CELESTIAL CHEMISTRY. 371 



the same series of lines as those of hehum in the sun. HeHum 

 had, in fact, at length been found on this earth. 



Since then Sir William Ramsay has shown that helium is a 

 disintegration product of radium : that is to say, radium, 

 breaking up spontaneously, produces helium, and in so doing' 

 gives forth a colossal amount of heat. In that case the enormous 

 quantities of helium in the sun argue for the existence in the 

 past, and possibly also at present, of large supplies of radium 

 in the sun's substance, and this would go very far to account 

 for the continuance of the solar lieat through countless ages, 

 past and future. 



Out from the chromosphere of the sun, beyond the regions 

 of its visible atmosphere, huge reddish prominences, or ejections, 

 of faintly luminous teaming gas are continually being belched 

 forth. On account of the intensely brilliant light emitted by 

 the body of the sun itself, these protuberances are practically 

 invisible except during a total eclipse. In a photopraph of the 

 sun during the total eclipse of the 7th August, 1869, four red 

 prominences may be distinctly observed protruding behind 

 the dark body of the moon. The immense size 

 of the solar prominences can be best gauged by comparing- 

 one of them, observed by Prof. Fenyi in Hungary, on the 3rd 

 October, 1892, with the size of the earth drawn to scale. 1 his 

 particular prominence extended to a height of 237.000 miles 

 above the sun's surface. 



These prominences — these vast just of flame, as they in 

 reality are — when the spectroscope is turned towards them do 

 not exhibit continuous spectra, but spectra of bright lines, a 

 circumstance which indisputably proves that they are not 

 incandescent solids like the inner nucleus or photosphere of the 

 sun, but glowing gases. This, in fact, holds good not alone 

 for the prominences, but for the entire chromosphere. When 

 the chromosphere w'as first examined through the spectroscope, 

 in 1868, by Dr. Janssen. a yellow line, supposed to be that of 

 sodium, was observed; it has since been found to be that of 

 helium. When looking at the spectra of sodium and helium one 

 notices how nearly identical are the positions occupied by the 

 yellow helium line and that of sodium. And the enormous 

 tongues of flame — hundreds of thousands of miles long — were 

 found by Sir Norman Lockyer to consist of ignited masses of 

 gas, principally hydrogen. But they have also been found to 

 contain great quantities of calcium vapour, and this discovery 

 has been made in a most remarkable way. Let me revert back 

 a little in order to explain. If the sun were simply a ball of 

 incandescent solid or liquid, unsurrounded by any gas or 

 vapour, its spectrum would be absolutely continuous — that is to 

 say, no dark lines would be visible in it. The atmosphere which 

 surrounds the sun is highly charged with metallic vapours, and 

 these vapours all absorb light from the innermost nucleus, and 

 reveal their presence by their respective dark lines in the 

 spectrum. This atmosphere of the sun accordingly acts as a 

 reversing" layer. Of course it is, as has already been said, 

 intensely hot, but it is cool in comparison with the glowing mass 

 within, and into this cooler atmosphere are projected eruptions of 



