XKAMSiACTIONJ! OF SKCHON A. 459 



of a definite periodicity in the occurrence of hailstorms. It might, moreover, be 

 reasonably doubted whether the attraction of such small bodies was sutHcieni to 

 prevent their disappearance by evaporation, supposing them to be capable of exist- 

 ing outside the atmosphere of the earth. 



4. Second Beport of the Committee on Meteoric Bust. — See Reports, p. 90. 



5. Sun Light and SJcy Light at High Altitudes. By Captain W. de W. 



Abney, F.E.S. 



The author called attention to the fact that photographs taken at high altitudes 

 show skies that are nearly black by comparison with bright objects projected against 

 them ; and he went on to show that the higher above the sea-level the observer 

 went, the darker the sky really is, and the fainter the spectrum. In fact, the latter 

 shows but little more than a band in the violet and ultra-violet at a height of 

 8,500 feet, whilst at sea-level it shows nearly the whole photographic spectrum. 

 The only reason of these must be particles of some reflecting matter from which 

 sunlight is reflected. The author traces this to watery stuft' of which nine-tenths 

 is left behind at the altitude at which he worked. He then showed that the bright- 

 ness of the ultra-violet of direct sunlight increased enormously the higher the 

 observer went, but only to a point, for the spectrum suddenly terminated at about 

 2,940 wave-lengths. This abrupt absorption was due to extra-atmospheric causes, 

 and perhaps to space. The increase in brightness of the ultra-violet was such that 

 the usually invisible rays L, M, and N could be distinctly seen, showing that the 

 visibility of these rays depended on the intensity of the radiation. The red and 

 ultra-red part of the spectrum was also considered. He showed that the absorption 

 lines were present in undiminished force and numbers at this high altitude, thus 

 placing their origin to extra-atmospheric causes. The B and A line he also stated 

 could not be indubitably claimed as telluric lines, but might originate between the 

 sun and our atmosphere, as they were as strong at the zenith as at the horizon 

 at this altitude. The author confirmed the presence of derivative benzine and 

 ethyl in the same region. He had found their presence indicated in the spectrum 

 at ,sea-level, and found their absorption lines with undiminished intensity at 8,500 

 feet. Thus, without much doubt, hydrocarbon must exist between our atmosphere 

 and the sun, and, it may be, in space. 



6. On the Distrihution of Energy in the Solar Spectrum. 

 By Professor S. P. Langlet. 



Of the Avhole solar energy nearly three-fourths, according to the author's 

 measures, exists in the invisible portion below the red, yet of this great region very 

 little is known, and of its extent upon the wave-length scale we are hitherto nearly 

 ignorant. This ignorance arises from ditficulties of research due to the compression 

 of the infra-red end by the prism, and to the absence of means for separating and 

 distinguishing individual rays in this crowded portion, or of determining their wave- 

 length, since no law of connection between wave-lengths and indices of refraction 

 can be said to be known. 



The object of this communication is to present a map of the energy in this 

 infra-red portion throughout its entire length, both on the prismatic and wave- 

 length scale. 



These charts {e.r/nbited) show the distribution of the solar energy through this 

 hitherto little known region, both on the wave-length and on the pi-ismatic scale. 

 The measm-es have been made by means of the linear balometer {exhibited) , and 

 the wave-lengths determined by one of the new concave gratings devised by 

 Professor Rowland (exhibited). The energies are proportional to the ordinates, 

 and the approximate wave-length of each ray is given. 



