Kent. 



Spectra of the Zinc Arc and Spark. 



Plate 1, 



The following negatives, on Plates 1 

 and 2, represent approximately a three- 

 fold enlargement of the image as pho- 

 togi-aphed or a twelve-fold enlargement 

 of the echelon image. 



The region of longer wave-lengths 

 lies to the light. 



12 and IG were taken with the Porter 

 echelon; 28 to 96e with the Petitdidier 

 instrument. 



Much of the detail existing upon the 

 enlarged negatives is not appai'ent in 

 the reproductions herewith shown. 



12 



16 



u 



y 



28 



32 



1 1 



30 



I 

 f 



I 



52 



70a 



I 



I 



t 



Slh 



81d 



71a 



71c 



111b 



Proc. Amer. Acad. Arts and Sciences. Vol. XLVIII. 



