32 EEPORT — 1882. 



These investigations Sssume additional importance wten we vidW 

 them in connection with solar — I may even say stellar — physics, for evi- 

 dence is augmenting in favour of the view that interstellar space is not 

 empty, but is filled with highly attenuated matter of a nature such as 

 may be put into our vacuum tubes. Nor can the matter occupying 

 stellar space be said any longer to be beyond our reach for chemical and 

 physical test. The spectroscope has already thrown a flood of light upon 

 the chemical constitution and physical condition of the sun, the stars, the 

 comets, and the far distant nebulte, which latter have yielded spectro- 

 scopic photographs under the skilful management of Dr. Huggins, and 

 Dr. Draper of New York. Armed with greatly improved apparatus the 

 physical astronomer has been able to reap a rich harvest of scientific 

 information during the short periods of the last two solar eclipses ; that 

 of 1879, visible in America, and that of May last, observed in Egypt 

 by Lockyer, Schuster, and by Continental observers of high standing. 

 The result of this last eclijjsc expedition has been summed up as follows : 

 * Different temperature levels have been discovered in the solar atmo- 

 sphere ; the constitution of the corona has now the possibility of being 

 determined, and it is proved to shine with its own light. A suspicion 

 has been aroused once more as to the existence of a lunar atmosphere, 

 and the position of an important line has been discovered. Hydro-carbons 

 do not exist close to the sun, but may in space between us and it.' 



To me personally these reported results possess peculiar interest, for 

 in March last I ventured to bring before the Royal Society a speculation 

 regarding the conservation of solar energy, which was based upon the 

 three following postulates, viz. : — 



1. That aqueous vapour and carbon compounds are present in stellar 

 or interplanetary space. 



2. That these gaseous compounds are capable of being dissociated by 

 radiant solar energy while in a state of extreme attenuation. 



3. That the effect of solar rotation is to draw in dissociated vapours 

 upon the polar surfaces, and to eject them after combustion back into 

 space equatorially. 



It is therefore a matter of peculiar gratification to me that the results 

 of observation here recorded give considerable support to that speculation. 

 The luminous equatorial extensions of the sun which the American ob- 

 servations revealed in such a striking manner (with which I was not 

 acquainted when writing my paper) were absent in Egypt; bat the 

 outflowing equatorial streams (I suppose to exist) could only be rendered 

 visible by reflected sunlight, or by electric discharge when mixed with 

 dust produced by exceptional solar disturbances; and the occasional 

 appearance of such luminous extensions would serve only to disprove 

 the hypothesis entertained by some, that they are divided planetary 

 matter, in which case their appearance should be permanent. Professor 

 Langley, of Pittsburg, has shown by means of his bolometer, that the 

 solar actinic rays are absorbed chiefly in the solar instead of in the 



