1889." 



of the various Species of Heavenly Bodies. 



233 



The following table shows the above figures in another form and 

 includes the bright lines recorded in 7-Cassiopeiee : 



The chemical substances indicated by Duner's bands, and by the 

 lines in 7-Cassiopeiae, are those constituents of meteorites which are 

 volatilised at the lowest temperatures, namely, magnesium, man- 

 ganese, and lead. Besides these there are compounds of carbon, 

 which, when rendered incandescent, give the carbon flutings. 



In discussing the meteoric dust theory, as first enunciated by 

 Olmsted during the display of 1833, spectroscopists lost sight of the 

 importance of considering the volatility of meteoric constituents, 

 instead of quantities. Iron exists in great quantity in meteorites, 

 and was naturally the first thing to be expected in the aurora spectrum, 

 supposing it to be a meteoritic phenomenon. But, as I pointed out 

 in my paper to the Royal Society on November 17, 1887, experiments 

 on the luminous phenomena seen at low temperatures show that if 

 magnesium, manganese, and lead are present in meteorites, they will 

 be indicated in the spectrum before the iron. 



The experiments have shown that a very small percentage of 

 manganese is sufficient to render the first fluting (558) visible. It 

 is the first fluting seen when ordinary iron wire is volatilised in 



* This line is seen as a pretty bright line in the spectrum of the Limerick 

 meteorite, but its origin has not yet been determined, although comparisons have 

 been made with most of the common elements. So far, it has not been observed in 

 any other meteorite. 



