16 DR HUGH ROBERT MILL ON THE 



part of April. On this trip, indeed, the temperature at every part of the Area was lower 

 than on any subsequent occasion in the whole period during which observations were 

 carried on. Observations were made from the 13th to the 21st, omitting the 18th, and 

 the prevailing character of the whole region from the Channel to the loch-heads was 

 uniformity. The surface temperature indeed varied a few degrees, averaging about 44° *5 

 for all parts except the Channel and Loch Fyne (from Otter to Strachur), where it was 

 about 42° '5. The surface water formed a thin layer: at 15 fathoms the average 

 temperature was about 41° "5 for all parts except the Channel and Loch Fyne, where it 

 was about 42°, and this distribution held good to the bottom. Between 10 or 15 

 fathoms and the bottom there was not in any part a greater variation than o, 2. The 

 mass of the water in the Gareloch and Loch Long had the temperature 41°'8, which 

 may be taken as typical of the lochs and basins. Loch Fyne, however, had the mean 

 temperature of 42° *0, and so also had the Channel. This difference of temperature, 

 although small, is significant. It shows that the Area, as a whole, had cooled down more 

 than the open water of the Channel, influenced by the Gulf Stream, and more 

 than the doubly enclosed water of Loch Fyne, which had not lost the whole of its 

 previous summer's increment of heat. 



The prevailing winds for some time previously had been northerly and north- 

 easterly : the conditions during the trip were anticyclonic. The result was in almost 

 every case a down-loch wind, which was strongly felt in Loch Fyne and Loch Strivan. 

 The observations of density showed evidence of upwelling at the head of all the lochs, 

 and this was confirmed by the temperature sections for Loch Fyne and Gareloch, in 

 both of which the isotherms had a definite seaward dip, showing upwelling of cooler 

 water from below. 



The mean temperature of each sounding, the surface-temperature, and the tempera- 

 ture at 30 fathoms are shown on map 1 in Plate XXI. as a type of temperature 

 distribution at the spring minimum. 



During the trip there was a comparatively rapid heating of the water in progress, 

 observations on the Gareloch on the 13th and 21st showing a gain of from 2° to 3°. 



The seaward reaches of the Firth of Forth were practically at the same temperature, 

 averaging 41 0- 5, as ascertained by a trip from Granton to the Isle of May on April 23rd. 



Trip II, June 1886. — The central day of this trip was sixty-one days after the 

 central day of Trip I. In the interval the curve of air-temperature was parallel to the 

 long period mean, but at least l°-5 lower. The winds had been prevailingly northerly. 

 During the trip (June 16-22) the wind changed to north-west and west, and at times 

 blew strongly. There was bright sunshine most of the time, contrasting with the 

 weather of the previous six weeks, when there was a marked lack of sunshine. 



In Loch Goil and Loch Strivan there were strong down-loch winds during 

 observations; in Loch Fyne the wind was blowing freshly up the loch, and in 

 Loch Long and the Gareloch the wind was transverse, from the west. Eapid heating 

 had taken place everywhere on the surface, especially in the seaward division ; the 



