140 Transactions of tlic South African Philosophical Society. 



computed, April shows a distinct triple maximum, at II., X., and 

 XVII. ; July also at VI. and XIV., with an abortive maximum at XX. ; 

 January at VII. and XV., with a suspicion of a maximum curvature 

 about I., while October has distinctly no trace of more than the two, 

 at III. and XVIII. April and October combined give maxima at a 

 little before III., between X. and XI., and between XVII. and 

 XVIII. These, however, are partially eliminated by the maximum 

 and minimum points of January and July. The Trevandrum ob- 

 servations indicate a triple maximum pretty clearly at XI., XVII., 

 and midnight, but the other Indian stations seem to show but 

 two. 



Upon the whole the outside evidence lends some colour to the 

 idea that the successive crests of the cloud-waves approximate at 

 Kimberley to the time whose distance from a fixed origin is some 

 multiple of eight hours, and thus operate to the full upon the third 

 periodic term of the Bessel-formula for temperature. Against this, 

 however, may be set the opinion of Eliot : " The curves giving the 

 diurnal variation of cloud [in India] differ entirely from those of 

 temperature and air-movement. ... As might further be expected, 

 the Besselian resolution of the diurnal variation of cloud differs 

 entirely from the corresponding resolution of the air-pressure velocity 

 and temperature. The relation of the amplitudes and the epochs 

 differ so widely and irregularly as to show there is no direct relation 

 between the corresponding elements of the resolution of cloud and 

 those of the other elements named above." '" 



This opinion notwithstanding, a comparison between the harmonic 

 constants of cloud and temperature at Trevandrum furnishes food for 

 reflection. For the nine years, 1856-1864, counting from midnight, 

 they are : — f 



Temperature. Cloud. 



V, 240° 6' 232° 4' 



V, 82 46 258 43 



V3 23 41 43 15 



V4 244 28 127 5 



u, 5-101 0-551 



u^ 1-354 0-123 



u, 0-376 0-222 



u, 0-295 0-162 



* Indian Met. Memoirs, vol. xii., part 2, pp. 196-7. 

 f Indian Met. Memoirs, vol. x., part 1, pp. 22 and 135. 



