622 



SCIENCE. 



[N. S. Vol. XVIII. No. 463. 



that the famines which have devastated 

 India during the last half century have 

 oceurjed in the intervals between the 

 pulses. 



In 1902, with a view of getting more 

 light on the important issues raised by the 

 comparison of the solar heat pulses and the 

 Indian rainfall, I determined to reduce the 

 observations of prominences made by Tac- 

 chini at the Observatory of the CoUegio 

 Eomano since 1874, and compare the Indian 

 meteorological conditions with them. The 

 reason for this step was that the admirable 

 photographs of the prominences on the 

 solar disc, published by Hale and Deslan- 

 dres, showed the extensive area over which 

 they were distributed. An argument which 

 has been used against the possible connec- 

 tion between solar and terrestrial changes 

 was based upon the small area covered by 

 spots. In 1877 Eliot wrote as follows:* 



So far as can be judged from the magnitude of 

 the sun spots, the cyclical variation of the magni- 

 tude of the sun's face free from spots is very 

 small compared with the surface itself ; and con- 

 sequently, according to mathematical principle, 

 the effect on the elements of meteorological ob- 

 servations for the whole earth ought to be small. 



Now the photographs, to which I have 

 referred, exhibited broad bands of prom- 

 inences extending almost across the whole 

 disc, and if we assume two belts of prom- 

 inences, N. and S., 10° wide, with their 

 centers over latitude 16°, a sixth of the 

 sun's hemisphere would be in a state of 

 disturbance. Hence it followed that the 

 prominence effect, when fully studied, 

 might be much more striking and impor- 

 tant than that produced by spots. 



The prior work in connection with the 

 Indian rainfall had shown not only that 

 there was a close connection between pres- 

 sure and rainfall, but that the pressure 

 was much the more constant element over 

 the different 'areas. The comparison with 



* * Report on the Meteorology of India,' 1877, 



p; 2. ■ 



the prominences obtained from the discus- 

 sion of Tacchini's results was in the first 

 instance compared with the Indian pressure 

 curve. 



~ The result was magnificent. In addi- 

 tion to the well-marked prominence maxi- 

 mum at the maximum of the spotted area, 

 there were others corresponding approxi- 

 mately with the 'crossings' of the widened 

 lines, and all were re-echoed by the Indian 

 barometers ! 



The sun-spot cycle of eleven years gave 

 way to a prominence cycle of about 3.7 

 years, and by this interval, as a rule, are 

 the Indian pressures separated. 



To see whether such a striking and im- 

 portant result as this was limited to Indian 

 ground, the magnificent series of pressure 

 obtained at Cordoba in South America were 

 studied. Here the same effect was also 

 most marked, but with the important dif- 

 ference that the curves were inverted ; that 

 is, high pressure years in India were repre- 

 sented by low pressure years in Cordoba. 

 In order to extend the Indian and Cordoba 

 areas and see how far these conditions pre- 

 vailed, the pressure variations of stations 

 as widely distributed as possible were ex- 

 amined. The result of this inquiry showed 

 that the world might be divided roughly 

 into two portions. The Indian area was 

 found to extend to Australia, East Indies, 

 Asiatic Eussia, Mauritius, Egypt, East 

 Africa and Europe, while the Cordoba re- 

 gion might be said to include not only South 

 and Central America, but the United States 

 and Canada, extending further west than 

 Honolulu. 



This discovery of this barometric surge, 

 which has been corroborated since by Pro- 

 fessor Bigelow, was an important advance, 

 and will enable the investigator to connect 

 up regions that undergo similar pres.sure 

 changes. 



In addition to the two periods, namely, 

 11 and 3.7 years, mentioned above, Briick- 



