CLYDE SEA AREA. 97 



to 45 0, 3. The centre of this layer of maximum temperature being nearer the surface than 

 that of Section XVI. , shows that it is not a result of continuously progressive cooling, but 

 rather due to some more abrupt changes. The marked cooling down to the bottom indi- 

 cates a once continuous cooling from the surface ; the intermediate thin zone of warmer 

 water possibly is all that remains of a surface heating due to warm weather, which, with 

 the recurrence of cold, was capped by a chilled layer. The range of temperature in 

 Gortans Basin and seaward is too slight to be discussed. 



Section XVIII., 22nd-2Srd March 1888. — A return to the nearly uniform conditions 

 of the minimum is shown here. The temperature varies from something under 43° on the 

 surface to something over 44° on the bottom. There are traces of a slight intermediate 

 minimum in Gortans Basin, and the accumulation of warmer water on the bottom of the 

 Arran Basin between Otter and Kilfinan is marked, as on several occasions of the approach 

 to minimal conditions. 



Section XIX., 2nd-Ath June 1888. — Cooling has continued at the bottom, where the 

 temperature in the Upper Basin is now 43° "3, but rapid heating has gone on from above 

 downward without the formation of any trace of an intermediate minimum. The section 

 is largely hypothetical, as no observations were made at Furnace, Minard, or Otter. 



Sections XX. and XXI. (Partial Sections), 2ith-25th August 1888 ; XXII, 

 27th August 1888. — On the 24th there was a rapid fall from 60° on surface to 54° at 1\ 

 fathom, a gentle fall (50° at 15 fathoms) to 48° at 22 fathoms, rapid fall to 46° at 23|- 

 fathoms, and finally a gentle fall to 44° at 35 fathoms. 



On the 25th the surface temperature was somewhat higher, and the fall of temperature 

 at the greater depths much more uniform, the crowded isotherms 48°-46° being in par- 

 ticular well spread out. The range of temperature was remarkable. 



On the 27th the downward propagation of warmth was very clearly marked ; and the 

 surface layers having cooled somewhat, an intermediate maximum was formed at about 3 

 fathoms at the head of the loch. 



Section XXIII, 16th, 17th, 18th, and 19th October 1888.— This section was compiled 

 from observations scattered over too long a time to be of much value. It appears to show 

 the characteristic signs of a flow of warm water from the Gortans Basin over Furnace 

 brow into the Upper Basin. The upper strata of water are assuming the homothermic 

 form common in autumnal coolino-. 



The difference between the thermal changes in the Arran Basin and Loch Fyne is 

 mainly due to the restricted entrance and the much steeper slope within the sill preventing 

 the free mixture of the water from outside, and also to the low salinity of the surface 

 water in the upper reaches. The resemblance of the Channel and Plateau to the 

 Gortans Basin is very strong. The up welling at Otter keeps the Gortans Basin supplied 

 with nearly homothermic water of much greater salinity than that found at the same 

 depth in the Upper Basin, but on account of the steep slope beyond Furnace this water 

 appears to spread over the cold layers of Loch Fyne, instead of following the ground and 



VOL. XXXVIII. PART I. (NO. 1.) N 



