PRESENT PROBLEMS OF METEOROLOGY 747 



carriers of electricity has thrown some light on this question. 1 It 

 is of importance in geophysics to know how the capacity of the air 

 for positive and negative electrons varies with altitude, to learn 

 the periodic and non-periodic variation of the potential at the earth's 

 surface and the law of dissipation of electricity. 



Attempts to regard all atmospheric phenomena as periodic and 

 due to the influence of the sun or moon have long occupied the 

 attention of eminent investigators, but it must be admitted that 

 the effects of neither the periods of solar nor of lunar rotation 

 upon the earth's meteorology can be claimed to have been proved, 

 although a correspondence has been found by the distinguished 

 speaker who preceded me in regard to the frequencies of auroras 

 and thunder-storms and the position of the moon in declination. 2 

 To Professor Arrhenius is also due the remarkable generalization 

 that the pressure of light emanating from the sun causes alike the 

 streaming-away from it of comets' tails, the zodiacal light, and 

 the aurora borealis. The relation of sun-spot frequency, which has 

 a periodicity of about eleven years, to atmospheric changes on the 

 earth, especially as manifested by barometric pressure, rainfall, and 

 temperature in India, has been investigated, and the coincidences, 

 even if nothing more, which have been shown to exist by Sir Norman 

 Lockyer and his son are suggestive. 3 It may be pointed out that the 

 same action of the sun might cause simultaneously increased rain- 

 fall in India and a deficiency of rainfall in England, because rising 

 currents in one region are necessarily accompanied by descending 

 currents elsewhere, and, therefore, no objection can be offered to a 

 theory of cosmical influence which produces different weather con- 

 ditions in different parts of the globe. 



Since the sun is the source of our energy, the discovery of any 

 variation in the heat emitted is of the deepest interest, and the 

 important investigations of Professor Langley 4 are now to be sup- 

 plemented by the broader work of a committee appointed by the 

 National Academy of Sciences 5 and also by an international com- 

 mission, 9 with the general object of combining and discussing meteor- 

 ological observations from the point of view of their relation to 

 solar phenomena. It does not seem improbable, therefore, that 

 eventually we may have seasonal predictions of weather possessing 

 at least the success of those now made daily, and that possibly 

 forecasts of the weather will be hazarded several years in advance. 

 The value of such forecasts, as affecting the crops alone, would be 



1 Terrestrial Magnetism and Atmospheric Electricity, vo\.\i, pp. 9-10. 



2 Arrhenius, Lehrbuch der Kosmischen Physik, pp. 791, 



3 Nature, vol. LXIX, pp. 351-357. 



4 Report of Secretary of Smithsonian Institution, It 03, pp. 2.6, 78- 

 6 Science, N. S., vol. xx, pp. 316, 930-932 



Quarterly Journal of Royal Meteorological Society, vol. xxxi, p. ^ 



