'04 



DR HUGH ROBERT MILL ON THE 



vertical section at each station along the axis of the loch and neighbouring parts of the 

 Arran Basin, are shown in the form of curves in Plate XII. 



The figures of Table XXXII. may be put in the form of percentages of normal sea 

 water present, and this is done in Table XXXIII. 



Table XXXIII. — Percentage of Normal Sea Water (Density T0260) in Loch Fyne 



at Various Dates. 



Date. 



Cuill. 



Dunderawe. 



Inveraray. 



Strachur. 



Furnace. 



Gortans. 



Otter. 



Kilfinan. 



Skate Isld. 



April 1886, 



93-5 



94-0 



93-8 



939 



94-8 



95-0 



95-1 



95-1 



95-2 



June „ 



94-2 



943 



95-0 



95-0 



95-1 



95-5 



96-0 



96-2 



96-2 



August „ 



900 



9T2 



92-1 



94-0 



94-7 



95-5 



95-8 



96-3 



96-7 



November „ 



82-7 



85-4 



911 



90-8 



92-7 



93-5 



94-2 



94-7 



94-9 



December „ 



88-5 



90-0 



92-2 



93-4 



93-2 



93-8 



94-9 



95-5 



95-8 



February 1887, 



80-4 



87-7 



90-8 



92-0 



92-0 



92-0 



94-2 



942 



94-2 



Marcb „ 



80-7 



89-0 



91-8 



91-9 



91-6 



93-0 



93-4 



94-8 



95-1 



May 



88-8 



92-4 



92-7 



93-0 



937 



94-7 



95-0 



952 



955 



June, „ 



88-0 



91-6 



92-0 



94-5 



94-5 



95-0 



95-8 



96-2 



96-7 



July 



927 



93-8 



93-6 



94-9 



94-7 



95-0 



95-7 



96-0 



96-9 



September „ 

 Mean, . 



92-0 



92-7 



934 



93-8 



94-2 



95-2 



95-6 



96-7 



95-8 



88-3 



91-0 



92-6 



93-4 



937 



94-4 



951 



95-5 



957 



Calculating from these results, itis easy to find the approximate percentage of normal 

 sea water and of fresh water in the loch at any given time. Since the volume of the 

 loch from Cuill to Otter is known to be almost exactly half a cubic sea mile, and the total 

 drainage area of its basin, including the water surface, to be 167*64 square sea miles, the 

 percentages can be reduced to actual volumes, and the volume of the inflowing fresh 

 water between any two periods of observation expressed in inches of rain over the area. 

 In Table XXXIV., which gives the results of the calculation, evaporation is expressed as 

 negative rainfall. 



The last column in the table gives the average of the rainfall at Inveraray, Arrochar, 

 Ardrishaig, and Kilmory, as nearly as can be calculated for the intervals between the 

 successive trips. In looking at Loch Fyne with reference to the interchange and 

 mixture of sea and fresh water, it is necessary to observe, that evaporation may be viewed 

 as negative rainfall, or as a rainfall of sea water, since we assume in this discussion that 

 the level of Loch Fyne remains in equilibrium with the Arran Basin. But in addition to 

 the increase of the proportion of normal sea water by evaporation, there is an increase due 

 to actual inflow during flood-tide of Salter water from the Arran Basin, in which the 

 fluctuations of salinity are much less. This inflow brings, on the average, about 9 5 '5 per 

 cent, of its volume of sea- water and 4 '5 per cent, of its volume of fresh water. Thus, if 

 by an exceptionally dry season prevailing over the Loch Fyne drainage area, the water 

 in Loch Fyne had become concentrated to a higher degree than 9 5 "5 per cent, the inflow 

 from the Arran Basin would count as a contribution of fresh water and not of sea water. 



