becomes more and more laborious. Dredging in 150 fathoms is very hard
work, if it has to be carried on by manual labour; but by the use of the
donkey-engine to supply power,[2] and of the contrivances known as
"accumulators," to diminish the risk of snapping the dredge rope by the
rolling and pitching of the vessel, the dredge has been worked deeper and
deeper, until at last, on the 22nd of July, 1869, H.M.S. _Porcupine_
being in the Bay of Biscay, Captain Calver, her commander, performed the
unprecedented feat of dredging in 2,435 fathoms, or 14,610 feet, a depth
nearly equal to the height of Mont Blanc. The dredge "was rapidly hauled
on deck at one o'clock in the morning of the 23rd, after an absence of
7-1/4 hours, and a journey of upwards of eight statute miles," with a
hundred weight and a half of solid contents.

[Footnote 2: The emotional side of the scientific nature has its
singularities. Many persons will call to mind a certain philosopher's
tenderness over his watch--"the little creature"--which was so singularly
lost and found again. But Dr. Wyville Thomson surpasses the owner of the
watch in his loving-kindness towards a donkey-engine. "This little engine
was the comfort of our lives. Once or twice it was overstrained, and then
we pitied the willing little thing, panting like an overtaxed horse."]

The trawl is a sort of net for catching those fish which habitually live
at the bottom of the sea, such as soles, plaice, turbot, and gurnett. The
mouth of the net may be thirty or forty feet wide, and one edge of its
mouth is fastened to a beam of wood of the same length. The two ends of
the beam are supported by curved pieces of iron, which raise the beam and
the edge of the net which is fastened to it, for a short distance, while
the other edge of the mouth of the net trails upon the ground. The closed
end of the net has the form of a great pouch; and, as the beam is dragged
along, the fish, roused from the bottom by the sweeping of the net,