1888.] of the various Species of Heavenly Bodies. 63 



being the brightest (fig. 14). The lines, flutings, or bands in 

 the lowest horizon, in the case of each element, are those seen at 

 the lowest temperatures, and are the first to appear when only 

 a small quantity of substance is present. Those in the upper 

 horizons are .the faintest, and are only seen when the tempera- 

 ture is increased, or a considerable amount of the substance is 

 volatilised. The map shows that if there are any indications of 

 magnesium, for instance, in bodies at low temperatures, the fluting 

 at 500 will be seen, possibly without the other fluting or lines. The 

 first indications of manganese will be the fluting at 558, and so on. 

 Again, on account of the masking effect of the spectrum of one element 

 upon that of another, we may sometimes have an element indicated in 

 a star spectrum, not by the brightest band or fluting in its spectrum, 

 but by the second or even third in brightness ; this, of course, only 

 occurs when the darkest band falls on one of the brightest flutings of 

 carbon, or upon a dark band in the spectrum of some other element. 

 In the former case the dark band will be cancelled or masked ; in the 

 latter case the two absorptions will be added together, and form a 

 darker band of a different shape. 



The Question of Mashing. 



If we consider the masking effects of the bright carbon flutings 

 upon the absorption spectrum of each of the elements which, accord- 

 ing to the results obtained, enter into the formation of Duner's bands, 

 we have the following as the main results : — 



Magnesium. — There are two flutings of magnesium to be considered, 

 the brightest at 500 and the other at 521. In the earlier stages of 

 Duner's stars only the fainter one at 521 is visible, but the absence 

 of the brightest at 500 is accounted for by the masking effect of the 

 bright carbon fluting starting at 517. As the carbon fades, the 517 

 fluting narrows and the absorption of magnesium 500 becomes 

 evident. 



Manganese. — The two chief flutings of manganese are at 558 and 

 586, the former being the brightest fluting in the spectrum. The 

 second fluting is seen in all of Duner's stars. The first fluting, 558, 

 however, does not appear as an absorption fluting until the radiation 

 fluting of carbon starting at 564 has narrowed sufficiently to unmask 

 it. It is thus easy to understand why, in some stars, there should be 

 the second fluting of manganese without the first. 



Barium. — The spectrum of barium consists of a set of flutings ex- 

 tending the whole length of the spectrum, and standing out on this 

 as a background are three bright bands ; the brightest band is at 

 515, the second is at 525, and the third, a broader band, is about 485. 

 The second band is recorded as an absorption band in Duner's stars, 

 the apparent absence of the first band being due to the masking 



