92 



DR HUGH ROBERT MILL ON THE 



Table XXXIII. — Density of Water in situ in Loch Fyne. 



1 Cuill. 



Dunderawe. 



Inveraray. 



Strachur. 



Furnace. 



Otter I. 



April 1886 ■ 



Surface . . 

 Bottom . . 



1-02600 



1-02608 

 626 



1-02576 



1-02605 

 628 



1-02585 

 652 



1-02574 

 669 





r 



Surface . . 



478 



560 



562 



559 



580 



627 





5 Fathoms . 



564 





600 



579 



... 



643 



June 1886 ^ 



10 Fathoms . 

 20 Fathoms . 

 25 Fathoms . 



594 



618 



636 











Bottom 



623 



618 



638 



636 



649 



665 



The density of the water in Loch Fyne attained the actual maximum in June 1886, there 

 being 2 per cent, more pure sea- water present than the average. However, April 1886 

 was also a month of exceptional salinity, the amount of sea-water present in Loch Fyne 

 then being 1'3 per cent, above the average. In April the difference between the density 

 in situ of surface and bottom water, expressed in units of the fifth decimal place, 

 was 18 at Dunderawe, 23 at Strachur, 66 at Furnace, and 95 at Otter. These 

 differences corresponded to an increasing difference in salinity between surface and 

 bottom water as the Arran Basin was approached, due to the greater salinity of the 

 bottom water seaward, the surface salinity on this occasion being nearly the same along 

 the whole length of the loch. It is difficult to understand in the light of Table XXXIII. 

 how density would account for the continuance of the cold layer of intermediate water, 

 because at Inveraray the salinity [i.e., density at 60° F.) of the water at 25 fathoms 

 was r02465, and at the bottom 1*02486, a difference of 21, while the actual density 

 in situ at 25 fathoms was in consequence of its low temperature, 1*02636, whilst 

 that at the bottom was only 1*02638, and at the bottom at Strachur 1*02636, leading 

 one to expect the formation of convection currents, or at any rate the rapid suppression 

 of the intermediate minimum. The fact that a similar arrangement of temperature never 

 occurred again, except to a very slight extent, which could be readily explained by local 

 heating, points to some special circumstance in the Spring of 1886 as the cause. The 

 surface salinity of the Loch Fyne stations was higher in June 1886 than on any 

 subsequent occasion, and the same was true of Loch Strivanhead, while the Arran Basin 

 was scarcely above its average, thus indicating the possibility of mixture with lower- 

 layers, and hinting at vertical circulation through wind action. But any argument drawn 

 from this difference is weakened by the fact that in April 1886 the contrast in salinity 

 between Loch Fyne and the Arran Basin was much greater, the surface water of the 

 Basin being then actually fresher than that of the loch. 



