APPARATUS EMPLOYED IN DEEP-SEA EXPLORATIONS. 287 
to I7cwt. a few minutes before the dredge-rope parted. This 
happened in comparatively shallow water, on a day when what 
a landsman would call half a gale of wind was blowing. 
The expedition was divided into three cruises ; the first, 
under the charge of Mr. J. Grwyn Jeffreys, F.R.S., and accom- 
panied by the writer, lasted from the end of May till the 
middle of July, and the area of its work lay between latitudes 
51° 20' N., and 57° 30' N. (Rockall), the westernmost point 
being 15° 30' W. The second, under the charge of Dr. 
Wyville Thomson, F.R.S., accompanied by Mr. John Hunter, 
M,A., of Belfast, lasted from the end of July to the middle of 
August, and was occupied in explorations off the S.W. of 
Ireland ; the deepest dredging of all, 2,435 fathoms, being 
accomplished at the most southerly point reached, 47° 35' N. 
and 12° 15' E. The third, under the charge of Dr. Carpenter, 
F.R.S., accompanied by Dr. Wyville Thomson and Mr. P. H. 
Carpenter, lasted from the middle of August to early in 
September, and was devoted to an examination of the “ warm 
and cold areas” between the Hebrides, Shetlands, and Faroes, 
the northern limit being Thorshaven, in the Faroes, the 
western 9° 20' W., and the eastern 0° 35' E. In this cruise the 
greatest depth attained was 750 fathoms, but during it a most 
important addition to the dredging apparatus was made by 
Capt. Calver. It consisted of horizontal arms attached to the 
dredge frame, to which were fastened two or three 66 swabs,” or 
“ hempen tangles ” as they were christened by their inventor, 
by which the bottom of the sea was swept as well as scraped. 
In this way many animals were captured which seldom or 
never were obtained in the dredge-bag, and the utility of this 
contrivance was so evident that no deep-sea dredge can hence- 
forth be considered complete without it. 
In order to dredge in any particular spot, it is necessary to 
know the exact depth of water. Sounding, therefore, is an 
essential preliminary to dredging. In the Porcupine’s sound- 
ings three objects were attained— (1) a knowledge of the 
exact depth, (2) the temperature at that depth, (3) a sample of 
water from the bottom. Where there was reason to believe 
that the depth was less than 1,000 fathoms, an ordinary “ deep- 
sea cup-lead,” weighing 1 cwt., was used ; in other cases the 
“ Hydra ” machine before described. The sinker or weight 
having been attached, two of the Miller-Casella thermometers 
were made fast to the line immediately above the weight, and 
close to them the water-bottle. The whole was then let go, 
the line running out with great rapidity, at the rate of 100 
fathoms per minute at first. By a seconds’ watch, the time of 
each 100 fathoms in running out was noticed, the interval in- 
creasing with the friction of the water on the greater length of 
