PLATE 2. 



Fig. 7. a. Spectrum of arc in air. Lithium chloride on carbon terminals. 



b. Spectrum of spark in air. Lithium chloride on carbon terminals. 



c. Spectrum of carbon point in solution of lithium chloride. 



Fig. 8. a. Spectrum of spark in air between magnesium terminals. 



b. Spectrum of arc in air. Metallic magnesium on carbon terminals. 



c. Spectrum of magnesium point in hydrochloric acid. 



Fig. 9. a. Spectrum of spark in air between aluminium terminals. 



b. Spectrum of arc in air. Metallic aluminium on carbon terminals. 



c. Spectrum of aluminium point in hydrochloric acid. 



