46 



DR HUGH ROBERT MILL ON THE 

 Table X. — Temperature Observations off Carradale. 



No. . . 



1 



2 



3 



4 



5 



6 



7 



8 



9 



10 



lit 



12 



Date . . 



20.9.78 



25.8.85 



19.6.86 



13.8.86 



26.9.86 



18.11.86 



24.12.86 



11.2.87 



30.3.87 



9.5.87 



12.5.87 



18.6.87 



No. of Pts. 



13 



7 



9 



13 



10 



12 



9 



6 



9 



6 



10 



15 



Temp. . . 



52-9 



50-8 



45-1 



48-5 



50-9 



51-0 



47-5 



43-6 



43-8 



44-9 



45-2 



47-8 



Slope . . 



+ 4-1 



+ 5-8 



+ 5-0 



+ 6-2 



+ 4-4 



-2-0 



-1-0 



-0-9 



o-o 



+ 2-5 



+ 1-6 



+ 6-9 



H.D. . . 







30 



40 



20 



30 



25 



50 



60 



75 



45 





25 



Ji.t. . . . 





49-3 



44-0 



47-0 



49-2 



51-5 



47-7 



43-7 



43-8 



44-2 





46-2 



No. . . 



13 



14 



15 



16 f 



17 



18 



19 



20 



21 



22 



23 





Date . . 



7.7.87 



17.8.87 



22.9.87 



3.11.87 



5.12.87 



9.12.87 



23.12.87 



28.12.87 



30.1.88 



15.2.88 



22.3.88 





No. of Pts. 



12 



12 



9 



13 



16 



15 



9 



15 



9 



12 



12 





Temp. . 



48-7 



51-0 



52-7 



51-2 



48-8 



47-9 



46-0 



45-9 



44-8 



44-4 



42-5 





Slope . . 



+ 8-1 



+ 8-4 



+ 3-8 



-2-1 



-0-2 



-0-3 



-1-3 



-1-8 



-0-2 



-0-8 



-1-0 





H.D. . . 



40 



40 



30 



30 



80 



80 





60 



80 



40* 



35 





h.t. . . . 



47-1 



48-9 



51-6 



52-1 



48-8 



47-9 





46-1 



44-8 



44-2 



42-8 





Assume 80 fathoms as depth. 

 * Here the homo-thermic 40 fathoms were the upper half, f Observations made by F.C. " Vigilant.'' 



In Table X. two data are tabulated which acquire much importance in the Arran 

 Basin. These are the homothermic depth (H.D.), i.e. the depth of the mass of water in 

 which the whole range of temperature is less than 0°*5. This is almost always the lower 

 part of the water, and in order to arrive at comparable results the depth is assumed as 

 80 fathoms in all cases (although occasionally the sounding may have been in slightly 

 shallower, and sometimes in slightly deeper, water), and the homothermic depth is arrived 

 at by subtracting from 80 the depth in fathoms at which the homothermic part begins. 

 The second datum, h.t., is the mean temperature of the homothermic layer. Incidentally, 

 this is, of course, the mean temperature of the lowest five fathoms, so that by adding 

 (algebraically) the slope, the mean temperature of the upper five fathoms is at once 

 obtained. 



Observations 1 and 2 of Table X. were made by Mr J. Y. Buchanan, F.R.S., in 1878 

 and 1885 respectively; Nos. 11 and 16 were done on the Fishery cruiser "Vigilant" 

 in 1887 ; the remainder were all done on the "Medusa." 



The curves were practically homothermic in the cold months, December to March. 

 During the period of heating, May to August, the positive slope of the curves greatly 

 increased, the homothermic layer shrunk until it occupied the lower third only, and the 

 form of the curve was practically a paraboloid, although occasionally very irregular in 

 outline. The upper part of the curve then assumed a negative slope, and the water 

 rapidly became homothermic as the minimum approached. 



