492 
ME. J. NORMAN LOCKYER ON SPECTRUM-ANALYSIS. 
Such spectra, like those of the metalloids, are separated spectroscopically from those 
of the metallic elements by their columnar or handed structure. 
IV. There are, in all probability, no compounds ordinarily present in the sun’s reversing 
layer. 
V. When a metallic compound vapour, such as is referred to in III., is dissociated by 
the spark, the band spectrum dies out, and the elemental lines come in, according to the 
degree of temperature employed. 
Again, although our knowledge of the spectra of stars is lamentably incomplete, I 
gather the following facts from the work already accomplished with marvellous skill and 
industry by Secchi of Eome. 
VI. The sun, so far as the spectrum goes, may be regarded as a representative of 
class ((3) intermediate between stars (a) with much simpler spectra of the same kind and 
stars (y) with much more complex spectra of a different kind. 
VII. Sirius, as a type of a, is (1) the brightest (and therefore hottest 1 ?) star in our 
northern sky ; (2) the blue end of its spectrum is open ; it is only certainly known to 
contain hydrogen, the other metallic lines being exceedingly thin, thus indicating a 
small proportion of metallic vapours; while (3) the hydrogen lines in this star are enor- 
mously distended, showing that the chromosphere is largely composed of that element. 
There are other bright stars of this class. 
VIII. As types of y the red stars may be quoted, the spectra of which are composed 
of channelled spaces and bands, and in which naturally the blue end is closed. Hence 
the reversing layers of these stars probably contain metalloids, or compounds, or both, 
in great quantity ; and in their spectra not only is hydrogen absent, but the metallic 
lines are reduced in thickness and intensity, which in the light of V., ante, may indicate 
that the metallic vapours are being associated. It is fair to assume that these stars are 
of a lower temperature than our sun. 
I have asked myself whether all the above facts cannot be grouped together in a 
working hypothesis which assumes that in the reversing layers of the sun and stars 
various degrees of “ celestial dissociation” are at work, which dissociation prevents the 
coming together of the atoms which, at the temperature of the earth and at all artificial 
temperatures yet attained here, compose the metals, the metalloids, and compounds. 
On this working hypothesis, the so-called elements not present in the reversing layer 
of a star will be in course of formation in the coronal atmosphere and in course of 
destruction as their vapour-densities carry them down ; and their absorption will not 
only be small in consequence of the reduced pressure of that region, but what absorp- 
tion there is will probably be limited wholly or in great part to the invisible violet end 
of the spectrum in the case of such bodies as the pure gases and their combinations and 
chlorine (see I. ante). 
The spectroscopic evidence as to what may be called the plasticity of the molecules 
of the metalloids, including of course oxygen and nitrogen, but excluding hydrogen, is 
so overwhelming, that even the absorption of iodine, although generally it is transparent 
