Nov, 25, 1875] 



NATURE 



71 



species of Hyalomma, which occurred in considerable 

 numbers and in an excellent state of preservation. The 

 form of the sponge-body is almost spherical, with a com- 

 paratively small oscular opening, and the coil is much 

 shorter than in H. Sieboldi, in the largest specimens not 

 more than six inches in length. One remarkable point 

 was, that in no case was there a commensal Palython con- 

 nected with this sponge ; the coil was always perfectly 

 clean. The spicules of the network and of the sarcode 

 closely resemble those of the Japanese species, but they 

 all present marked specific differences in detail of form. 



On the 1 2 th of July the trawl was lowered at a depth of 

 2,740 fathoms. The net contained very few animals, 

 and was greatly torn and frayed ; but in a kind of packet 

 formed by an accidental folding of the net, there were 

 about a hundredweight of black mammillated concre- 

 tions, which, when they were poured out on the deck, had 

 very much the appearance of potatoes. The external 

 surface of the concretion was slightly rough, and a num- 

 ber of small animal forms, particularly a minute rhizopod 

 in a membranous tube, nestled in the crevices. The 

 nature of these concretions will be discussed hereafter. 



.On the 14th of July we reached the point lat. 38° 9' N., 

 long. 156° 25' W., whence we turned southwards towards 

 the Sandwich Islands. For the last few stations the tem- 

 perature of the water had been gradually sinking, and the 

 influence of the Japan current dying out ; the isotherm 

 of 10° C. was now only 100 fathoms below the surface. 



On the 17th of July we sounded in 3,025 fathoms, the 

 bottom still " red clay ; '"' and on the 19th in 2,850 fathoms. 

 A serial sounding taken at the latter station to 1,500 

 fathoms showed a considerable rise in the temperatures 

 near the surface, the isotherm of 10° C. having again sunk 

 to a depth of 200 fathoms, and that of 1 5° C. correspond- 

 ing with the ICG-fathom line. 



On the 24th, in 2,775 fathoms, the Albatrosses which 

 had followed the ship, to the number of from fourteen to 

 twenty daily since we left Japan, left us. In the evening 

 of the 27th, the Challenger anchored in the harbour of 

 Honolulu, 



This cruise naturally divides itself into two parts : a 

 section about 3,170 nautical miles in length, including the 

 stations from No. 237 to No. 253, very slightly to the 

 northward of east, between the parallels of 35° and 38^ N. 

 lat. ; and a meridional section of 1,128 nautical miles, 

 along the meridian of 155° W. long. The first of these 

 sections corresponds very closely in relative position with 

 the section in the Atlantic between Sandy Hook and the 

 Acores, and the points of resemblance and difference 

 between them, when fully worked out, must prove most 

 instructive. The two sections cross the two great deflec- 

 tions to the northward of the equatorial current, in the 

 Atlantic the Gulf-stream, and in the Pacific the " Kuro 

 Siwa ; " and the thermic influence of the two currents is 

 fairly contrasted. The influence of the Gulf-stream, if 

 not absolutely greater (and this is a point which it will be 

 somewhat difficult to determine), is at all events much 

 more concentrated and effective, owing to the continuity 

 of the coast-line of the American continent, to the way in 

 which the water of the equatorial current is driven into 

 the Gulf of Mexico and superheated there, afterwards to 

 be kept together and ejected in a defined stream through 

 the Strait of Florida, and to the absence of periodical 

 winds in the Atlantic. In the Pacific, on the other hand, 

 the main flow of the equatorial current is weakened among 

 the passages of the Malayan Archipelago ; and although 

 a large part of it is directed northwards by the broken 

 barrier formed by the Fiji Islands, the New Hebrides, 

 and Papua, it almost at once enters the region of the 

 Monsoons, where it is thwarted for half the year ; and it 

 can only be regarded as comparable with that portion of 

 the reflux of the Atlantic equatorial current which passes 

 outside the West Indian Islands. It passes the south 

 coast of Japan nevertheless as a very palpable and appa- 



rently a permanent current, exercising a very perceptible 

 thermic influence to a depth of at least 300 fathoms. 



In traversing the Pacific the influence of the Japan 

 current appears to be gradually lost, while I am still in- 

 clined to believe that in the Atlantic the Gulf-stream is 

 banked down against, and reflected from the western 

 coast of Europe. It is a question of great complexity ; 

 but it seems to me that it is consistent with our expe- 

 rience that the temperature of the water of the ocean at 

 any one place is due in a great measure to the tempera- 

 ture of the source of that water — not entirely due, for in 

 passing through a long distance the temperature of even 

 the greatest masses of water is certainly gradually altered 

 by conduction and mixture. 



The suggestions of Dr. Carpenter and Mr. Buchanan 

 that the existence of a deep layer of warm water in the 

 Atlantic might be connected in some way with the mean 

 annual temperature of the area, and the absence of ocean- 

 currents, are very suggestive ; and I looked forward with 

 great interest to an opportunity of testing them in the 

 corresponding position in the Pacific. But there seems 

 to be no trace of anything of the kind ; as the influence 

 of the equatorial reflux becomes weaker the temperatures 

 fall uniformly. 



To show that the conditions in the two oceans differ 

 more in degree than in kind, I give in Plates I. and II. 

 curves constructed from serial soundings along nearly 

 corresponding lines in the Atlantic and Pacific. Curves 

 A and B are added on Plate I. to show the position of the 

 deeper belt of abnormally warm wacer, which makes its 

 appearance near the coast of Europe. 



Plate I. 



North Atlantic Ocean. 



There seems to be little doubt that the enormous mass 

 of cold water which fills up the trough of the Pacific is 

 like the cold bottom-water of the Atlantic, an indraught 

 from the Southern Sea. The more the question is inves- 

 tigated the less evidence there seems to me to be of any 

 general ocean circulation depending upon differences of 

 specific gravity. It seems certain that both in the Atlantic 

 and in the Pacific the bottom-water is constantly moving 

 northwards ; and I am now very much inclined to refer 

 this movement to an excess of precipitation over the 

 water-hemisphere, a portion of the vapour formed in the 

 northern hemisphere being carried southwards and pre- 

 cipitated in the vast southern area of low barometric 

 pressure. I hope to enter fully into the discussion of this 

 matter on a future occasion. The temperature of the 

 water is greatly lower in the Pacific for the first thousand 

 fathoms than in the Atlantic in the corresponding latitude 

 of 35° N. There is one very remarkable difference between 



