NOTES ON DEEP SEA SOUNDINGS. 65 



on 21st May, 1839, the ship in which I arrived here was carried 

 46 miles to the south in twenty-four hours, about 25 miles from 

 the land, the depth at noon being 70 fathoms. 



On the" Challenger's" passage fromMelbourne to Sydney, while 

 the surface temperature rose to above 70° the cold understratum 

 rose nearer to the surface, the isotherm of 40° lying at about 400 

 fathoms, and the descent nearly uniform. But from Sydney to 

 Cook's Strait, in New Zealand, while the surface temperature fell 

 with increase of the distance from the Equator, the isotherm of 

 40° again deepened to more than 700 fathoms, the stratification 

 above being nearly uniform. On the way to Fiji, as the surface 

 temperature increased, the isotherm of 40° again rose to within 

 450 fathoms from the surface. Comparing these observations 

 with those recorded of the Equatorial Atlantic, to which Dr. 

 Carpenter had already drawn notice last year, in his paper headed 

 " Further Inquiries," he thinks " it may now be stated, ivith some 

 confidence, that the lightening of the upper stratum by elevation of 

 its temperature tends to favour the ascent of cold water from the 

 bottom, ivJiich is precisely what theory would lead us to anticipate." 



He further states that the soundings taken by the " Challenger" 

 in different parts of the Eastern Archipelago confirm this view, 

 and in illustration he quotes a passage which I have to-night 

 already referred to, from Captain Nares, relating to the shallow 

 bank of 1,300 fathoms, between Sandy Cape (Queensland), New 

 Caledonia, and New Guinea. He deals with the other cases I 

 have also quoted, and comes to the same general conclusion, con- 

 firmatory, as he believes, of his opinion that currents are due to 

 the interchange of temperatures. 



He argues, in dealing with the results of the observations made 

 on board the "Tuscarora," that if the action of the Gulf Stream in 

 the cut de sac of the northern Atlantic (that stream being a mere 

 rivulet) is capable of producing the downward displacement of 

 colder water (which Professor Wy ville Thomson suggests as a vera 

 causa*), "much more ought that effect to be produced in the North 

 Pacific by the Japan current, which has no outlet at all save the 

 narrow and shallow strait of Behring." But it may be mentioned 

 that the depth of Behring's Strait is only 32 fathoms ; and it 

 may be asked how could an Arctic current only 192 feet deep 

 affect the water in the enormous depression of the North Pacific, 



* It is well to mention that Professor Wyville Thomson, who was with Dr. 

 Carpenter in the first explorations of the Atlantic, holds views not in exact 

 agreement with those of his companion. These are deserving of full con- 

 sideration, and are freely stated in his work on the " Depths of the Sea," in 

 chapter viii of which work the Gulf Stream is freely discussed. See pp. 

 397-398. 



