the Occurrence of Enhanced Lines in the Arc. 851 

 Table I.— Magnesium. 



a. Quartz spectrograph. X 2150-A, 3200. 

 Observations were made on the spectra of the direct arc, 



water arc, and capacity spark. The water arc brings out a 

 series of hazy lines, all well visible and of which the least 

 refrangible one is even fairly strong. These lines had pre- 

 viously been observed only by Kayser and Bunge as very 

 feeble lines in the arc. They are absent from the spark. 



XA 2605-3 Fairly well visible. ^ 



26304 Well'visible. I m v * *. r ,u w 



26330 Very well visible. lhes ? 1 ™ B *"" P /. 1 I** 



26682 Bather feeble. ! nebulou s ser J es . of triplets ; 



2672-8 Well visible. > no member of the 2nd series 



9700.0 -p. 1 1 nas been observed m this part 



2733-7 Fairly "strong. of the spectrum. 



2736-7 Fairly strong. J 



X 2777 to X 2784 A group of lines identical in water arc and spark ; in 



direct ordinary arc, lines are widened and. X 2780 



is reversed. 



oo~2 > Keversed in direct arc and spark, but not in water arc. 



2852 Doubly reversed in direct arc ; simply reversed in water arc 



^>Q9« I Of equal appearance in the three spectra ; but the halos 

 oqo~ | are less marked in water arc. 



qrvQo \ Same in water arc and spark ; reversed in direct arc. 

 3096 Same in the three sources. 



b. Uviol spectrograph. A. 3170-X 5000. 



XX 3330 1 



3332 I Intense Hues ; same in the three sources. 



3337 J 



3722 Strong and very hazy in water arc ; ^ ■«• . „■ : „ + i , 



- . 9 n • j- i. j JSot given in any tables, 



fair v well seen in direct arc and m „ f -i ■ • 



,•' i 1 Two ot the lines are 



ounn n7 S M r * i i i- • > marked in the atlas of 



W2b Fairly strong and very hazy m b fl 



Qh01) water arc ; ? 1T feeble m Qlrect Valenta. 

 o/32 J arc and spark. J 



3829 Stroug and very hazy ; same in the three sources. 



3832 "I Intense and very hazy; same in water arc and spark; 



3838 J reversed in direct arc. 



3890] 



3892 I Fairly strong and hazy in the three sources. 



3896 J 



4058 1 Strong and sharp in water arc; hazy and feeble in direct arc 



4168 ] and spark. 



4352 Stronger in water arc than in direct arc or spark. 



4481 Very strong in water arc ; very feeble in direct arc ; intense 



and expanded in spark. 

 4571 Very strong in water arc ; only feebly brought out in direct 



arc and spark. 

 4703 Of identical appearance in the three sources. 



The green band at X5007 has come out only in the water 

 arc. 



3 I 2 



