168 



MR. CHAUI.MS DM WATTKVILLK ON FLA MM Sl'ECTKA. 



IRON continued. 



DESCRIPTION OF PLATK 4. 



1. Flame spectrum of potassium (see p. 161). 



2, 3, 4. Spectra of iron, nickel, and colwilt. In the centre of each of them the oscillatory spark spectrum 



divides the name spectrum in two regions of which the one corresponds to the inner cone, while 

 the other corresponds to the upper portion of the flame. 



