mechanically for the telephone to give the order, but Taylor laid his hand on his arm."One moment, Orton," he said.
"Let's hear Professor Kennedy out.He may be mistaken, and there is no use frightening the men, until we are certain.
"Shelton," asked Kennedy, "what sort of flash oil is used to lubricate the machinery?""It is three-hundred-and-sixty-degree Fahrenheit flash test," he answered tersely.
"And are the pipes leading air down into the tunnel perfectly straight?""Straight?
"Yes, straight - no joints, no pockets where oil, moisture, and gases can collect.""Straight as lines, Kennedy," he said with a sort of contemptuous defiance.
They were facing each other coldly, sizing each other up.Like a skilful lawyer, Kennedy dropped that point for a moment, to take up a new line of attack.
"Capps," he demanded, turning suddenly, "why do you always call up on the telephone and let some one know when you are going down in the tunnel and when you are coming out?""I don't," replied Capps, quickly recovering his composure.
"Walter," said Craig to me quietly, "go out in the outer office.
Behind the telephone switchboard you will find a small box which you saw me carry in there this morning and connect with the switchboard.Detach the wires, as you saw me attach them, and bring it here."No one moved, as I placed the box on a drafting-table before them.
Craig opened it.Inside he disclosed a large disc of thin steel, like those used by some mechanical music-boxes, only without any perforations.He connected the wires from the box to a sort of megaphone.Then he started the disc revolving.
Out of the little megaphone horn, sticking up like a miniature talking-machine, came a voice: Number please.Four four three o, Yorkville.Busy, I'll call you.Try them again, Central.Hello, hello, Central - "Kennedy stopped the machine."It must be further along on the disc," he remarked."This, by the way, is an instrument known as the telegraphone, invented by a Dane named Poulsen.It records conversations over a telephone on this plain metal disc by means of localised, minute electric charges."Having adjusted the needle to another place on the disc he tried again."We have here a record of the entire day's conversations over the telephone, preserved on this disc.I could wipe out the whole thing by pulling a magnet across it, but, needless to say, I wouldn't do that - yet.Listen."This time it was Capps speaking."Give me Mr.Shelton.Oh, Shelton, I'm going down in the south tube with those men Orton has sent nosing around here.I'll let you know when I start up again.Meanwhile - you know - don't let anything happen while I am there.Good-bye."Capps sat looking defiantly at Kennedy, as he stopped the telegraphone.
