CLYDE SEA AREA. 



141 



face to 49 0, 8 at the bottom. The state of matters is similar to that common at the same 

 season in the Gareloch, but not shown in the deeper lochs. A light breeze was blowing, 

 varyino- from east to south-east ; but, of course, the section affords no evidence of 

 circulation. 



Taken as a whole these sections show that Loch Strivan is, from its physical and 

 o-eooraphical peculiarities, the most subject of all the Clyde lochs to have its waters 

 mixed and set in motion by the wind. 



Seasonal Variation of Temperature. — Fig. 49, Plate XXXII., shows the seasonal varia- 

 tion of the temperature of the air at Rothesay, and of the water of Loch Strivan, considered 

 for the superficial layer of 5 fathoms, the deepest layer between 30 and 40 fathoms, 

 and the mass of the water taken as a whole, the temperatures being calculated from the 

 sections. 



The relations between these curves differ entirely from those of Loch Goil or Loch 

 Fyne, showing a resemblance rather to the curves of the more open Basins. The retarda- 

 tion of the date of maximum temperature, after that of the air, was for the superficial 5 

 fathoms 45 days, and for the bottom 10 fathoms 105 days, in 1886 ; the corresponding 

 figures for 1887 were 39 and 119 ; an average for the two years of 42 days for the 

 surface, and 112 days for the bottom layer. The average retardation of the maximum 

 was 165 days in Loch Goil, and 123 days in Loch Fyne, at the depth of 30 to 40 fathoms, 

 indicating the more rapid circulation of Loch Strivan. 



The periods of heating and cooling of the mass of water in Loch Strivan — calculated 

 from the curve — may be compared with those of the other divisions given in Table XLV. 

 The time is in days ; the rate, degrees per day. 



Table LV. — Period of Heating and Cooling, and Daily Bate of Change of 

 Temperature, in Loch Strivan. 



Heating, 

 1886. 



Rate 

 per 

 day. 



Cooling, 



1886-87. 



Rate 

 per 

 day. 



Heating, 



1887. 



Rate 

 per 

 day. 



Cooling, 

 1887-88. 



Rate 

 per 

 day. 



Heating, 



1888. 



Rate 

 per 

 day. 



180 



0-060 



155 



0-059 



202 



0-049 



198 



0-052 



186 



0-050 



The minimum and maximum temperatures of the mass of water, so far as they can 

 be deduced from the curves, are :— 41°"8, April 15th, 1886; 52°'4, September 26th, 

 1886; 43°-3, March 1st, 1887; 53°% September 18th, 1887; 42° -9, April 4th, 1888; 

 and 52 0, 2, September 27th, 1888. In duration and rate these figures correspond best 

 with those of the Arran Basin. Considering the two periods which can be compared in 

 all the divisions, we find the average number of days of heating and cooling respectively 

 to be — 191 and 177, or in the ratio of 100 to 93. In this respect — the greater duration 

 of heating than cooling — the affinity is with Loch Fyne, where the ratio was 100 : 91, 

 rather than with the Arran Basin, where it was 100 : 100. 



