Potxiox & Leonarp—On the Spectra of Barium, §c. 283 
tion to the residuary lines of these elements, which are all situated 
in the ultra-violet part of the spectrum above gold line No. 18, the © 
metal showed one or two very well-defined and intense lines that 
are either not shown at all by strong solutions, or only faintly 
shown: those lines are marked 7 in the table. ‘The dilution- 
spectrum of calcium was investigated by Sir William and Lady 
Huggins in a manner differing somewhat in detail from that 
adopted in the present experiments; but the conclusions are the 
same as regards the identity of the residuary lines. 
Plate XVIII.—Spectra 1, 2, and 3 show the spectra of the 
metal, a 10 per cent. solution, and a | per cent. solution. 
Quantitative Spectrum of Calcium Chloride. 
aE caste Wa a we Measure Mane Bee 
testy Shi : Persistency. aa eh. ’ Persistency. 
250-85 5594-6 8 « | 313:80 4289-5 Sis nich 
262°70 5270-5 Be 314-30 4283-2 8 
279-60 4878°3 6 «o || 318-25 4296-9 Oates 
283-80 [No. 9, | Gold.] 330°70 [No. 12, | Gold.] 
295-00 4586°1 4 6 338-85 3968-6 80 w 
295-50 4581-7 4 a || 341-90 3933°8 100 
a9s-50 | 4527-2 | [4] o || 346-10 [No. 13, | Gold.] 
302-85 4455-0 10 @ || 360-85 3737°2 boy 
304-05 4435-1 10 ¢ | 364-05 3706-2 10 ¥ 
304-75 4495-6 10 » || 371-00 3644°5 2 @ 
311-80 4318-8 8 | 872-60 3630°8 1g 
312-00 [No. 11, | Gold.] | 377-50 [No. 14, | Silver.] 
312-55 | 4307-9 6 o« || 43480 3179°4 10m ec 
313-00 4302°7 10 co || 488-35 3159°1 10 x 
313-20 4299-1 6 « || 444-70 [No. 17, | Gold.] 
MaGnEsIUM. 
Magnesium chloride was the salt used. Unlike barium, 
strontium, and calcium, the most persistent lines are situated in 
