KENT. — SPECTRA OF THE ZINC ARC AND SPARK. 101 



amp. were noted, but upon change of polarity and in the single order 

 condition, the fluting changed into three components, the one lying 

 toward the red being the faintest of the three; moreoever, at times 

 six components appeared, the four toward the red being well marked. 



At 8.8 amp. the changes were sudden and well defined. The con- 

 dition was nearly that of the single order, the higher order being 

 slightly stronger. The central component was lacking and the four 

 side components appeared far apart, the two innermost being the 

 strongest. Then at times the central line appeared, attended by two 

 hazy satellites, the left one of which was often the strongest of all three 

 lines. A sudden change here occurred to a very broad image, show- 

 ing no structure. New zinc was then supplied and there eventually 

 appeared two well-marked lines far apart; these gradually approached 

 each other, a line developed between them, and all three of these lines 

 were at times of the same intensity. Finally, with lessening vapor 

 density, the central component became stronger and the two outer 

 ones shrank toward it. 



Zinc 4722. Current 1.3 amp. single order condition. The same 

 general phenomena obtained following the first fluting, which was 

 poorly marked. There appeared two lines, the left a little stronger 

 than the right. These eventually reduced to a single line. 



At 2.5 amp. there appeared a single line between two faint satellites. 

 The right component of the three was stronger than the left at certain 

 times ; whereas, the arrangement of the orders was such that it would 

 be weaker. With low vapor density the system became a single line. 



At 3.5 amp. three lines of nearly equal intensity appeared, the 

 two on the outside somewhat fainter than the central one, which 

 last was the sharpest of all. The outside components often became 

 broader and finally there resulted one single, sharp line with a faint 

 suggestion of side lines at times of greatest brilliancy. 



At 5.5 amp. and nearly a double order condition, a central compo- 

 nent and two broad satellites were found. 



At 8.8 amp. and using carbon terminals, in the single order condi- 

 tion, at first the field showed no structure, then followed the fluting, 

 then there appeared three lines, the right and left strong, the central 

 onfe weak and diffuse. Finally the left component disappeared, the 

 central one became as intense as its fellow; then the two merged into 

 a single fine line. 



Zinc 4680. At 1.2 amp. and a nearly double order condition, 

 after the fluting there followed a condition marked by two components 

 nearly equal in intensity, followed by a single line. 



