12 



DR HUGH ROBERT MILL ON THE 



positive or negative S-shaped curve, and the positive or negative sickle-shaped curve. 

 The contorted curve, as the extreme case of heterothermicity representing superimposed 

 layers of water at different temperatures, may also be mentioned. Examples of these are 

 given in fig. 3 (Plate XXII.). 



Air Temperature. — For the distribution of air- temperature I depend on the data 

 supplied by Dr Buchan, which are published in Part I. The air-temperature observa- 

 tions, made by a sling thermometer at the time of each temperature-sounding, are of 

 course affected by the diurnal range to an enormously greater degree than is the 

 water-temperature. It is therefore impossible to apply them in any general way. 

 Table III. gives an approximation to the mean air-temperature of the Clyde Sea Area 

 for the three years under observation, by combining observations from selected stations ; 

 and the results are shown graphically compared with the long period mean (1866-1885), 

 by the curve, fig. 2, Plate XXII. In this and other curves of seasonal variation the 

 mean value for the month is placed on the line indicating the central day of that 

 month. 



Table III. — Mean Temperature of Air over Clyde Sea Area. 



1886. 



Station. 



Jan. 



Feb. 



Mar. 



A.pril. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



Year. 



Glasgow, . 



34-6 



34-8 



38-6 



44-4 



48-8 



54-2 



57-6 



57-0 



52-8 



50-4 



44-4 



34-0 



46-0 



Helensburgh, 



36-8 



36-5 



38-2 



44-0 



48-2 



54-4 



57-8 



56-8 



52-7 



51-1 



45-4 



36-3 



46-5 



Dumbarton, 



35-2 



34-8 



37-6 



44-4 



48-0 



54-3 



57-8 



56-3 



53-2 



50-3 



43-2 



33-8 



45-7 



Greenock, . 



354 



34-8 



37-4 



43-2 



47-2 



53-4 



56-8 



56-7 



53-0 



50-3 



44-2 



35-0 



45-6 



Rothesay, . 



36-0 



36-6 



39-0 



45-0 



47-8 



53-9 



56-6 



56-2 



53-5 



51-1 



45-0 



36-0 



46-4 



Lamlash, . 



39-4 



37-1 



38-0 



44-0 



47-6 



53-2 



56-1 



55-9 



53-8 



51-0 



46-5 



38-6 



46-8 



Pladda, 



Mean, 



37 



38-3 



38-0 



44-1 



47-4 



52-1 



55-7 



55-6 



53-6 



51-7 



46-3 



38-0 



46-5 



36-3 



36-1 



38-1 



44-2 



47-9 



53-6 



56-9 



56-4 



53-2 



50-8 



45-0 



36-0 



46-2 





1887. 



• 







Glasgow, . 



38-9 



4C0 



39-4 



43-5 



51-1 



58-9 



60-1 



57-4 



52-6 



45-1 



40-4 



37-3 



47' 1 



Helensburgh, 



37-5 



39-3 



37-8 



41-7 



48-4 



S 8-o 



6o - o 



57"° 



52-0 



43-6 



39-4 



35-8 



45'9 



Dumbarton, 



38-1 



40-0 



38-8 



43-1 



50-1 



58-4 



60-3 



57-1 



52-2 



45-3 



41-5 



37-0 



46-8 



Greenock, . 



38-8 



40-0 



38-7 



43-0 



49-7 



58-8 



61-0 



57-1 



52-4 



45-5 



40-8 



37-3 



46-9 



Rothesay, . 



39-0 



41-7 



40'o 



43-8 



50-6 



58-4 



59-4 



57-1 



53-2 



46-1 



41-8 



37-6 



47 '4 



Lamlash, . 



40-6 



41-7 



40-1 



42-9 



49-6 



58-7 



58-7 



57-2 



52-4 



46-2 



43-1 



393 



47-5 



Pladda, . 

 Mean, 



40-5 



41-6 



40-7 



43-2 



49-9 



58-8 



58-9 



57-4 



53-1 



46-3 



42-2 



38-8 



47-6 



39-1 



4o - 6 



39'4 



430 



49-9 



5 8-6 



59'8 



S7'2 



52-6 



45-4 



41-3 



37-6 



47 -o 



Note. — Figures in this type — 473 — are approximate only. 



