156 ON THE ORIGIN OF THE PLANETARY SYSTEM. 



over, how our figs. 7, 8, and 9 indicate iron, calcium, 

 and sodium, and also the presence of hydrogen, of zinc, 

 of copper, and of the metals of magnesia, alumina, 

 baryta, and other terrestrial elements. Lead, on the 

 other hand, is wanting, as well as gold, silver, mercury, 

 antimony, arsenic, and some others. 



The spectra of several fixed stars are similarly con- 

 stituted ; they show systems of fine lines which can be 

 identified with those of terrestrial elements. In the 

 atmosphere of Aldebaran in Taurus there is, again, 

 hydrogen, iron, magnesium, calcium, sodium, and also 

 mercury, antimony, and bismuth ; and, according to 

 II. C. Vogel, there is in a Orionis the rare metal 

 thallium ; and so on. 



We cannot, indeed, say that we have explained all 

 spectra; many fixed stars exhibit peculiarly banded 

 spectra, probably belonging to gases whose molecules 

 have not been completely resolved into their atoms by 

 the high temperature. In the spectrum of the sun, 

 also, are many lines which we cannot identify with 

 those of terrestrial elements. It is possible that they 

 may be due ty) substances unknown to us, it is also 

 possible that they are produced by the excessively high 

 temperature of the sun, far transcending anything we 

 can produce. But this is certain, that the known 

 terrestrial substances are widely diffused in space, and 

 especially nitrogen, which constitutes the greater part 



