CLYDE SEA AREA. 25 



between Loch Torridon and Stornoway gave 53°'3 for the surface, and 47°'8 at 85 

 fathoms. Thus although in that channel there are strong tidal currents, the typical 

 mixing of the whole mass of the water found in the North Channel did not occur. 

 This work was fully reported on in the Sixth Annual Report of the Fishery Board for 

 Scotland for the year 1887, Appendix C, and a summary of the conclusions was 

 published, under the title " Sea-Temperatures on the Continental Shelf," in the Scottish 

 Geographical Magazine, iv. (1885) 544-549. 



Trip XII., August 1887. — During the month of August 1887, Dr Murray made a 

 series of temperature soundings in the Clyde Sea Area, from the 6th to the 9th, doing all 

 parts except Loch Fyne, and from the 12th to the 17th, completing Loch Fyne 

 and the Arran Basin. Viewed as one trip, this would give an interval of 35 days since 

 the last. 



The air-temperature for August was the average for that month, and thus showed a con- 

 siderable falling off from July. The 6th was calm ; on the afternoon of the 7th a westerly 

 gale sprang up, shifting to north-west and blowing strongly on the 8th, and to north- 

 east, dying away on the 9th. For the rest of the time the wind was light and variable. 

 Rapid warming had taken place in the shallow lochs and estuary, and in every part of the 

 Area the water-temperature was 4° or 5° higher than in August 1886. The Channel was 

 occupied by a homothermic mass of water at 55°'3. At the same date my observations 

 on H.M.S. "Jackal " showed that in the open Atlantic west of St Kilda the surface tempera- 

 ture was 57°, at 30 fathoms 55°'l, and at 100 fathoms 48°. On that occasion I found 

 that the water of the North Atlantic was, speaking roughly, of uniform salinity, but that 

 it consisted of three horizontal layers of different temperature. The first was a 

 homothermic layer at 56°, extending from the surface to 25 fathoms ; this was succeeded 

 by a zone of rapid change of temperature about 15 fathoms thick, under which there 

 was a homothermic mass of at least 60 fathoms of water at a temperature between 48° 

 and 49°. It may not be too much to suppose that this superficial mass of warm water 

 represents the Gulf Stream drift ; at anyrate, it is certainly the warm surface water driven 

 in toward the land by prevailing westerly wind ; and as the upper homothermic zone 

 deepens toward shore, and is stirred throughout its whole extent in passing through tide- 

 ways, it appears that the North Channel is usually fed with surface water of the ocean, a 

 fact which would largely serve to account for its being warmer than the Clyde Sea Area, 

 even in summer. 



On this occasion the warm water pouring across the Great Plateau was obviously at 

 work warming the deep basins, the coldest parts of which lay at their upper ends. The 

 Dunoon Basin showed a patch of central heating separating cooler water which lay to the 

 north and to the south. This effect is probably accounted for by the current of warm 

 water sweeping in at right angles from the estuary. The coldest regions were naturally 

 the deep lochs : the bottom temperature of Loch Fyne was 45° "2, with no trace of the 

 intermediate minimum which kept the bottom water from rising above 44° '2 a year before ; 

 that in Loch Goil was 45°"4, contrasting with 43°'l in the previous August. 



VOL. XXXVIII. PART I, (NO. I). D 



