NATURE 



405 



THURSDAY, SEPTEMBER, 2, 18S0 



THE CRUISE OF THE "KNIGHT ERRANT" 



IT was accepted by us as one of the general conclusions 

 from the temperature observations made on board 

 the Challenger that the normal vertical arrangement of 

 temperature in the ocean is somewhat in this wise. The 

 water is warmest at the surface ; from the surface it cools 

 rapidly for the first hundred fathoms or so ; it then cools 

 more slowly down to five or six hundred fathoms ; and 

 then extremely slowly to the bottom, where the minimum 

 temperature is reached. 



I need not here enter into detail as to the causes of this 

 nonnal condition, which have already been fully discussed.^ 

 i may state however, generally, that the temperature of 

 the upper strata is raised by solar radiation, and its dis- 

 tribution is affected by currents and by many other local 

 causes ; and that the water which has been cooled down 

 in the polar seas until it has acquired a high specific 

 gravity, flows along the bottom and into the deepest 

 abysses to which it has access. 



This normal vertical distribution of temperature is by 

 no means universal or even general; it exists only in 

 those parts of the ocean which are continuous throughout 

 their entire depth with a polar sea. No ocean is thus 

 continuous with the Arctic Sea ; a wide belt appa- 

 rently under these normal temperature conditions sur- 

 rounds the South Pole or the south polar land nearly 

 if not entirely, but the gulf-like northward extensions 

 of the water-hemisphere, the Atlantic and the Pacific, 

 show a distribution of temperature to a certain extent 

 abnormal, and in some seas which occupy more re- 

 stricted areas, the deviation from the normal conditions 

 is excessive. In oceans where the thermometer sinks 

 steadily from the surface to the bottom, that is to say, 

 in those under normal conditions, the bottom tempera- 

 ture at anywhere near 2,500 fathoms is a little below 

 the freezing point. The Atlantic Ocean is divided into 

 three areas ; in one of these, an area extending from the 

 Antarctic Sea along the coast of South America to ten 

 degrees or so north of the Equator, the temperature sinks 

 at the usual rate to 3i°'5 F. at the bottom (2,900 fathoms). 

 In another, the eastern basin, extending along the coasts 

 of Europe and Africa, the temperature sinks steadily to 

 35°'5 at a depth of about 2,000 fathoms, and this tempera- 

 ture extends to the bottom (3,150 fathoms) ; in the third 

 area, the western basin, off the West Indies and the coast 

 of North America, the temperature falls to 35^ at 2,000 

 fathoms, and this temperature is again continuous to the 

 bottom (3,475 fathoms). As extreme instances of this 

 abnormal condition, in the Celebes Sea, which attains a 

 depth of 2,600 fathoms, the minimum temperature — 3S°'5 

 F. — is reached between 700 and Soo fathoms ; the Banda 

 Sea, with a depth of 2,800 fathoms, reaches its minimum 

 temperature of 37° F. at 900 fathoms ; and the Sulu Sea, 

 which is at least 2,550 fathoms deep, has a uniform tem- 

 perature of so^'j F. from a depth of 400 fathoms to the 

 bottom. 



' " Hydrcgraphic Proceedings of the Voyage of Yl.^l.S. ChaUengcr." 

 Report on Temperatures by Staff-Commander 1 izard. R.N. (London, 1S76) ■ 

 ■• The Ailant.c," by Sir C. Wyville Thomson, F.R.S., vol. ii. p. 300, ct scq. 

 (London : Macmillan and Co., 1S77.) 



Vol. x.xii. — No. 566 



The combined results of our soundings and serial tem- 

 perature determinations led us to conclude that those 

 ocean basins in which the water is of a uniform tempera- 

 ture from a certain depth to the bottom are inclosed 

 within a continuous barrier of a height corresponding to 

 the depth at which the fall in temperature ceases ; and 

 that consequently no water at a temperature lower than 

 the isotherm of that depth can pass into them. Suppose 

 such a barrier to rise, as it does rise, in the Atlantic 

 between the south-western and the eastern basins to a 

 height of 2,000 fathoms below the surface, a sounding on 

 the west side to the depth of 2,500 fathoms close to the 

 barrier would give a temperature a little below 32° F., 

 while the thermometer at the same depth on the other 

 side of the barrier would register 35°'5 F. In this way 

 we may have very different temperatures at the same 

 depth, close to one another and apparently under abso- 

 lutely similar circumstances, and from our experience we 

 should be inclined to accept the existence of continuous 

 barriers as the almost universal explanation of such 

 phenomena. 



Cf course any generalisation such as I have indicated 

 partakes more or less of the character of a speculation. 

 It is impossible to trace out the entire line of the barrier 

 limiting an ocean basin and to prove its continuity. 



In discussing this matter during the cruise of the Chal- 

 lenger, Staff-Commander Tizard and I had often in our 

 minds the singular instance of contiguous areas of widely 

 different temperature conditions which had been examined 

 by Dr. Carpenter and myself in the Lightning and the 

 Poycupine in the years 1868 and 1869. 



In the channel between the north coast of Scotland and 

 the Shetland Islands, and the banks and islands of the 

 Faroe group, the average maximum depth is from 500 to 

 600 fathoms. An abrupt line of demarcation divides this 

 channel into two portions, one of which my colleague Dr. 

 Carpenter called the cold and the other the warm area.i 

 The temperature of the water to a depth of 200 fathoms 

 is much the same in the two areas ; in the cold area, 

 which occupies nearly the whole of the channel, extending 

 in a north-easterly direction from a line joining Cape 

 Wrath and the Faroe fishing banks, the temperature at 

 250 fathoms is 34' F., and 3o°-5 at the bottom (640 

 fathoms) ; in the ivarm area which stretches south-west- 

 wards from the same line, the thermometer registers 

 47° F. at 250 fathoms, and 42° F. at the bottom (600 

 fathoms). 



When the phenomenon was first observed, we concluded 

 than an indraught of cold water, passing southwards from 

 the Spitzbergen Sea, welled into the Faioe Channel, and 

 was met at its mouth and banked in by the north-easterly 

 extension of the Gulf Stream, forming along the line of 

 contact and partial mixture a "cold wall," comparable 

 with that described as occurring in the Strait of Florida 

 between the cold water of the Labrador Current and the 

 Gulf Stream near its origin. This view however pre- 

 sented many difficulties, and on reconsidering the matter 



I " Preliminary Report by Dr. W. B. Carpenter, V.P.R.S., of Dredging 

 Operations in the Seas to the North of the Britisli Islands, carried on in 

 H.M. steam-vessel Lightning " hy l)r. Carpenter and Dr. Wyville Thomson. 

 Professor of Natural History in Queen's College, Belfast \Proccedings of 

 the Royal Society of London, vol. xvii.). "Preliminary K'^port of the 

 Scientific Exploration of the Deep Sea in H.M. Surveying-vessel Porcupine 

 during the Summer of 1869. conducted by Dr. Carpenter, V.P.R.S., Mr. J. 

 Givyn Jeffreys, F.R.S., and Prof. WyviUe Thomson. LL.D., F.R.S. (Pro- 

 ceedings of the Royal Society of London, vol. xviii.) 



