CLYDE SEA AREA. 93 



Section III., August 10th -11th, 1886. — The wind at the time of observation was 

 light, and blew up the loch. Since June the Arran Basin had heated up to 53°"5 on the 

 surface, and 45° on the bottom. The Minard Basin was filled with nearly uniformly 

 warm water. The isotherms cross it nearly horizontally clown to the level of the bars, 

 but below that level the Gortans Basin remains warmer than the water at the same 

 depth either outside or inside; e.g., at 30 fathoms it is 48° in Arran Basin, 48°"3 in 

 Gortans Basin, and 46° in the Upper Basin of Loch Fyne. 



At Otter the warm skin is broken by somewhat superficial upwelling. In the Upper 

 Basin below 45-50 fathoms the temperature is the same as in June. The cold mass is 

 much reduced in size, and the area under 44° is now only 20 fathoms thick at Inveraray, 

 its maximum. Its minimum temperature is 43° "3 (?), and the line of minimum has sunk 

 to 35 fathoms. The cold mass is in contact with the landward end of the loch, but does 

 not reach so far as Furnace. This cold sheet has effectually prevented the penetration 

 of heat to the water below. 



The upper isotherms below 10 fathoms show a strong down-loch dip, which is due, 

 probably, not to shearing motion set up by wind, but to actual heating by the overflow 

 of dense warm water from the Gortans Basin. That this is a very important factor is 

 proved by density observations. From Furnace to Cuill, at about 5 fathoms, a number 

 of isotherms run very close to each other, showing a thin layer of hot water resting 

 abruptly upon the slowly warming, cooler layer below. 



Section IV., 27th-2Sth September 1886. — The superficial layer of 20 fathoms ranges 

 from 51° to 52 0, 5, the mass approaching to homothermic conditions, and entirely filling 

 the Gortans Basin, where the minimum on the bottom is 50° '7. Outside, at the same 

 depth, it is 50°, and at the bottom over 47°. Inside it is 46°. There is a very slight 

 rise of the isotherms at Otter. 



In the Upper Basin the non-conducting pad of cold water has been practically 

 warmed away ; but the minimum temperature, still over 44°, docs not yet quite reach 

 the bottom, so that the fall of temperature is not quite uniform from the surface. The 

 isotherms, on the whole, are slightly curved, following the contour of the bottom, and 

 between 50° and 47°, about 30 fathoms, they are most crowded, showing a great mass of 

 warm water passing rapidly into a great mass of cold water. The position of this 

 Sprungschicht, as it has been termed in German, is very characteristic just below the 

 lip of the Minard barrier, suggesting that the inflow of warm water from the Gortans 

 Basin spreads over but does not sink through the cold mass filling the Upper Basin. 



Section V., 16th-17th November 1886. — In this section cooling from the surface has 

 set in strongly, and the isotherms show some very interesting relations. Outside, the 

 temperature rises to 51°, about 15 fathoms, and remains practically constant, the water 

 growing somewhat warmer toward the bottom. The Gortans Basin is filled with water 

 of the same temperature, the isotherm of 50° falling to the Minard barrier. Inside, the 

 surface temperature falls toward the head of the loch, but the water grows warmer from 

 the surface to about 15 fathoms, where the maximum (about 50°) occurs, and then cools 



