6L6 



SCIENCE. 



[N. S. Vol. XVII I. No. 403. 



By this time spectroscopic observations 

 of the solar changes had proved that the 

 sun was hottest when there were most spots, 

 thereby upsetting the old idea that the spots 

 acted as screens and reduced the radiation 

 at sun-spot maximiun. Koppen's result, 

 therefore, was a paradox, and was thus ex- 

 plained by Blanford.* 



The temperatures dealt with by Professor Kop- 

 pen are of course those of the lowest stratum of 

 the atmosphere at land stations, and must be 

 determined not by the quantity of heat that falls 

 on the exterior of the planet, hut on that lohich 

 penetrates to the earth's surface, chiefly to the land 

 surface of the globe. The greater part of the 

 earth's surface being, however, one of water, the 

 principal immediate effect of the increased heat 

 must be the increase of evaporation, and there- 

 fore, as a subsequent process, the cloud and the 

 rainfall. Now a cloudy atmosphere intercepts 

 the greater part of the solar heat, and the re- 

 evaporation of the fallen rain lowers the tem- 

 perature of the surface from which it evaporates 

 and that of the stratum of air in contact with it. 

 The heat liberated by cloud condensation doubt- 

 less raises the temperature of the air at the 

 altitude of the cloudy stratum; but at the same 

 time we have two causes at work, equally tending 

 to depress that of the lowest stratum. As a con- 

 sequence, an increased formation of vapor, and 

 therefore of rain, following on an increase of 

 radiation, might be expected to coincide with a 

 low air-temperature on the surface of the land.f 



The next important advance had to do 

 with atmospheric pressure. In 1875, Mr. 

 C. Chambers, the director of the Bombay 

 Observatory, found that 



Tlie variation of the yearly mean barometric 

 pressure at Bombay shows a periodicity nearly 

 corresponding in duration with the decennial sun- 

 spot period.t 



The years round 1875 were rendered very 

 important by the number of new organiza- 

 tions established to record and demonstrate 

 various classes of observations with which 



* Blanford, Bengal, Asiat. Soc. Journ., 1875. 



fSee also Blanford, Nature, April 23, 1891, 

 Vol. 43, p. 583. 



J ' Meteorology,' Bombay Presidency, August, 

 1875, S. 26, p. 12. 



we are concerned in this short history. 

 Meteorological enquiries on a large scale 

 were organized at home and in India, and 

 observatories were established at Potsdam, 

 Paris and London, with the main object of 

 studying solar changes. At the same time 

 steps were taken to resume observations in 

 the tropics. It is not out of place here to 

 make a brief reference to what was done 

 in Britain and India. 



The government took this action in con- 

 sequence of ■ a strong recommendation of 

 the Royal Conunission on Science, presided 

 over by the late Duke of Devonshire, of the 

 establishment by the state of an Observa- 

 tory of Solar Physics in which enquiries 

 relating to the nature of the sun and its 

 changes should be fostered and various 

 investigations which were necessary should 

 be carried on. 



The commission also proposed that sim- 

 ilar institutions should be established in 

 various parts of the empire. 



The ground on which the Royal Commis- 

 sion, and subsequently a memorial pre- 

 sented to the government by the British 

 Association, urged this new departure was 

 that, in the opinion of a considerable num- 

 ber of scientific men, there was a more or 

 less intimate connection between the state 

 of the sun's surface and the meteorology 

 of the earth; and they called attention to 

 the fact that recent independent investiga- 

 tions on the part of several persons had led 

 them to the conclusion that there was a 

 similarity between the sun-spot period, 

 periods of famine in India, and cyclones 

 in the Indian Ocean. The memorialists 

 concluded by saying: 



We remind your lordships that this important 

 and practical scientific question can not be set 

 definitely at rest without the aid of some such in- 

 stitution as that the establishment of which we 

 now urge. 



The Lords of the Committee of Council 

 on Education referred this memorial to a 



