DESCRIPTION OF THE EXPEDITION. 15 
the wire thoroughly taut we used an 80-Ib. lead at the tail and hauled in by the winch 
over a specially made 3-fathom Lucas block attached to the steamboat’s after-davit 
swung outwards. The water-bottles employed were of the reversing type, as recom- 
mended to us by Mr. D. Matthews and used by the International Bureau, fitted some 
for messengers and others with propellers. Attached to each were frames for two 
reversing thermometers. ‘To store the water for analysis from the above, and also from 
our daily samples, we used specially blown bottles of green insoluble glass with china 
patent clip stoppers and rubber rings. They were fitted into felt-lined cases properly 
partitioned up, each containing 42 bottles and their requisite printed labels. 
In dredging we used a steel rope, 1 inch circumference, 114 strands in six cords, 
a pattern regularly made by Messrs. Bullivant & Co. The breaking-strain was supposed 
to be 43 tons, but, as tested by us, it proved well able to take any load up to 6 tons. 
It was placed beneath the bridge on its drum, which took 2000 fathoms (fig. 3). From 
there the rope was led through a block under the forecastle down the starboard side to 
the winch, around which three or four turns were taken, thence through a lead up to the 
measuring-block attached to the steamboat’s after-davit, the latter being especially guyed 
to the fore- and main-masts to stand the strain. Previous to leaving England we had 
obtained four spiral steel springs, each 15 inches long, with a total of 12 inches 
compression under a strain of 5 tons. We had intended to have a frame made for them 
in Ceylon, but, owing to a series of errors preventing our dredging-wire from reaching 
us before we got to Mauritius, we did not have them fitted up until we arrived at that 
island. As the distance from the top of the davit to the water was small, we placed 
only three in series in the accumulator, thus getting for a strain of 5 tons a compression 
of 9 inches, or 1°8 inches for lton. To hold the wire we used a hemp stopper, which on 
occasions of severe strain allowed the rope to pay out somewhat, and undoubtedly saved 
us on many occasions. On the whole these arrangements worked admirably, but the 
drum for the wire should be part of the winch, or itself be capable of being wound up 
by steam. Such an arrangement was impossible on the Sealark, so that four hands 
were commonly placed on the drum to wind up the rope, but the labour was very 
severe. The dredges should be heaved in fairly rapidly and without stopping (which is 
disastrous), or the greater part of the swimming and crawling forms may be lost. One 
of the causes of our failures in dredging in the Chagos was undoubtedly the absence of 
any accumulator to show us the strain. Subsequently, after some experience, we were 
enabled, by watching the contraction of the accumulator, to see whether the dredge or 
trawl was passing over the bottom properly. Further, we were enabled in some degree to 
estimate the character of the ground over which we were working. We could see when 
we were caught up, and so could stop the ship, and by going astern trip the net if 
necessary. The arrangement was awkward, in that the whole of the starboard gangway 
had to be kept clear in case of accidents. Few of our nets could be swung clear of the 
water, and the delay in vetting them on board by hand often caused us the loss of 
valuable specimens. In manceuvring tue ship during dredging our chief concern was 
to keep the wire rope clear of the ship and of her propeller. We would be inclined to 
recommend any future expedition to employ a boom from the mast, taking the strain 
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