March 23, 1871 | 
NATURE 

REPORT ON DEEP-SEA RESEARCHES 
Carried on during the months of Fuly, August, and September, 
1870, i LM. Surveying Ship ‘* Porcupine.” * 
By W. B. Carrenrer, M.D., F.R.S., AND J. Gwyn 
JEFFREYS, F.R.S, 
(Continued from p. 334.) 
DIRECTING our course again towards the Algerine coast, 
we kept nearly parallel to it during the greater part of the 
next day, occasionally sweeping the bottom with the ‘‘ tangles,” 
which gave us abundance of Polyzoa, Echinoderms, &c., of well- 
known types, without any specimens of novel or peculiar interest. 
We reached Algiers on the afternoon of the 26th ; and as it was 
necessary to take in coal, we remained in harbour until the 29th, 
when we resumed our easterly course, still keeping near the coast. 
The weather now began to be oppressively hot; the surface- 
temperature of the sea rising to 76° or 78°, and that of the air 
being often several degrees higher. Wishing to see what would 
be the point at which the effect of this extreme superheating 
would cease to manifest itself, we took a set of serial soundings 
at Station 53, with the following result, which we incline to 
consider typical of the condition of the proper surface-water of 
the Mediterranean in the summer season :— 
Sunhacemeemacd emery N77 
BebathOmSm als 2 70 
10 53 Go Ae Se mie 87,9 < 
20 5 eaten OL. 
30 a eet tn a2) 00) 
40 a oma eMerst ete 27-55 
50 ” CBepyitwa2 567 
100 an ae steas 555 
Thus the amount of heat lost in the first 20 fathoms is no less 
than 15°°5 ; and as much as 9°°5 of this loss shows itself between 
10 and 20 fathoms. 
Again proceeding into deep water, we perseveringly explored 
the bottom with the dredge ; and from a bottom of 1,508 fathoms 
we brought up some hundredweights of the same barren mud as 
had previously given so much trouble to so little profit. The 
sieve and the washing-tub again returned for answer “barren all,” 
Disappointing as this negative result was to us as zoologists, 
there are aspects under which it may be viewed that may give it 
no small value to geologists. On these, however, we can more 
fittingly enlarge hereafter. Once more, shifting our ground a 
few miles, we put down our dredge in 1,456 fathoms, and brought 
it up loaded with a similar profitless freight. 
We now determined to keep closer to the shore, and worked 
for several days along the African coast, for the most part using 
the “tangles,” the ground being too rocky for the dredge. Here 
we came upon a small fleet of coral fishers, and were not a little 
interested in finding that they employed ‘‘tangles” similar to 
our own as their most effective method of collecting. We swept 
the shore with these very assiduously, usually between 50 and 100 
fathoms; and although we obtained Polyzoa, Echinoderms, and 
corals in considerable abundance, there were not many of special 
interest. We may note, however, that several of the Polyzoa 
which occurred in the region in which the red coral is found had, 
when fresh, a red colour nearly as brilliant as that by which it is 
characterised ; but this colour, in the Polyzoa, was quite evan- 
escent. 
The extreme heat of the weather having produced an ex- 
hausting effect upon our crew, especially on the engineers and 
stokers, Capt. Calver considered it desirable to give them rest ; 
and we accordingly made for the Bay of Tunis, which we reached 
at mid-day on Saturday, Sept. 3rd. The town itself is situated 
at the head of a shallow lagoon, or salt-lake, that communicates 
with the sea by a narrow channel, and at this entrance there is a 
small sea-port named the Goletta, having a basin for vessels of 
moderate size. The lake, although about six miles long, has 
only from six to seven feet of water at its deepest part ; and when 
the water is unusually low, a small steamer, which plies between 
the Goletta and Tunis, is not always able to run, as happened at 
the time of our visit. Owing to the great evaporation, and the ab- 
sence of any stream of fresh water, the water of this lakeis usually 
very salt; but when heavy rains fall the level is considerably 
raised, and the saltness is diminished. Thus the condition of 
this lake in regard to that of the sea outside is sometimes that of 
* Extracted from the Proccedings of the Royal Society. 


