20 DR HUGH ROBERT MILL ON THE 



losing heat upward to meet the coming winter's cold, and passing on heat downward to 

 neutralise the cold of the past winter, which had remained as in an ice-house all summer 

 under the ill-conducting blanket of water cut off from free circulation. 



Trip VI, December 1886. — Forty-one days separated the middle of Trip V. from that 

 which lasted from the 22nd to the 30th of December. The exceptional warmth of 

 November had given place to an exceptionally cold December, the mean temperature of 

 the air over the Area being 3° below the average. The latter part of November had been 

 wet and stormy, and December also had the usual character of a West Coast winter month, 

 with strong variable winds and much rain. During the trip every kind of weather was 

 experienced. Loch Long, Loch Goil, and the upper part of the Dunoon Basin were 

 studied on the 22nd, with a fresh northerly breeze and heavy rain ; the rest of the Dunoon 

 Basin and Loch Strivan on the 23rd, with light varying airs. On the 24th in West Arran 

 Basin a stiff breeze blew from the N.W., and on the 25th on the Great Plateau and Channel 

 a gale sprang up from the S.W. On the 26th and 27th the Arran Basin was worked 

 through in calm haze with snow-showers, on the 28th a westerly gale with heavy squalls 

 drove the " Medusa " into the Gareloch, and the 29th and 30th allowed Loch Fyne to be 

 examined in bright, calm weather, the hills snow-clad, and the surface of the loch in some 

 places coated with ice. The distribution of the ice and its physical conditions have been 

 already described (see Part II. p. 681). Under the ice, at the depth of 2 inches, the 

 temperature was 35°"9, and at 6 inches 41°, showing the extreme thinness of the cold upper 

 layer. 



During this trip the temperature of the air was much lower than that of the water, 

 and a number of curious mirage-effects were observed, the Irish coast appearing elevated 

 above the water, and steamers seeming to be pursuing their course underneath the land. 

 The w r ell-known appearance of Ailsa Craig as a mushroom was also clearly seen. Cooling 

 had gone on steadily from the surface throughout, but, except near the heads of lochs 

 and in shallow water, the surface warmth ranged between 45° and 47°, the lower layer 

 being everywhere warmer, and in the open basins the maximum occurred at the bottom. 

 In Loch Fyne the bottom cold layer was thinned down, but had not disappeared, and 

 Loch Goil showed the same effect in a less prominent way. In the North Channel the 

 water was warmer than anywhere else, 48°*5 from surface to bottom, but the effect of 

 surface- cooling made itself felt on the Great Plateau and in the whole of the rest of the 

 Area. It is evident that the influence of the tide is a warming one, even in December, 

 the ebb carrying out the cold surface water, and the flood carrying in warmer oceanic 

 water. 



Trip VII , February 1887. — Observations were made between the 3rd and 12th, 

 excluding the 6th, and the trip was forty-three days after that of December. Air- 

 temperature during January had been close to the average for that month, and in 

 February it was decidedly higher, although in the latter month there was a good deal of 

 snow on the surrounding land. The weather in the earlier part of the cruise was under 

 the influence of a cyclone producing strong winds from the west on the 1st, south on the 



