CLYDE SEA AREA. 91 



isotherm of 44° is represented as touching the Minard barrier, although there was no 

 observation to fix it, and it may not have come so far down-loch. The line of 44° 

 ran up the section to C.uill at about 12 or 15 fathoms. The temperature at all stations 

 fell steadily to about 20 fathoms where the minimum occurred (at Strachur 42° - 3), thence 

 the temperature rose much more slowly to the lower isotherm of 44°, which ran obliquely 

 from near the lip of Minard Basin until it reached a depth of 50 fathoms at Inveraray. 

 Beneath this was a gradual rise of temperature to 44°*1 or 44°"2. The upper layers were 

 crowded with close parallel isotherms, showing surface heating. The lines of 44°, 43°, 

 and 42° "5 formed a series of closed lenticular curves, near each other above and widely 

 separated below, indicating a mass of isolated cool water entirely surrounded by warmer 

 layers, and separated by the warmer Gortans Basin from water slightly below 44° at the 

 same position (though without the intermediate minimum) in the Arran Basin. 



Were it not for Section I. we would naturally assume that the isolated cold mass 

 represented the winter minimum slowly working its way down through the remnants of 

 the undisturbed warmth of the previous summer, and pursued above by the rapidly 

 increasing warmth of the next summer. But Section I. shows that the whole mass 

 had started at about 41°"8, and that considerable heating had taken place throughout. 

 Hence the problem is to account for the water below 20 fathoms heating up more 

 rapidly than that between 15 fathoms and 10 fathoms. 



Many hypotheses were tested. The wind causing a rotary circulation either 

 transversely or longitudinally might account for it, but there was no record of a pro- 

 longed steady wind likely to produce such a result, and when wind of the kind demanded 

 by this hypothesis occurred, it was not accompanied by similar conditions in the water. 

 No satisfactory conclusion as to the origin of the distribution of temperature has been 

 arrived at. 



The whole mass of water might be supposed to heat up gradually, most rapidly on 

 the surface, until the mass from, say 15 fathoms downward, came to a temperature 

 about 42° *5. Then tidal or wind action might be supposed to fill the Minard Basin with 

 warm dense water at a temperature over 44°, and this crossing the Minard bar with the 

 tide would, in consequence of its density, pour down the slope, warming the lower layers 

 while the fresher upper stratum would be heated sufficiently to maintain it at a less 

 density than the central cold area. This condition once established, would tend to persist. 

 The density observations may be summarised as follows, the densities being given at 

 the temperature of the water in situ. 



[Table. 



