MORSE. — SPECTRA OF WEHNELT. 



535 



could be distinctly seen have been placed in the Wehnelt column of the 

 table of wave-lengths. 



ZINC. [Plate 3, Fio. 10.] 



Spark. Zinc electrodes. 



Arc. Metallic zinc on carbon electrodes. 



Wehnelt. Zinc wire in hydrochloric acid. 



Beside the above lines there are present in the spectrum of the 

 Wehnelt the lines of an underlying band spectrum with heads at ap- 

 proximately A 3848.0, A 4238.0, X 4257.0, X 4299.0, X 4325.0. The finer 

 detail of these bands, from photographs in the third spectrum, will be 

 given in a later paper. The heads of the flutings of the strongest and 

 longest band have wave-lengths as follows: 



The spectrum of a zinc point used as active electrode offers many 

 interesting differences from the spark and arc spectra of the metal. 



1. The triplets X 3282.5, X 3302.5, X 3345.5, and X 4680.0, X 4722.0, 

 A 4811.0, are present with about the same relative intensities as in spark 

 and arc. The lines A 3683.0, A 4059.0, A 4630.0, which are strong in 

 the arc and absent from the spark, are present in the Wehnelt spectrum 

 with lower intensities, but about the same ratio of intensity as in the 

 arc. The lines A 4911.0 and A 4924.0, strong spark lines which are absent 



