880 
PEOFESSOE W. A. MILLEE ON THE PHOTOOEAPHIC 
36. Copper. — The spectrum of this metal is considerably prolonged. The intensity 
of the light from copper points is liable to vary considerably during the course of an 
experiment, being apparently much influenced by the slight changes of form experienced 
by the electrodes in consequence of the action of the discharge upon them. In these 
experiments I always used thin sheets of electrotype copper. The most marked lines in 
the spectrum of copper are the following: viz., two close together at lll’T and 112-3; 
these are followed by three strong nearly equidistant groups of dots at 128, 136-6, and 
146-7 ; a very strong group appears at 156-7 ; and the spectrum ends at about 181-5, with 
a series of much fainter groups. (Plate XXXIX. flg. 12, & Plate XL. flg. 40.) 
37. Tin. — The spectrum of this metal shows at 107-0 and 112-5 a pah- of strong double 
dots, at 114 another dotted line, at 118-0 a strong double line; characteristic groups 
of dots commence at about 122-0 and 129-5 ; between 130 and 134 it exhibits three 
strong groups, followed by several well-marked pairs of dots to about 154, after which 
it terminates rather abruptly by four nearly equidistant faint groups at about 163. 
(Fig. 13.) 
38. Bismuth. — This metal furnishes a strong and well-marked spectrum. Five pairs 
of dots show themselves between the line H and the nitrogen line 111*5 ; a strong pair 
is then seen at 115-3, followed by flve strong groups, each of which is triple ; the fli-st of 
these is the most intense ; these are followed by an intense group, which terminates at 
122-0 ; beyond these the spectrum is continued by a numerous and intense series of 
groups of dots, particularly at 143 and 157, and terminates at about 158. (Fig. 14.) 
39. Antimony. — The spectrum of antimony is also very characteristic. A triple series 
of groups of dotted lines commences at about 104-5 ; the nitrogen line at 110-5 is very 
intense ; at 113 is a strong double line followed by seven or eight intense groups of dots 
which terminate at about 138-5 ; at 150-5 is a group of moderate intensity ; and the last 
traces of lines disappear at about 164-0. (Pigs. 15 & 41.) 
40. Arsenic. — The characteristic dotted lines of this spectrum commence at 115-0; a 
series of groups occur very close together, ending at about 129-0 ; then follow six 
fainter irregular groups ; and the spectrum terminates abruptly with three very strong 
groups — the flrst two of which nearly run into each other, succeeded by an interval, the 
last group ending at 155. (Fig. 16.) 
41. Tellurium. — This spectrum is highly characteristic. It exhibits a close series of 
dots, commencing at about 106, and terminating by a very strong group at 147-5. There 
is then a complete blank, till at 156 another group is seen, then an interval, and the 
spectrum terminates abruptly with a well-defined group at 168-5. (Fig. 17.) 
42. Tungsten. — This spectrum is not very intense. It shows a double dotted line at 
114, and a stronger one at 125 ; it is prolonged by a distinct series of dots to about 
145, and fades out at about 168. (Fig. 19.) 
43. Molybdenum. — The spectrum of this metal resembles that of tungsten, but is 
more intense. It is prolonged by a very faint termination to about 157. (Fig. 20.) 
44. Chromium shows a group of dots at 106-0, then a strong line at 114-5, then 
