CLYDE SEA AREA. 19 



influence is greater than that of solar radiation is perfectly shown by the very much 

 slower rate of warming in the masses of water cut off from free communication with the 

 ocean, but more exposed in every way to solar power from the much greater influence 

 on their waters of the heated land and warm surface drainage. 



The process of heating-up from a practically uniform coldness in all parts of the Area 

 has so far brought out month by month with increasing distinctness the enormous power 

 of physical configuration in dominating thermal changes, — none the less because the 

 process of heating-up was probably retarded on account of the abnormal coldness of the 

 whole spring and summer. The average temperature of each vertical sounding, the 

 surface temperature, and the temperature at 30 fathoms are given on map 2, Plate XXL, 

 as a typical example of the distribution of warmth at the autumn maximum. 



Trip V., November 1886. — This trip, fifty-two days later than that of September, 

 occupied the time from November 11th to 18th, excluding the 14th. It commenced to 

 take account of the cooling-down consequent on the excess of radiation from the surface 

 after sunset over the radiation to the surface during day-light. The typical character of 

 the observations was rather spoiled by the exceptional warmth of the air in October and 

 November, the mean of each month being about three degrees above the average. This 

 was particularly the case in the landward portion. The rainfall of October was much 

 below the average. Easterly winds were common, with frequent storms, and the weather, 

 although unusually bright, was disturbed. From November 1st to 4th there were strong- 

 south-westerly and westerly winds. The early part of the cruise was favoured with fine 

 weather, calm and showery, with snow on the hills. The landward portion, Loch Fyne 

 excepted, was examined in these conditions. On the 14th, when no work .was done, 

 there was a south-westerly gale; on the 15th the Kyles of Bute and East Arran 

 Basin were worked in a stiff south-westerly breeze. The 16th and 17th were squally, 

 and on these days the West Arran Basin and Loch Fyne were visited. The 18 th being 

 calm, though hazy, was devoted to the Great Plateau, and on the 19th work was stopped 

 by a gale from the south-west. 



Surface-cooling was in progress everywhere. The whole mass of water beyond the 

 Plateau had cooled down to about 50° "5, but was still warm enough to exercise a 

 distinctly warming action on the deep water of the southern end of the Arran Basin, 

 although the surface of that basin had cooled to a lower temperature. Excluding the 

 extreme instances of highland isolation, Lochs Goil and Fyne, the average temperature 

 of the Area at the surface was 49° "5, and at the bottom 51° - 5. Thus while the whole of 

 the shallow water and of the Dunoon Basin had cooled down from three to six degrees 

 since September, in the Arran Basin the temperature at 25 fathoms was the same as 

 during Trip IV., and below that depth there had been a marked heating. The slope of 

 the curves of vertical temperature had, in fact, been inverted, and assumed the negative 

 or winter form, the maximum temperature being at or near the bottom. 



In Loch Fyne and Loch Goil surface-chilling had set in strongly, but the bottom 

 water remained cold (44°'5 to 45°'5), and the result was a warm intermediate layer, 



