PLATE 3. 



Fig. 10. a. Spectrum of spark in air between zinc terminals. 



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



c. Spectrum of zinc point in hydrochloric acid. 



Fig. 11. a. Spectrum of spark in air between amalgamated copper terminals. 



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



c. Spectrum of platinum point in solution of mercuric nitrate. 



Fig. 12. a. Spectrum of spark in air between tin terminals. 



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



c. Spectrum of tin point in hydrochloric acid. 