415 
the Mediterranean in regard to that of the Atlantic, and some- 
times that of the Baltic towards the German Ocean ; and we 
would suggest whether it might not be possible, through our 
Consulate (which has an office at the Goletta), to have a reguar 
series of observations made upon the relative densities of the 
water of the lake and that of the sea, and upon the direction of 
the upper and under current in the channel of communication 
between them, that might furnish valuable data for the complete 
elucidation of the subject of currents occasioned by excess of 
evaporation. We availed ourselves of this short rest to visit the 
town of Tunis, which, for the most part, retains its genuine 
Moorish character ; and the ruins of Carthage, a few miles off, 
the most remarkable part of which consists of a series of immense 
reservoirs for water, supplied by an aqueduct that brought it 
from a range of mountains at no great distance, from which also 
the modern town of Tunis is supplied. ; 
This part of our work having brought us to the neigh- 
bourhood of the Island of Pantellaria, we landed on it with the 
view of visiting, if possible, a cavern which had the reputation of 
being ‘‘ of icy coldness.” As we found, however, that a whole 
day’s delay would be involved, we gave up the idea; and we 
afterwards obtained elsewhere the information we desired. The 
continuance of the very hot weather having brought a large part 
of our crew to a state of such exhaustion as to render a continu- 
ation of our operations undesirable, Captain Calver considered it 
expedient to proceed to Malta without further delay; and we 
anchored in the Harbour of Valetta on the morning of Saturday, 
September 10. Here we found it necessary to remain for ten 
days, the illness of our chief engineer, which we at first hoped 
might be only temporary, proving sufficiently serious to require 
that a substitute should be found for him. Our time was passed 
very pleasantly in visits to the various objects of interest in which 
the island abounds, and in the enjoyment of the kind hospitality 
of His Excellency the Governor, Vice-Admiral Key, and other 
officers. The time was too short for any careful examination of 
the geology of the island ; but one point which struck me as of 
special interest in relation to the deposit at present forming on 
the Mediterranean bottom will be specially noticed hereafter, 
Quitting Valetta Harbour at midday on September 20, we 
steered in a N.E. direction towards a point about sixty miles 
distant, at which a depth of 1,700 fathoms was marked on the 
chart. This we reached early the next morning (60); and a 
sounding being taken, 1,743 fathoms of line ran out. As this 
was the greatest depth we had anywhere met with in the 
Mediterranean, and as the basin in which the sounding was taken 
is cut off by the shallows between Sicily and Tunis from all but 
superficial communication with the western basin, we watched 
the heaving-in of the sounding apparatus and its accompaniments 
with no littleinterest. The thermometers recorded a temperature 
of 56°, which was one degree /zg/er than that which we had met 
with in our two deepest soundings (1,456 and 1,508 fathoms) in 
the western basin. The sample of the bottom brought up in the 
tube of the sounding apparatus indicated the prevalence of a 
yellowish clayey deposit so similar to that which had elsewhere 
proved so disappointing, that we could not feel justified in press- 
ing Capt. Calver for the sacrifice of nearly a whole day, which 
would have been required for a sinyle cast of the dredge at this 
depth. The specimen of bottom-water brought up by our water- 
bottle surprised us by its very small excess of density above the 
surface-water ; the specific gravity of the former being only 
10283, whilst that of the latter was 1°0281 ; and the proportion 
of chlorine per 1,000 being 21°08 in the former, whilst that of 
the latter was 20°77. The surface-water being here #ore dense 
than the average, the bottom-water was /ess dense; a result which 
a good deal surprised us at the time, but which subsequent com- 
parison with the densities of specimens taken from the greatest 
depths we had sounded in the western basin showed to be by no 
means exceptional. And when we came to reason out the mode 
in which surface-evaporation may be presumed to operate in 
augmenting the density of the water beneath, we found it to be 
quite in accordance with a friori probability, that the deepest 
water should show the Zeas¢ excess of density above the water at 
its surface. 
Having thus satisfied ourselves, so far as we could do 
by a single set of observations, that the physical conditions 
which we had found to prevail in the western basin of the 
Mediterranean present themselves also in the eastern, we 
steered for the coast of Sicily; and in a few hours came 
in sight of Syracuse, with the lofty mass of Etna asa mag- 
nificent background in the remote distance. The clouds which 
lay upon its summit during the earlier part of the day gradually 

