POPULAR SCIENCE. 11 



If the luminous portion of a prism-decomposed solar beam be- 

 looked at, certain black bands will be seen to traverse it, some 

 broader than others, but each one of invariable relative dimen- 

 sions and in one invariable place. Having been first pointed 

 out by Frauenhofer, they were known, and are still known, 

 by the name of Frauenhofer's lines. They remained a mys- 

 tery until Bunsen and Kirschoff solved it ; and out of their 

 solution came the modern spectrum analysis, which depends 

 upon the following essential facts. 



Every metal can be burned, and heat sufficient being em- 

 ployed, the burning mass can be made to evolve a vapour. 

 Every metal burns with a certain invariable colour, and the 

 light of these colours can be projected through a prism. If 

 so projected, a line across the spectral image results, of cer- 

 tain specific size and also colour ; but if the light of a burn- 

 ing mass of metal be transmitted through its own vapours, 

 then the band of colour it would have yielded on the spec- 

 trum is quenched as to colour, and the result is not colour, 

 but black. An indication of the nature and meaning of spec- 

 tral analysis was only aimed at in this place and at this time y 

 and the outlines given will be sufficient to the end. 



Whatever cavil the typical man of practice might raise 

 against the utility of spectrum analysis, he will not object to 

 the case now to follow. It is surely of some use to abolish a 

 manufacture that produces horrible disease, mostly fatal, and 

 at the same time to diminish the chances of fire. Amorphous 

 or allotropic phosphorus has accomplished this, or rather 

 might accomplish this. What, then, is allotropic or amor- 

 phous phosphorus ? Amorphous means devoid of form; in the 

 present example, crystalline form is alone referred to. Or- 

 dinary phosphorus crystallises, the amorphous variety does 

 not ; hence the name ' amorphous.' As for the word ' allo- 

 tropic,' it is a very puzzling word to have any discourse about. 

 Philosophers, of whatever kind, have long been used to em- 

 ploy certain words to comprehend certain phenomena which 



