n top
are from tallow-kids. The heat generated by the slaking lime set fire
to the barrels in contact, which in turn set fire to others, and they
burned until the air was exhausted, and then went out. See, they are
but partly consumed. There was intense heat in this hold, and
expansion of the water in all the tanks. Are tanks at sea filled to
the top?"

"Chock full, and a cap screwed down on the upper end of the pipes."

"As I thought. The expanding water burst every tank in the hold, and
the cargo was deluged with water, which attacked every lime barrel in
the bottom layer, at least. Result--the bursting of those barrels from
the ebullition of slaking lime, the melting of the tallow--which could
not burn long in the closed-up-space--and the mixing of it in the
interstices of the lime barrels with water and lime--a boiling hot
mess. What happens under such conditions?"

"Give it up," said Boston, laconically.

"Lime soap is formed, which rises, and the water beneath is in time all
taken up by the lime."

"But what of it?" interrupted the other.

"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 'tween-deck 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 a