90 DR HUGH ROBERT MILL ON THE 



Strachur, and below that they are widely spaced. The bottom water of the Arran Basin 

 is now 2° warmer than that in the Upper Basin of Loch Fyne. The drawing of the 

 section between Minard and Furnace is conjectural, and probably incorrect. 



Section XIII., 23rd September 1887.— Surface temperature has changed but slightly 

 since August, while all the lower isotherms have sunk in fair proportion, indicating a 

 general warming of the lower layers. 50° has reached 60 fathoms at Skate Island and 

 30 fathoms in the Upper Basin, while the whole Minard Basin is over 52°. The gathering 

 in of isotherms at the bottom at Furnace is more marked than ever, the change from 51° 

 to 48° being compressed into 2| fathoms compared with 15 fathoms at Inveraray and 

 30 fathoms at Kilfinan. 



Here the pouring in of warm water of uniform temperature seems to take place 

 directly over the cold uniformly-temperatured layer sheltered from mixture by the 

 Furnace brow. 



Section XIV., 5th November 1887. — This is a partial section from Strachur to the 

 head of the loch. Below 25 fathoms the water has warmed steadily since Section XIII. 

 Above 25 fathoms it has cooled most rapidly on the surface, which is at 46°. The 

 temperature rises rapidly to 50° at about 6 fathoms, then slowly for a fraction of a 

 degree, cools down again to 50° at 23 fathoms, and 49° at 40 fathoms. An excellent 

 example of winter cooling in calm weather, leading to the inclusion of an intermediate 

 maximum. 



Section XV., 7th November 1887. — In the interval from XIV. a strong gale from 

 north-east (down-loch) prevailed, and the contrast of conditions is singularly instructive. 

 The isotherm of 49° still runs straight across at 40 fathoms, and below it the condition 

 as regards temperature is absolutely unchanged. But above 40 fathoms every trace of 

 thermal stratification has vanished. The temperature rises uniformly to 49° "8 at the 

 surface. Thorough mixture has taken place down to, but not below, the level of the 

 brow at Furnace. This indicates that below 40 fathoms the Upper Basin is extremely 

 isolated, and that complicated circulation and complete mixture may occur in the upper 

 layers without disturbing the depths. 



Section XVI, 10>th-l7th December 1887. — The bottom water has warmed up to a 

 little over 46°; the surface water has greatly cooled down, especially toward the head of 

 the loch, and there is a rise of temperature from the surface to 48° about 17 fathoms. 

 Nearly constant temperature (a little higher) prevails to 44 fathoms, where it sinks to 48' 

 again, and then falls uniformly to the bottom. Seaward of Furnace the surface tem- 

 perature ranges from 46° to 47°, but up the loch it falls steadily to 38°*2 at Cuill. The 

 isotherms of 48° in the Upper Basin show a tendency to define a lenticular mass of 

 warmer water, conceivably the remains of the great mixing of November 7th. 



Section XVII, 14th February 1888. — Great changes have occurred since Section XVI. 

 The surface of the Upper Basin has cooled down to 42° or less, rising rapidly to 46° at 5 

 fathoms, reaching a slightly higher maximum about 10 fathoms, falling to 46° again at 

 18 fathoms, and from that position to the bottom remaining nearly constant, falling only 



