714 DR HUGH ROBERT MILL ON THE CLYDE SEA AREA. 



tion of sulphates as the average rivers of other regions of crystalline rocks do, it would 

 necessarily happen that if the tidal or wind circulation was insufficient to produce a 

 .somewhat rapid change of water, the proportion of sulphates would be increased by 

 evaporation, and the loch-basins would thus become richer than the open sea in these 

 constituents. The figures before us only serve to suggest, not to solve, these problems ; 

 and the high proportion of sulphates in the Sea Area, compared with the North Sea and 

 the open ocean, becomes very perplexing. 



The average alkalinity of surface water is almost always greater than that of bottom 

 water, and the alkalinity of the Landward portion of the area is distinctly higher than 

 that of the Seaward portion. This is what may be expected from the distribution of 

 salinity, and it shows that the dissolved carbonates of river water produce a marked 

 effect in the composition of the water of the Area. The Gareloch, Loch Goil, and the 

 upper basin of Loch Fyne are characterised by high alkalinity both at surface and 

 bottom. Skate Island has also high surface alkalinity, but at the bottom it is much 

 below the average. The great depth of the water (107 fathoms) may possibly account 

 to some extent for this observation. Carradale in Kilbrennan Sound showed a very 

 high alkalinity at the bottom, which it is difficult to explain. 



Peculiar interest is attached to Mr Dickie's figures for the station at Gantock in the 

 Dunoon Basin. The proportion of sulphates found in the water there was very high, 

 particularly at the bottom, while the alkalinity, especially on the surface, was also the 

 highest observed. It seems to me possible, or even probable, that this is in consequence 

 of the large quantity of alkali waste discharged into the Dunoon Basin. The insoluble 

 calcium sulphide would naturally accumulate as sediment in the deepest part of the 

 basin, where the observations appear to show that it is undergoing gradual oxidation into 

 sulphate. Possibly the high surface alkalinity is due to traces of alkaline carbonates, or 

 perhaps even to soluble sulphides, which were dissolved before the sediment had time to 

 sink. Here, again, the observations only suggest, but do not demonstrate, an explana- 

 tion. 



It is somewhat remarkable that so prolonged, wide-spread, and careful a set of 

 analyses as those of Mr Dickie do not show more direct relations with the remarkably 

 contrasted physical conditions of the regions from which the samples worked upon were 

 taken. I confess to much disappointment with the results ; but, in the hope that others 

 with greater skill or courage in the treatment of statistics than I possess may be induced 

 to look into the matter, I am induced to publish my discussion of the work so far as it 

 lias gone. 



