CLYDE SEA AREA. 95 



fathoms, and warms to 44° 7 at the bottom, but this intermediate minimum is much less 

 marked than in the previous year. 



Section X., 15th~16th June 1887. — Continued heating has taken place, and in all parts 

 of the section the water now falls gradually in temperature from surface to bottom, all 

 trace of an intermediate minimum having vanished from the Upper Basin, the bottom 

 water in which is, however, a little colder than in the Arran Basin. In the Upper Basin 

 and in the Arran Basin the isotherms on the whole dip seaward, but in the Gortans Basin 

 they dip landward. From Kilfinan to Gortans the disturbance due to the narrow Otter 

 bar is apparent, strong upwelling taking place, while curiously enough there is no dis- 

 turbance of the isotherms at the Minard passage. Indeed, here Furnace seems the true 

 boundary of the Upper Basin, as the isotherm of 46° reaches the bottom there, and the 

 water down to the bottom remains much over 46° all the way to Otter, beyond which it 

 again sinks. Here at depths below 25 fathoms the Gortans Basin, extended to Furnace, 

 separates two masses of water below 46° by a slice, the temperature of which is from 47° 

 to 46°*8, and the line of 48° sinks deeper in this basin than anywhere else in the section, 

 although the surface temperature above it is only 51° as compared with 57° and 58° 

 beyond Strachur. This is unmistakably a result of the mixed water pouring in past 

 Otter. 



Section XL, 7th-SthJuly 1887. — Here the conditions of Section X. are accentuated, 

 except the upwelling at Otter, which is scarcely marked. 



The surface water at many points is over 60°, forming a very thin hot skin covering 

 the characteristic distribution. In the Upper Basin the isotherm of 50° lies at the depth 

 of about 5 fathoms, scarcely 1 fathom deeper than in June. The isotherm of 46° is only 

 a fathom or two deeper than in June at Strachur and Inveraray, while at Furnace, 

 Dunderawe, and Cuill its position is unchanged, but temperature exceeds 45° down to 

 the bottom, thus showing a slight warming. The very slight effect of the high surface 

 temperature is remarkable. Still more striking is the crowding downward of the 

 isotherms at Furnace, and to a less extent at Otter, leaving the Gortans Basin filled with 

 a huge wedge of water from 1° to 2° warmer than that at like depths outside and inside. 

 The approach to horizontality of the Upper Basin isotherms below the level of the 

 Furnace brow, and the rapid seaward dip of those above it, suggest the advance of a body 

 of warm water and its mixing by lateral translation. As no observations were taken 

 between Furnace and Minard the precise landfall of the isotherms is not known, and the 

 character of X. and XL may be of much more common occurrence than appears in 

 the earlier sections. 



Section XII., 15th-16th August 1887. — The surface has cooled down a few degrees, but 

 the mass of the water has warmed notably. The isotherm of 50° has sunk to the bottom 

 in the Gortans Basin and to 30 fathoms in the Arran Basin, while from Furnace it curves 

 up toward Cuill. The upwelling at Otter is very slight. The isotherms are closely 

 clustered in the surface zone of 7 fathoms (55° to 52°), then spread more uniformly, 

 clustered again about 25 fathoms (50° to 47°), forming a Sprungschicht at Furnace and 



