Miscellaneom. 227 



an alcoliol flame a spectrum having tliree intense green lines very 

 near together. Let now the alcohol flame be illuminated by the 

 incomparably more vivid oxy-calcium light, and the spectrum 

 before feeble is greatly enhanced in brilliancy, all the light from 

 the latter source, except that corresponding to the three green 

 lines, freely penetrating the flame. It follows that though these 

 green lines are absohitely illuminated as much as at first, yet 

 being relatively illuminated much less they appear as three lines 

 of shadow across the spectrum. It will be apprehended that what 

 has here for distinctness' sake been said of the magnesium spec- 

 trum and of three lines in it only, applies equally well to all spec- 

 tra with all their luminous lines. Here then as KirchofF intimates, 

 is the explanation of the apparent paradox that while light from all 

 artificial sources is characterized by bright lines, the solar spec- 

 trum, as first pointed out by WoUaston and Fraunhofer, is marked 

 by numerous dark lines. It is in fact a negative spectrum. In 

 the words of that author; "the sun possesses an incandescent 

 gaseous atmosphere which surrounds a solid nucleus having a still 

 higher temperature. If we could see the spectrum of the solar 

 atmosphere, we should see in it the bright bands characteristic of 

 the metals contained in the atmosphere. The more intense lu- 

 minosity of the sun's solid body, however, does not permit the 

 spectrum of its atmosphere to appear; it reverses it ; so that in- 

 stead of the bright lines which the spectrum of the atmosphere by 

 itself would shew dark lines are produced." With these fects 

 in view we are prepared to learn that the attempt has been made, 

 not wholly unsuccessful, though yet incomplete, to analyze the 

 solar atmosphere. The mode of procedure is intelligible enough. 

 Two spectra in close proximity — the one, that of the sun — the 

 other, that of any metal in the electric spark — are viewed simul- 

 taneously in the same telescope. If all the bright lines of the 

 latter correspond exactly to certain of the dark lines in the former, 

 it seems a warrantable conclusion that that metal is present in 

 the incandescent solar atmosphere. If this exact correspondence 

 is wanting it may be similarly affirmed that that metal is present, 

 if present at all, in comparatively minute quantities. On such 

 grounds Kirchofif asserts that the solar atmosphere certainly con>- 

 tains Iron, Chromium, Nickel and Magnesium, while if Silver, 

 Copper, Zinc, Aluminum, Cobalt and Antimony are present they 

 are in such small relative proportion as to fail to give any evi- 

 dence of their presence in the spectrum, 



S. p. R. 



