"Wait. I see that this hold and the 'tween-deck are lined with wood. Is that customary in iron ships?"

"Not now. It used to be a notion that an iron skin damaged the cargo; so the first iron ships were ceiled with wood."

"Are there any drains in the 'tween-deck to let water out, in case it gets into that deck from above—a sea, for instance?"

"Yes, always; three or four scupper-holes each side amidships. They lead the water into the bilges, where the pumps can reach it."

"I found up there," continued the doctor, "a large piece of wood, badly charred by acid for half its length, charred to a lesser degree for the rest. It was oval in cross section, and the largest end was charred most."

"Scupper plug. I suppose they plugged the 'tweendeck scuppers to keep any water they might ship out of the bilges and away from the lime."

"Yes, and those plugs remained in place for days, if not weeks or months, after the carboys burst, as indicated by the greater charring of the larger end of the plug. I burrowed under the debris, and found the hole which that plug fitted. It was worked loose, or knocked out of the hole by some internal movement of the broken carboys, perhaps. At any rate, it came out, after remaining in place long enough for the acids to become thoroughly mixed and for the hull to cool down. She was in the ice, remember. Boston, the mixed acid went down that hole, or others like it. Where is it now?" "I suppose," said Boston, thoughtfully, "that it soaked up into the hold, through the skin."

"Exactly. The skin is calked with oakum, is it not?" Boston nodded.

"That oakum would contract with the charring action, as did the oakum in the hatch, and every drop of

that acid-ten thousand gallons, as I have figured-has filtered up into the hold, with the exception of what remained between the frames under the skin. Have you ever studied organic chemistry?"

"Slightly."

When tallow is saponi

"Then you can follow me. fied there is formed, from the palmitin, stearin, and olein contained, with the cauticizing agent-in this case, lime a soap. But there are two ends to every equation, and at the bottom of this immense soap vat, held in so lution by the water, which would afterwards be taken up by the surplus lime, was the other end of this equation; and as the yield from tallow of this other product is about thirty per cent., and as we start with eight thousand fifty-pound kids-four hundred thousand poundsall of which has disappeared, we know that, sticking to the skin and sides of the barrels down here, is-or was once one hundred and twenty thousand pounds, or sixty tons, of the other end of the equation-glycerine!" "Do you mean, Doc," asked Boston, with a startled look, "that"

"I mean," said the doctor, emphatically, "that the first thing the acids-mixed in the 'tween-deck to just about the right proportions, mind you-would attack, on oozing through the skin, would be this glycerine; and the certain product of this union under intense coldthis hull was frozen in the ice, remember-would be nitro-glycerine; and, as the yield of the explosive is two hundred and twenty per cent. of the glycerine, we can be morally sure that in the bottom of this hold, each minute globule of it held firmly in a hard matrix of sulphate or nitrate of calcium-which would be formed next when the acids met the hydrates and carbonates. of lime is over one hundred and thirty tons of nitroglycerine, all the more explosive from not being washed

of free acids. thing else."

Come up on deck.

Come up on deck. I'll show you some

Limp and nerveless, Boston followed the doctor. This question was beyond his seamanship.

The doctor brought the yellow substance-now well dried. "I found plenty of this in the 'tween-deck," he said; "and I should judge they used it to pack between the carboy boxes. It was once cotton-batting. It is now, since I have washed it, a very good sample of gun-cotton. Get me a hammer-crowbar-something hard."

Boston brought a marline-spike from the locker, and the doctor, tearing off a small piece of the substance and placing it on the iron barrel of a gipsy-winch, gave it a hard blow with the marline spike, which was nearly torn from his hand by the explosion that followed.

"We have in the 'tween-deck," said the doctor, as he turned, "about twice as many pounds of this stuff as they used to pack the carboys with; and, like the nitro-glycerine, is the more easily exploded from the impurities and free acids. I washed this for safe handling. Boston, we are adrift on a floating bomb that would pulverize the rock of Gibraltar!"

"But, doctor," asked Boston, as he leaned against the rail for support, "wouldn't there be evolution of heat from the action of the acids on the lime-enough to explode the nitro-glycerine just formed?"

"The best proof that it did not explode is the fact that this hull still floats. The action was too slow, and it was very cold down there. But I can't yet account for the acids left in the bilges. What have they been doing all these fifty years?"

Boston found a sounding-rod in the locker, which he scraped bright with his knife, then, unlaying a strand of the rope for a line, sounded the pump-well. The

rod came up dry, but with a slight discoloration on the lower end, which Boston showed to the doctor.

"The acids have expended themselves on the iron frames and plates. How thick are they?"

"Plates, about five-eighths of an inch; frames, like railroad iron."

"This hull is a shell! We won't get much salvage. Get up some kind of distress signal, Boston." Somehow the doctor was now the master-spirit.

A flag was nailed to the mast, union down, to be blown to pieces with the first breeze; then another, and another, until the flag locker was exhausted. Next they hung out, piece after piece, all they could spare of the rotten bedding, until that too was exhausted. Then they found, in a locker of their boat, a flag of Free Cuba, which they decided not to waste, but to hang out only when a sail appeared.

But no sail appeared, and the craft, buffeted by gales and seas, drifted eastward, while the days became weeks, and the weeks became months. Twice she entered the Sargasso Sea-the graveyard of derelicts-to be blown out by friendly gales and resume her travels. Оссаsional rains replenished the stock of fresh water, but the food they found at first, with the exception of some cans of fruit, was all that came to light; for the salt meat was leathery, and crumbled to a salty dust on exposure to the air. After a while their stomachs revolted at the diet of cold soup, and they ate only when hunger compelled them.

At first they had stood watch-and-watch, but the lonely horror of the long night vigils in the constant apprehension of instant death had affected them alike, and they gave it up, sleeping and watching together. They had taken care of their boat and provisioned it, ready to lower and pull into the track of any craft that might

approach. But it was four months from the beginning of this strange voyage when the two men, gaunt and hungry-with ruined digestions and shattered nerves— saw, with joy which may be imagined, the first land and the first sail that gladdened their eyes after the storm in the Florida Channel.

A fierce gale from the southwest had been driving them, broadside on, in the trough of the sea, for the whole of the preceding day and night; and the land they now saw appeared to them a dark, ragged line of blue, early in the morning. Boston could only surmise that it was the coast of Portugal or Spain. The sailwhich lay between them and the land, about three miles to leeward-proved to be the try-sail of a black craft, hove-to, with bows nearly towards them.

Boston climbed the foremast with their only flag and secured it; then, from the high poop-deck, they watched the other craft, plunging and wallowing in the immense Atlantic combers, often raising her forefoot into plain view, again descending with a dive that hid the whole forward half in a white cloud of spume.

"If she was a steamer I'd call her a cruiser," said Boston; "one of England's black ones, with a stormsail on her military mainmast. She has a ram bow, and -yes, sponsors and guns. That's what she is, with her funnels and bridge carried away.'

"Isn't she right in our track, Boston?" asked the doctor, excitedly. "Hadn't she better get out of our way?"

"She's got steam up-a full head; see the escape-jet? She isn't helpless. If she don't launch a boat, we'll take to ours and board her."

The distance lessened rapidly-the cruiser plunging up and down in the same spot, the derelict heaving to leeward in great, swinging leaps, as the successive seas caught her, each one leaving her half a length farther