TKkKi:STKlAI. I'lUSICS. ^i,' 



l)heiii)niena. As early as kjck; a theory of ihe origin of the 

 colour of the sky was athanced, and accordins^ to it. selective 

 reflection must lake i)lace in the upper atmosi)here, the s])ectra of 

 the reflected lii^^lit havini^ a inaxininm intensitx in the nei^h])our- 

 hood of H. 



Nicholson lias actually observed an emission line under cer- 

 tain conditions. ( )ur observations U]) to the ))resent ha\e not vet 

 conflrmed this result. 



Prof. A. Brou x : The thanks of the Section and of the 

 Association are due to Trof. Morrison for his intere-^ling and 

 timely pai)er. He did well to point out the peculiar -^uitabilil)- 

 of South Africa for work on solar radiation. A point of prac- 

 tical im]>ortance in thi> connection is that the work could natur- 

 ally be co-ordinated with the problem of obtainint^- i)ower direci 

 from the sun's radiant enerij}'. ( )nly a ((ualihed success has 

 attended efl'orts \n other countries, and the problem i< rejs^arded 

 rather as one for tlie futin-c, when the inaccessil)ilitv of fuel 

 reserves may make the use oit sim-|Kiwer a soimder economii- 

 proposition. It i> a matter for investigation whether even now 

 this source t)f ]jower might not be protitabK- tai)]ied in i)arts of 

 Africa, where fuel is not easil\" a\ailable and sunlight is intense 

 and Continuous.* 



Meteorology is always with us; and so far the ])ractical 

 results of the science have been disa])|)ointing. The farmer stil! 

 asks in vain for a reasonal)le forecast of the date of beginning 

 and the time-distril)Ution of the .seasonal rains. A difference of 

 three weeks in the date of commencement uiay rtiin a croj) — cj/., 

 oi mealies — whereas a rough previous knowledge of the date 

 would enable the farmer to adjust his time of sowing so as to get 

 the full benefit of rain available. There are striking local dif- 

 ferences of distril)Ution in areas nearly contiguous, and the 

 collection and examination of data for a limited district might 

 lead to ])ractical conclusions. 



The (|uestions of e\ ajjoration and percolation as leading to 

 loss of im]jounded water are already receiving atteiuion.t 



The field of geo])hvsics suggests wide possibilities. The 

 work of Sutton should be meutioned in connection with small 

 motions of the earth's crust. Some work also has been done on 

 earthquakes, and in certain places in South Africa seismological 

 records are avai]al)le. Some interesting (juestions arise out of 

 Prof. .\. Young's in\ estigations into tidal phenomena in luider- 

 ground water. J A jxissible ex))lanation is the yielding of the 

 earth's crust under the pressure of ocean tides, accompanied In 

 the s(|ueezing out of underground water where it has access to 



* Intiham. Presidential Address. Proc. S.A. Inst, of /iin/iiiccrs. Aug., 



1915- 



t A. D Lewis: "Run ot'f and Reservoir losses at Van Wyk's Vlei." — 

 Proc. S.A. Soc. C.E. (1915), 5. A. H. Hallis : "Railway water supplies, 

 with special reference to Vryburg-Bulawayo Section." I'roc. S..I. .Soc. 

 C.i/:.\ (igi6). 206. 



tTraiis. R.S. S. .Ifrici-. ( 191,1 ». 3 li], Oi. 



