22 DR HUGH ROBERT MILL ON THE 



was neither so low nor so uniformly distributed as in April 1887. The surface water 

 had once more commenced to warm up, especially in the seaward portion, and there was 

 a slight fall of temperature toward the bottom. The mass of water in the Channel 

 averaged 44° '5 ; in Loch Goil and the Upper Basin of Loch Fyne it was warmer, cooling 

 having taken place very slowly. The Arran Basin had on the whole a temperature 

 under 43°'5, and the Dunoon Basin and shallow lochs were slightly colder than this. 



This trip found the Channel warming up, and almost arriving at the same degree 

 as the deep isolated lochs which were still passing down the heat of 1886. The open 

 basins, which had cooled more rapidly, had reached their minimum, and so, having just 

 begun to heat up again, were colder than either the free or the nearly completely inclosed 

 areas. 



Loch Lomond and Loch Katrine, fresh water lakes, which were visited just before 

 the Clyde trip, had the temperatures of 41 o, and 40° "2 respectively throughout their 

 whole depth in the deepest parts. 



Trip IX., May 1887. — The observations were made forty-one days after Trip VIII. , 

 and occupied from May 6th to 11th, no work, however, being done on the 8th. In 

 April the air-temperature had been considerably below the average for the season, and 

 snow had often fallen ; but May was, so far as regards warmth, a normal month. From 

 May 1st to 8th the weather was calm, with light and irregular wind. On the 9th it 

 was blowing half a gale from the west, and temperature observations were made in the 

 West and Central Arran Basin, but the rough sea put a stop to the work. On the 10th 

 Loch Fyne was visited with a fresh westerly breeze, blowing, on the whole, up the loch. 

 On the 11th a light down-loch wind was found in Loch Strivan. 



The surface temperature was highest in Loch Fyne and Loch Goi], both of which 

 had cooled down in the lower layers until they were practically of the same temperature, 

 as the slightly warmed mass of the open basins outside, which below 15 fathoms of 

 depth had a temperature of from 45°"0 to 44°*3, the West Arran Basin being somewhat 

 warmer, probably on account of its freer communication with the open sea. In the 

 Channel the temperature of the whole mass of water was 46°. Inside, the surface was 

 everywhere warmer, and the water below 10 fathoms everywhere colder than this figure. 

 As in other cases when a homothermic condition was beginning to be disturbed by 

 surface-heating, there were several instances of intermediate maxima or minima. In 

 Loch Fyne a very feeble indication of the kind of distribution which characterised June 

 and August 1886 was detected, and similar anomalies were noticed on the Great Plateau, 

 in the Arran Basin, and near the head of the Dunoon Basin. Evidently when there is no 

 marked stratification of water due to a heterothermic condition, the disturbing effects 

 of change of salinity would have freer play than at other seasons in determining vertical 

 movements. 



Just before this trip Dr Murray had made an extensive series of observations on 

 the northern lochs of the West Coast and the fresh water lakes of the Great Glen. In 

 a depression of 137 fathoms off Scarba, in the Atlantic, the temperature from surface to 



