METEOROLOGY AND ALLIED SUBJECTS. 



281 



of barometric maxima are reinforced when over the laud as compared 

 with the sea. He traces the nightly flow of cool air down mountaiu 

 slopes aud its accumulation in valleys, its warming by comi)ressiou and 

 by formation of dew, its cooling by radiation, and its. contraction by 

 cx)oling, and deduces the resulting influence of all this upon the diurnal 

 fluctuations of barometric pressure. {Z. 0. G. M., Vol. XVI, 1881, p. 94.) 

 Supan, in an extensive memoir on the annual variations of heat on the 

 earth's surface, says: In general the annual variation increases from the 

 equator towards the poles, and from the coast line towards the interior. 

 If we determine the mean annual variability for the different latitudes, 

 we find the following values : 



Latitude. Annual variability. 

 TOO j^. 35.6 



60O N. 31.1 



50 :N^. 25.4 



40' N. 19.2 



30 :N'. 12.4 



20 N. 8.4 



1.0 3.7 



.0 1.3 



10° S. 2.9 



20O S. 6.0 



30O 8.1 



40O 8.8 



{Z. O. G. M., Vol. XVI, 1881, p. 38.) 

 Pernter has studied the distribution of sunshine as recorded since 

 April, 1880, by means of the sunshine-recorder invented by Campbell, 

 and consisting of a glass lens, by means of which the concentrated sun's 

 rays fall upon and burn into a pai)er strip. On account of the import- 

 ance of a better knowledge of the duration of sunshine, it is to be hoped 

 that similar cheai) and simple registers shall bo kept at numerous sta- 

 tions throughout the world. The following table shows the diurnal 

 variability : 



{Z. 0. G. If., Vol. XVI, 1881, p. 9.) 



VI. — MOISTUEB, CLOUDS, RAIN, ETC. 



The connection between rainfalls and solar spots has been further 

 elucidated by Meldrum, who has computed new values of the averages 

 in order to meet the objections that have been raised against this pre- 



