Diurnal Meteorological Conditions at Kimherley. 157 



falling temperature inland, and still more by the land-breeze, the 

 process going on until the upper current has set in with sufficient 

 strength to establish a return to equilibrium. During the day, on 

 the other hand, the conditions are reversed, and the sea-breeze 

 tends to fill up the partial void of the afternoon minimum. There 

 are other agencies in operation, doubtless ; nevertheless, the most 

 pronounced features of the pressure-curves of stations on an ocean 

 littoral are more largely dynamical than any others/'' 



The winds of Kimherley have been previously treated at some 

 length,! so that it will not be necessary here to do more than discuss 

 just so much of this division of the subject as comes within present 

 limits. In Table 31 will be found — 



1. The total hours of wind from each given direction upon clear 

 days in each month during the four years 1898-1901. 



2. The total hours of wind from each given direction upon clear 

 days, cloudy days, and all days, during the same four years ; and 

 also — 



8. The ratios of each per 10,000. 



4. The gross total hours from each direction during the period 

 March, 1896 (when hourly observations of wind were commenced)- 

 February, 1902, i.e., six years. 



Tables 32, 33, 34, give the hourly distribution according to direc- 

 tion, during the four years, upon clear days, cloudy days, and all 

 days. From these Table 35 has been deduced. It gives the magni- 

 tude of the N. and E. component directions, decimal parts being 

 omitted, found in the same manner as a mechanical component ; the 

 resultant direction E ; and the vectorial angle (measured from E. 

 round by N., W., and S.) made by R. 



The east component is very little affected, whether the sky be 

 clear or cloudy. It changes from |j)Zzts to minus sign (i.e., becomes 

 W.) a full hour earlier ; and from minus to plus {i.e., becomes E. 

 again) perhaps half an hour earlier when the sky is cloudy than 



* [Upon the whole question of the double diurnal oscillation of the barometer, 

 a great store of valuable information will be found in Eliot's "Discussion of the 

 Kesults of the Hourly Observations Kecorded at 29 Stations in India," in the Indian 

 Met. Memoirs, vol. xii., part 3, recently published. Eliot claims that the diurnal 

 variations of pressure are chiefly due to the absorption of solar energy by our 

 atmosphere. But to my mind the argument is not convincing. It seems to 

 confuse the issue between the amount of absorption suffered by any given solar ray, 

 and the amount effected by any given mass of air. The former has a maximum at 

 sunrise or sunset ; the latter at noon. (Note added in reading the proof, Feb. , 

 1903.)] 



t Transactions of the S. A. Phil. Soc, vol. xi., part 1. Met. Zeitschrift, 

 Nov., 1901. 



