APPARATUS EMPLOYED IN DEEP-SEA EXPLORATIONS. 285 
the frame was increased to about 2cwt. by the addition of 
plates of iron. The bag was double, the outer being a close 
net of sounding-line, the inner a piece of “ bread bag,” a some- 
what open canvas, and was so arranged as to be readily 
detached from the frame, and washed, to avoid the possibility 
of mixing the results of one dredging with another. The 
animals &c. brought up in the dredge were readily separated 
from the mass of ooze or mud in which they were embedded 
by a series of graduated sieves, placed one within another, the 
sieve of largest diameter and smallest mesh being at the 
bottom of the series. When the whole was agitated in a tub 
of water, the impalpable mud speedily passed through all the 
sieves, and the animals were deposited upon them according to 
their size. 
The dredge-rope was the best Chatham “ hawser-laid ” rope 
that could be made ; two sizes were employed — 2 inches and 
2J inches in circumference respectively. There was an admirable 
arrangement for stowing it on deck, by which its manipulation 
was rendered very easy, which is represented in the full-page 
plate. A number of pins, about 18 inches long, terminating 
in white balls, projected inwards from the bulwarks, and on 
these pins the rope was loosely coiled. In this way, 3,000 
fathoms of rope (nearly 3J- statute miles), weighing nearly 
tons, were placed within easy reach on the deck. 
In order to haul in the great lengths of sounding-line and 
dredge-rope, as well as the dredge with its contents, a small 
donkey-engine was provided and placed on deck between the 
paddle-boxes. The experience of the 1868 expedition, in 
H.M.S. Lightning , had shown that a double-cylinder engine 
was almost essential, so that by the alternate action of the two 
pistons the application of the power might be uninterrupted. 
The engine on board the Porcupine fully answered the expec- 
tations formed of it, and in almost every case, whether it was 
sounding-line from a moderate depth, or the dredge and its 
contents with 3,000 fathoms of rope attached, the hauling-in 
was performed at the rate of one foot per second, or 600 
fathoms per hour. Occasionally, in fine-weather soundings, a 
drum of greater speed was attached to the engine. 
A very important adjunct to the dredging and sounding 
apparatus remains to be described. It is figured in the follow- 
ing cut, and its position on board the vessel is clearly seen in 
the full-page plate. It was called the “ accumulator,” and the 
twofold object of the contrivance was — to indicate any sudden 
and undue strain upon the dredge-rope or sounding-line, and 
to relieve it in a measure — automatically, as it were. The 
dredging was carried on at both ends of the vessel, a similar 
contrivance to that seen in the stern being fixed near the bow. 
