118 Transactions of the South African Philosophical Society. 



on the whole, landwards by day during the summer, and even more 

 considerably seawards by night during the winter. Is it hazarding 

 too sweeping a suggestion that the energy of this movement may be 

 propagated in some form up to at least such a limit as is defined 

 by the condition — 



«! [max.] — fti [min.] ? 



If so, we have a glimmering of the possible explanation of the 

 intrusion of easterly winds at Kimberley somewhat earlier at night 

 than would be the case if the vane followed the sun's diurnal march 

 with uniform angular velocity.''' For the lower air-strata trending 

 seawards at night must be replaced in great part by air from above. 

 Now because of the much higher temperature of the sea-surface 

 along the eastern coast than upon the western, the greater air- 

 transfer of the two will take place across the eastern littoral, and 

 hence such air as may be supposed to settle down into the depleted 

 space inland, at night, must have in the long run a pronounced 

 easterly component. A little consideration will make it clear, 

 moreover, that it could only appear very plainly beyond — and 

 perhaps not far beyond — the area over which the influence of 

 the sea upon the temperatures was felt. For all of the inflowing 

 upper current that settled down upon, coming into actual contact 

 with, the outflowing lower current must, of course, have its flight 

 modified by friction, and either be retarded, or brought to rest, or 

 turned aside, or even forced into the lower drift, according to cir- 

 cumstances. The momentum of such portion of the mass as had 

 not been checked carrying it beyond the limits of outflowing 

 air, it would here impress its own velocity, westwards, most 

 strongly upon the air remaining. Thus, upon this view, the 

 winds in question mark a sort of backwash to the diurnal pen- 

 dulum-like swiug of the air at right angles to the coast-line. As 

 a further argument upon the same side it may be mentioned that 

 winds with an easterly component seem to be more frequent over 

 Kimberley in winter than in summer between the hours of XX. and 

 midnight. 



Now it has been shown in the paper two or three times men- 

 tioned that the maximum temperatures day by day at Kimberley 

 appreciably satisfy the equation — • 



a = AS^cosZ -f B (1) 



* Some further information is now being prepared bearing upon this curious 

 circumstance. 



