4o6 



NATURE 



\Scpt. 2, i8So 



it now seemed certain that if our generalisation with 

 reo'ard to the cause of great differences in bottom tem- 

 peratures within short distances be correct, a submarine 

 ridge rising to within about 200 fathoms of the surface 

 must extend across the mouth of the channel between the 

 coast of Scotland and the Faroe banks. We recognised 

 this as a test case which we might probably be able to 

 examine thoroughly, as it was within our easy reach and 

 on a sufticiently small scale ; and I determined to take 

 the first opportunity of making a careful survey of the 

 channel with Capt. Tizard's co-operation, if possible 

 before the Challenger temperature results were finally 

 discussed. 



I was pre\ented by various circumstances from taking 

 any active steps in this direction until last year, when the 

 Hydrographer of the Admiralty kindly consented to 

 arrange another opportunity for sounding the Faroe 

 Channel. I was obliged again to postpone the under- 

 taking on account of a severe illness, and it was not until 

 the early part of the present summer that I felt well 

 enough to renew my application. I then wrote the 

 following letter to the Hydrographer : — 



" Sonsy lie, Linlithgoiu, June 16, 1880 

 '■ Dear Captain Evaxs, — As you are aware, during 

 our cruise in H.M.S. Lightning, in the year 1868, Dr. 

 Carpenter and 1 found to our surprise that the channel 

 between the Faroe Island and the coast of Scotland con- 

 sisted of two ver>' distinct ' areas,' the deep water in the 

 two divisions differing in temperature to a marked degree. 

 Consequent upon the difference of temperature, the fauna; 

 of the two areas w^ere also different. The 'warm' area 

 was separated from the ' cold ' by a distinct line of de- 

 marcation running apparently from about Cape Wrath 

 past the Island of Rona, and as far as the southern Faroe 

 fishing banks. During the voyage of the Challenger we 

 met on many occasions with an abrupt change in the 

 deeper temperatures along a definite line, and we arrived 

 at the general conclusion that the phenomenon depended 

 in all cases upon the interruption of the flow of an under- 

 current by a raised submarine ridge. The instance 

 between Scotland and Faroe still, however, remains the 

 most conspicuous as well as the most accessible, and it is 

 very important for us before concluding the Report of the 

 Challenger Expedition, to have an opportunity of checking 

 with our greatly increased knowledge our earlier observa- 

 tions. 



" I have carefully considered what would be the 

 minimum amount of work required for this purpose, and I 

 now write to ask if you could, with the sanction of their 

 Lordships, authorise Capt. Tizard, now surveying on the 

 west coast, to run north to Stornoway and sound out the 

 line indicated. This w'ould occupy a month, or perhaps 

 a little more. 



" As remarkable differences in the distribution of marine 

 animals accompany these differences in temperature, I 

 should greatly regret if we had not a few casts of the 

 trawl on each side of the line, but any additional expense 

 involved tor this purpose I will gladly meet. I regret 

 greatly that my present state of health prevents my com- 

 mitting myself to accompany tlie vessel during the whole 

 time, but I will be at Stornoway during the sur\'ey, and 

 my chief assistant, Mr. Murray, is prepared to go. I 

 should think that about the middle of July would be the 

 best time for the trip, if that time would be convenient. 

 Trusting for your assistance to the kind interest you have 

 always taken in our work, believe me ver>' truly yours, 

 " C. Wyville Thomson " 



1 give this letter in full to show that ovir anticipations 



were ver)- definite, although they were founded entirely 

 upon the comparison of serial temperature soundings. 



Their Lordships agreed to my proposal, and on July 

 22, 18S0, I joined the Knight Errant at Oban, and 

 proceeded to Gairloch, and thence to Stornoway, where 

 we arrived at mid-day on Saturday, the 24th. The weather 

 was delightful, and the Minch as smooth as glass ; when 

 we reached Stornoway, however, the barometer had begun 

 to fall, and continued sinking steadily with a rising breeze 

 from the north-east. After coaling on Monday forenoon, 

 the vessel left Stornoway Harbour at i p.m. with a rather 

 unfavourable weather forecast. I meant to have gone 

 with her on this trip but I was advised to give up the 

 idea, and the civilians who accompanied Capt. Tizard 

 were Mr. Murray, our indefatigable assistant Mr. Frederick 

 Pearcey, with my son as a supernumerary. Taking the 

 island of North Rona as a point of departure, during 

 Tuesday the 27th, and Wednesday the 2Sth, the Knight 

 Errant ran a sectional line of soundings, the distance 

 between the soundings averaging ten miles, between the 

 shallow water on the Scottish coast and the bank to the 

 south-west of the Faroe Islands. Fourteen soundings 

 on this line gave the following depths and bottom tem- 

 peratures : — 



The line was therefore entirely in the warm area, and no 

 perceptible amount of water from the cold area could be 

 shown to pass in this direction towards the Atlantic. 



Capt. Tizard then proceeded a little way to the north- 

 eastward, and commenced running a second line, parallel 

 to the first and about eight miles from it, back towards 

 the Scottish coast. Soundings were continued on the 

 second line at the same average distances as before on 

 Wednesday and Thursday morning, when, the barometer 

 falling rapidly and the sea running high with a gale 

 from the north-east, it was thought prudent to bear up 

 for Stornoway, which they reached on Friday after a 

 somewhat anxious twenty-four hours. 



On Tuesday, August 3, the weather looking somewhat 

 better, the Knight Errant left Stornoway and carried a sec- 

 tional line north-north-west from Rona towards the last 

 sounding; they completed the second line of soundings 

 on the evening of Wednesday, the 4th inst. On this line 

 twelve soundings g.ave depths and bottom temperatures 

 according to the following t.able : — 



.\11 these soundings therefore, with the exception of Nos. I, 

 2, and 3, which were across the ridge in the colil area, and 

 No. 9, which was in the deep water of the zoann area, 

 gave a depth of under 300 fathoms, and were consequently 

 on the ridge. 



