338 ADENEY 
Photographs of Spark Spectra from the Rowland Spectrometer. 
In conclusion, the author begs to express his sincere thanks to Professor W. N, 
Hartley, r.r.s., for much advice and assistance kindly afforded by him in the 
preparation of this communication. ‘The author is also indebted to Professor 
Hartley for the electrodes of iron, nickel, and cobalt employed in this research, 
and also for allowing him free access to his private collections of spectra and 
instruments. 
