(378 DR HUGH ROBERT MILL ON THE 



rainfall had been under the average, and the first three months of 1886 were also much 

 drier than usual for the season, and the prevailing winds had been northerly and north- 

 easterly, conditions which would tend to increase the salinity of the area. Jn March a 

 t'tw rainfall-stations had shown slightly more than the average rainfall, and in April, 

 while the amount of rain falling on the area as a whole was beneath the average, it ex- 

 ceeded the normal amount in a belt, stretching from Greenock and the Ayrshire coast to 

 Lochgilphead. During the cruise the Clyde Sea Area lay under an anti-cyclone, the centre 

 of which lay to the north. The first half of the cruise was almost dead calm, in the latter 

 half north-easterly winds, varying from a light breeze to a gale, were experienced. No 

 rain fell. The Gareloch and the Dunoon Basin were examined on the 13th and 14th, and 

 again on the 21st, and the lapse of a week was found to have produced a remarkable 

 effect on the salinity. In the Gareloch there was practically no change except a slight 

 freshening on the surface at the head of the loch, but in the Dunoon Basin, at Gantock 

 Beacon, the surface density had risen to 1*02420 from 1*01905 in the previous week; 

 part of this increase might be due to the state of the tide, which was near low water on 

 the first and near high water on the second occasion ; but the second salinity was greater 

 than any found nearer than the south of Arran a few days previously. Moreover, off 

 Brodick the surface density was 1*02268 en the 15th and 1*02325 on the 17th, when the 

 tidal phase was nearly the same. Everywhere, except in the Gareloch, there was a rapid 

 increase of salinity in progress, partly, no doubt, by evaporation, partly by the north- 

 easterly wind driving the surface water seaward. Loch Fyne showed the remarkable 

 relation of a steady increase of salinity on the surface from the mouth to the head, where 

 the highest density ever observed, 1*02420, was noted; at the bottom the density 

 gradient was as usual in the opposite direction. Exactly the same state of matters was 

 observed in Loch Strivan, and in both these lochs the wind had been blowing straight 

 down from the head for several days previously. The fresh water had thus evidently been 

 driven out, and the Salter deep layers, raised by reaction, delivered salt water on the 

 surface at the head of these lochs. In Loch Goil and Loch Long, which were visited in a 

 dead calm, the surface water was freshest at the head of the lochs ; and in the latter, at 

 Arrochar, the density was the lowest ever observed, 1*01302, although the previous day it 

 was 1*01813. The difference between bottom and surface salinity was greatest in these 

 lochs, least in the Channel, where the water seemed thoroughly mixed throughout its whole 

 depth. In the Gareloch, also, the difference between bottom and surface density was slight. 

 The seaward portion of the area had a lower salinity than was ever met with again. 



Salinity Trip of June 1886. — This trip took place almost exactly two months after 

 the former, the interval between the central day of each being sixty-one days. Throughout 

 May the rainfall had been greatly above the average in all parts of the Clyde-drainage 

 area, except at Inveraray and Arrochar, but in June not half the average rainfall was 

 experienced. The winds throughout this period were northerly, and from the 16th to 

 the 22nd, while the trip lasted, the northerly winds continued, changing ultimately to 

 north-west and west, blowing strongly, and accompanied by bright sunshine with no 



