REPORT ON ATMOSPHERIC CIRCULATION. 



13 



TABLE showing the Diurnal Oscillation of the Barometer in June, in Thousandths 



of an Inch. 



The Heavy Figures show a pressure above, the Italic Figures below, the Means. 



In the British islands, the curve most characteristic of insular climates is that of 

 Valentia, and that most characteristic of continental climates is the curve for Culloden, 

 these two curves being nearly throughout the reverse of each other. The times 

 of occurrence of the morning maximum are respectively 1 p.m. and 7 A.M., or six 

 hours apart. A comparison of the curves for Kew and Culloden, and of these with 

 the curves for Katherinenburg and Fort Eae, in the interior of the continents of Asia 

 and North America respectively, is very interesting. In insular situations, the morning 

 minimum is unusually large, whilst the afternoon minimum becomes, in the more 

 strictly insular situations, so small as almost to disappear ; but, on the other hand, in 

 continental situations, the afternoon minimum is strongly pronounced, whilst the 

 morning minimum tends to vanish, and in many cases disappears altogether, — of which 

 Fort Eae is an example (fig. 15),— thus reducing the phenomena to one daily tide. 



It is to be specially noted that the morning maximum attains the time of greatest 

 retardation in June, when the sun is highest in the heavens, and not in July, when 

 nearly all meteorological conditions show one of their two most prominent annual 

 phases. From this result, the important conclusion follows that the phenomena of the 

 diurnal barometric range are not cumulative, but that in their relation to the sun they 



