24 DR HUGH ROBERT MILL ON THE 



in the form of a layer extending from 25 fathoms to the bottom at Kilfinan, but thinning 

 away until at Inchmarnoch it was only 10 fathoms thick, and surrounded above and 

 below by warmer water, evidently influenced by the ocean. A like remnant of colder 

 water was found in a similar position at the head of the Dunoon Basin. The deep 

 lochs were comparatively little affected by the rapid rise of air temperature. In Loch 

 Fyne the minimum, not quite at the bottom, was 45°, and in Loch Goil the minimum 

 at the bottom was 44°"9. The Gareloch was, as a whole, the warmest division of the 

 Area, but high surface temperatures were found in all the sea-lochs, the absolute maximum 

 being 60° in Loch Long. The influence of a long spell of hot dry weather on narrow 

 waters is obviously not confined to the incidence of solar radiation on the surface. The 

 water flowing in from the land is heated up by trickling in shallow streams across the 

 hot rock or sand, and this influence is evidently cumulative. The longer the hot dry 

 weather continues, the more potent is it to raise the surface temperature of the water, 

 the diminished influx of fresh water being more than made up for by the enhanced 

 temperature of the affluents. 



Trip XI., July 1887. — This was a short trip, confined to the West and Central Arran 

 Basins and Loch Fyne. It only occupied three days, July 6th to 8th, and was twenty- 

 two days later than the June trip. The weather of July, as a whole, was almost as much 

 above the average with regard to air-temperature as that of June had been. On the 

 cruise, each day was calm; or with very light breezes ; the 6th was dull and showery, 

 the other days bright and warm. On this occasion, in the Central Arran Basin, an effect 

 common on all calm summer-days was exceptionally well developed. The air blowing 

 as a gentle breeze off the land, swept across the water in hot puffs, laden with the scent 

 of heather, which could not be perceived at all in the perfectly calm intervals between 

 the breezes. The surface temperature of the water averaged about 56°, in Loch Fyne 

 exceeding 60°. The water coming in from the Channel had the temperature of 56° on the 

 surface and 50° at the bottom on the outer edsje of the Great Plateau in 30 fathoms. In 

 the West Arran Basin it was evident that this warm water was doing more than surface- 

 heating to warm up the lower layers. The deeper layers of Loch Fyne were, as usual, 

 the coldest, but were heating uniformly, showing none of the eccentricities of the 

 previous summer. 



In the course of this trip a number of experiments were made on the rate of descent 

 of the brass messengers used to reverse thermometers, and on the correction to be applied 

 to thermometers read at higher temperatures than those at which they were reversed. 

 These results are treated of at pp. 7-8. 



From July 12th until August 12th I was engaged in a special research for the Fishery 

 Board for Scotland into the physical condition of the fishing-grounds on the north-west 

 coasts of Scotland. I made observations on July 13th on Loch Torridon from H.M.S. 

 "Jackal," and found the water in the lower loch to vary from 56° on the surface to 49° 

 at 65 fathoms. In the more isolated upper loch, the surface temperature was 61°, and 

 that at 45 fathoms 51°. On the following day, observations made in the Minch 



