Sept. 2, 1880] 



NATURE 



407 



On August 10 the Knight EiTant -went out again and 

 got several fairly successful hauls of the trawl and a serial 

 temperature-sounding in the %uarm area, . returning on 

 Thursday the 12th, and she left Stornoway for the fourth 

 time on Monday, August 16, when the party landed on 

 Rona and gave it a cursory examination. They then 

 steamed towards the deep water of the cold area, and on 

 Tuesday the 17th they trawled successfully, and took a 

 serial temperature-sounding in 540 fathoms. They re- 

 turned to Stornoway for the last time on the evening of 

 Thursday, and left on the following day for Greenock, 

 where they arrived on Monday, the 23rd. 



The observations made by Capt. Tizard in the Knight 

 Erra/itha.ve fully corroborated the results olxhtLightin'ng 

 and Porcupine as to the facts of the abnormal distribution 

 of temperature in the Faroe Channel. They have also 

 established the existence of a submarine ridge rising to 

 within 300 fathoms of the surface, in the position in 

 which such a ridge is required to satisfy the conditions of 

 the doctrine of the interference of continuous barriers 

 with the distribution of deep-sea temperatures. Thus far 

 they may be regarded as entirely successful. 



The highest line of the ridge has probably not, been 

 found, and the details of temperature have yet to be 

 traced out more accurately along the line and for a short 

 distance on either side. I consider that it would be of 

 the greatest interest to work this case out fully as a 

 striking example, within a few miles of our own shore, 

 of a physical phenomenon of importance from its wide 

 occurrence. 



The Knight Errant was found quite unsuitable for 

 such work; a small steamer of ordinary strength, with 

 stowage for coals for a fortnight's steaming, and with 

 sails to enable her to lie to in a breeze, could do all that 

 is required within a month or six weeks of the ordinary 

 variable weather of these seas. 



Although the solution of this temperature problem was 

 the principal object of this summer's trip, I wished greatly 

 to make some additional observations on the nature of 

 the faunae on the two sides of the ridge, and I was espe- 

 cially anxious to procure some fresh specimens of sponges 

 as material for the structural part of the memoir in which 

 I am engaged with Prof. Franz Eilhart Schultze on the 

 Hexactinellidas of the Challenger Expedition. 



The Admiralty decUned to give us any material assis- 

 tance in this direction, but they allowed me to take the 

 gear on board and to get a cast of the trawl or dredge in 

 the intervals of sounding, or when the sounding work 

 was oyer. I accordingly provided 1,000 fathoms of 2^ 

 inch dredge-rope and other necessary appliances, and 

 Messrs. Henderson, ship-builders, Glasgow, kindly lent 

 us an excellent steam-winch, which was fitted on deck 

 and was of the greatest service both in sounding and 

 trawling. Owing to the boisterous weather and insuffi- 

 ciency of the vessel, this part of our undertaking was not 

 very successful. I got none of the coveted sponges, but 

 two or three hauls of the trawl were taken in each area, 

 and a number of highly-characteristic abyssal forms were 

 procured, including some deep-sea fishes, several crusta- 

 ceans, and a number of gigantic pycnogonids, some in- 

 teresting echinoderms, including Porocidaris, Aslheno- 

 soma, Phorinosoma, Poiirtalesia, Rhizocrinus, and others ; 

 some corals, and many curious rhizopods. As the vessel 



has not yet returned, I take these names from Mr. 

 Murray's rough notes. 



Enough has been done to give further evidence, if such 

 were needed, that a small district on the northern slope 

 of the coast of Scotland will afford a richer harvest to a 

 properly-organised dredging-excursion than perhaps any 

 other spot on the earth. The whole area is singularly 

 productive, and it is bisected by a narrow line, on the 

 one side of which the warm sea at a depth of 500 to 600 

 fathoms vies in abundance and variety of abyssal forms 

 with the favoured patches off Inosima and Zebu ; while 

 on the other side of the line, within a distance of a few 

 miles, we find an epitome of the fauna of the depths of 

 the Arctic Sea. C. Wyville Thomson 



LETTERS TO THE EDITOR 



\Thc Editor does not hold himself responsible fir opinions expressed 

 by his correspondents. Neither can he undertake to return, or 

 to correspond with the writers of, rejected mamiscripts. No 

 notice is taken of anonymous communications, 



[ The Editor urgently reqitests correspondents to keep their letters as 

 short as possible. The pressure on his space is so great that it 

 is impossible otherwise to ensure the appearance even of com~ 

 munications containing interesting and noz'cl facts. 1 



A Fragment of Primeval Europe 



The paper in Nature, vol. xxii. p. 400, by Prof. Archibald 

 Geikie, on the glacial phenomena of the north-west coast of 

 Scotland, contains on many points a most true and graphic 

 description of a most peculiar and a most interesting country. 

 But 1 demur to its accuracy on one of the main features to which 

 he refers. The amount of glaciation on the hills of Laurentian 

 gneiss, as represented in the sketch on p. 401, is inordinately 

 exaggerated. I know that country well, both in its general 

 aspect and in its details, and no part of it presents such a scene 

 of symmetrically rounded hills, like the huts of Caffres in Zulu- 

 land, as that depicted in the sketch. 



It is true that all the lower hills are more or less strongly 

 glaciated. But they are also full of low cliffs, and precipitous 

 rocks upon the sides of the glens, and the whole character of the 

 glaciation is such as to suggest the action of heavy floating ice 

 such as that of the " Palseocrystic Sea," and which acted only 

 upon surfaces specially exposed. 



Ben Stack, which is 2,364 feet high, and is composed of the 

 same rock, is not rounded at all, and on the north-west face is 

 full of great precipices along which no glaciation can be seen. 



It is perfectly true that the same glaciation which is common 

 on the exposed surfaces of the gneiss cannot be traced on the 

 Cambrian sandstones which overlie it. But tliis is probably due 

 to the obliteration of the ice-marks by subsequent atmospheric 

 action, which tells rapidly and powerfully on the sandstones, 

 whilst it is almost inoperative on the intensely hard and tough 

 Laurentian gneiss. 



That this is the true explanation of the difference now jire- 

 sented by the two rocks, is evident from the fact that the next 

 rock in the ascending series, namely, the white quartzites, do retain 

 surfaces in abundance which are splendidly glaciated. I know 

 no spot in Scotland where the polished surfaces due to glaciation 

 are seen on a greater scale than on the top of the white quartzites 

 \vhich cap the mountain of Queenaig in Assynt. This is a 

 classical area in geology — a sketch of it forming the frontispiece 

 of Murchison's "Siluria." The road from Inchnadamf to 

 Kylescue and Scourie passes over a plateau formed of this 

 quartzite, and the beds of white rock, highly glaciated, shine for 

 miles through the heather. 



Tlie glaciation which left these surfaces must have passed over 

 the sandstones also. But the rock was not of a material calcu- 

 lated to retain the marks. 



Nevertheless I am not pi-epared to deny that possibly the 

 gneiss of Sutherland may have been doubly glaciated — once in 

 the glacial epoch as hitherto known to geology, and also at some 

 former epoch inconceivably remote, when similar conditions 

 had prevailed. 



If well glaciated surfaces of the gneiss can be distinctly traced 



