“Well, then, go down and fix the charge. Here it is,” said Baldwin, taking from a wooden case an object about eighteen inches long, which resembled a large office-ruler that had been coated thickly with pitch. It was an elongated shell filled to the muzzle with gunpowder. To one end of it was fastened the end of a coil of wire which was also coated with some protecting substance.

As Baldwin spoke Maxwell slowly puffed the last “draw” from his lips and knocked the ashes out of his pipe on the plank, on which he still remained seated while the two supernumeraries busied themselves in completing his toilet for him; one screwing on his helmet, which appeared ridiculously large, the other loading his breast and back with two heavy leaden weights. When fully equipped, the diver carried on his person a weight fully equal to that of his own bulky person.

“Now look here, Mister Edgar, an’ pay partikler attention, Rooney Machowl. This here toobe, made of indyrubber, d’ee see? (‘Yis, sur,’ from Rooney) I fix on, as you perceive, to the back of Maxwell’s helmet. It communicates with that there pump, and when these two men work the pump, air will be forced into the helmet and into the dress down to his very toes. We could bu’st him, if we were so disposed, if it wasn’t for an escape-valve, here close beside the air-toobe, at the back of the helmet, which keeps lettin’ off the surplus air. Moreover, there is another valve, here in front of the breast-plate, which is under the control of the diver, so that he can let air escape by givin’ it a half-turn when the men at the pumps are givin’ him too much, or he can keep it in when they’re givin’ him enough.”

“An’ what does he do,” asked Rooney, with an anxious expression, “whin they give him too little?”

“He pulls on the air-pipe,—as I’ll explain to you in good time—the proper signal for ‘more air.’”

“But what if he forgits, or misremimbers the signal?” asked the inquisitive recruit.

“Why then,” replied Baldwin, “he suffocates, and we pull him up dead, an’ give him decent burial. Keep yourself easy, my lad, an’ you’ll know all about it in good time. I’ll soon give ’ee the chance to suffocate or bu’st yourself accordin’ to taste.”

“Come, cut it short and look alive,” said Maxwell gruffly, as he stood up to permit of a stout rope being fastened to his waist.

“You shut up!” retorted Baldwin.

Having exchanged these little civilities the two divers moved to the side of the barge—Maxwell with a slow ponderous tread.

A short iron ladder dipped from the gunwale of the barge a few feet down into the sea. The diver stepped upon this, turning with his face inwards, descended knee-deep into the water, and then stopped. Baldwin handed him the blasting-charge. At the same moment one of the supernumeraries advanced with the front-glass or bull’s-eye in his hand, and the men at the pumps gave a turn or two to see that all was working well.

“All right?” demanded the supernumerary.

“Right,” responded Maxwell, in a voice which issued sepulchrally from the iron globe.

There are three round windows fitted with thick plate-glass in the helmets to which we refer. The front one is made to screw off and on, and the fixing of this is always the last operation in completing a diver’s toilet.

“Pump away,” said the man, holding the round glass in front of Maxwell’s nose, and looking over his shoulder to see that the order was obeyed. The glass was screwed on, and the man finished off by gravely patting Maxwell in an affectionate manner on the head.

“Why does he pat him so?” asked Edgar, with a laugh at the apparent tenderness of the act.

“It’s a tinder farewell, I suppose,” murmured Rooney, “in case he niver comes up again.”

“It is to let him know that he may now descend in safety,” answered Baldwin. “The pump there is kep’ goin’ from a few moments before the front-glass is screwed on till the diver shows his head above water again—which he’ll do in quarter of an hour or so, for it don’t take long to lay a charge; but our ordinary spell under water, when work is steady, is about four hours—more or less—with perhaps a breath of ten minutes once or twice at the surface when they’re working deep.”

“But why a breath at the surface?” asked Edgar. “Isn’t the air sent down fresh enough?”

“Quite fresh enough, Mister Edgar, but the pressure when we go deep—say ten or fifteen fathoms—is severe on a man if long continued, so that he needs a little relief now and then. Some need more and some less relief, accordin’ to their strength. Maxwell has only gone down fifteen feet, so that he wouldn’t need to come up at all durin’ a spell of work. We’re goin’ to blast a big rock that has bin’ troublesome to us at low water. The hole was driven in it last week. We moored a raft over it and kep’ men at work with a long iron jumper that reached from the rock to the surface of the sea. It was finished last night, and now he’s gone to fix the charge.”

“But I don’t understand about the pressure, sur, at all at all,” said Machowl, with a complicated look of puzzlement; “sure whin I putt my hand in wather I don’t feel no pressure whatsomediver.”

“Of course not,” responded Baldwin, “because you don’t put it deep enough. You must know that our atmosphere presses on our bodies with a weight of about 20,000 pounds. Well, if you go thirty-two feet deep in the sea you get the pressure of exactly another atmosphere, which means that you’ve got to stand a pressure all over your body of 40,000 when you’ve got down as deep as thirty-two feet.”

“But,” objected Rooney, “I don’t fed no pressure of the atmosphere on me body at all.”

“That’s because you’re squeezed by the air inside of you, man, as well as by the atmosphere outside, which takes off the feelin’ of it, an’, moreover, you’re used to it. If the weight of our atmosphere was took off your outside and not took off your inside—your lungs an’ the like,—you’d come to feel it pretty strong, for you’d swell like a balloon an’ bu’st a’most, if not altogether.”

Baldwin paused a moment and regarded the puzzled countenance of his pupil with an air of pity.

“Contrairywise,” he continued, “if the air was all took out of your inside an’ allowed to remain on your outside, you’d go squash together like a collapsed indyrubber ball. Well then, if that be so with one atmosphere, what must it be with a pressure equal to two, which you have when you go down to thirty-two feet deep in the sea? An’ if you go down to twenty-five fathoms, or 150 feet, which is often done, what must the pressure be there?”

“Tightish, no doubt,” said Rooney.

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