Pottok and Lronarp—On the Spectra of Cerium, §c. 265 
QUANTITATIVE SpEcTRUM oF CERIUM CHLORIDE—continued. 
ee > Wave- Intensity Mee Wave- Intensity 
men t, length. Ener, JLo: length. Bees: 
Bs inca, z59 Inch. 
299°5 4444-5 4" 422-0 3234-4 | 1 ¢ 
300-7 4428-1 3° 424-3 3219-1 lo 
301°3 4419-0 6 o 427-2 3201°9 lo 
301-9 4410°8 26 428°3 3195-0 1" ¢ 
303-0 4391°8 5 432-3 3169-4 lo 
303-8 4382°3 5 436°7 3144:1 2" 
304°8 4064°8 4 440-7 3122-9 Au No. 17 
305°6 4352°9 36 453-0 3056°7 O" x 
308-0 4315-4 Au No. 11 458-2 3029-3 Au No. 18 
309-5 4296-9 8 482°2 2913-6 Au No. 19 
310-0 4285-5 36 502-2 2825°6 Au No. 20 
311°3 4270°9 3" 516°6 2768°5 1¢@ 
317°5 4181°3 3x 521-7 2748°3 Au No. 21 
318-8 4165°7 10 x 541°4 2676°1 Au No. 22 
326-9 4065°2 Au No. 12 548°6 2651°1 1 
337°3 3940°5 3” x 549-1 2649°5 1 
341°3 3898:0 | Au No. 13 551-4 2641°6 Au No. 23 
358-0 3730°1 1” 554°5 2635°3 1¢ 
359-0 3720-0 1" o 562°9 2603-7 3x 
360-0 3709-5 3” 567-2 2590-2 Au No. 24 
373-5 3586°7 Au No. 14 571°6 2578°4 19 
399-6 3383-0 Au No. 15 580°5 2548°9 1» 
414-6 3280-8 Au No. 16 582-0 2544-3 Au No. 25 
420°3 3243°6 1” o 
LANTHANUM. 
Plate XXI., spectra 1 to 6, shows the gradual extinction of 
the lines of lanthanum on dilution; and Plates XXII. and 
XXITI., spectra 5 and 6, show the spectra of lanthanum chloride 
in solutions containing respectively 10 per cent. and 1 per cent. of 
the element. Lanthanum has a strong characteristic spectrum, of 
