230 JONES-STRONG— THE ABSORPTION SPECTRA [April 24, 



ing and becoming more intense. At 6° the ultra-violet absorption 

 extended to A 3600. At 82° it had advanced to A 3800. Very nar- 

 row and fine bands appear at A 4186, A 4300, A 4308, 4345, 6240, 

 6265, 6290, 6305, and much broader bands at A 6380 and A 6740. 

 Wide bands occur at from AA4390 to 4480, AA4550 to 4850, AA4990 

 to 5340, AA5650 to 5950 and AA6760 to 6930, at 6°. At 82° these 

 bands have the following limits respectively : AA4380 to 4500, AA 4540 

 to 4910, AA4960 to 5370, AA5620 to 5990 and AA6730 to 6960. 



(/) Erbium Chloride. 



A spectrogram (B, Plate XIV.) was made to show the effect of 

 rise in temperature upon the absorption spectrum of a solution of 

 erbium chloride. For this purpose a 0.94 normal solution of erbium 

 was used and the depth of layer was 48 mm. The solution probably 

 contained a considerable number of impurities, so that in fact the 

 amount of erbium was quite small. The absorption spectrum was 

 found to change but little with rise in temperature, thus indicating 

 a dilute solution. Exposures were made for 30 sec. to the Nernst 

 glower and 4 mins. to the spark. The current through the glower 

 was 0.8 amperes and the slit width 0.20 mm. Starting with the 

 spectrum nearest the comparison scale the temperatures were 7°, 

 17°, 29°, 46°, 60°, 70° and 80°. 



At 70° the ultra-violet is absorbed to A 3950. As the temperature 

 is raised the ultra-violet absorption increases, and at 80° it reaches 

 A 3150. Bands from 20 to 40 Angstrom units wide occur at A 3235, 

 A 3510, A 3640 and A 3785. These bands are slightly wider at 80°, 

 but as for all the other erbium bands this widening is very small. 

 Weak and narrow bands appear at AA4165, 4425, 4458, 4500 

 (strong), 4535, 4540, 4555, 4580, 4685, 4750 (30 A. u. wide), 4810, 

 4840, 4855, 4870 (strong and 20 A. u. wide), and 4920, A 4920 lies 

 alongside of a fuzzy band extending from A 4910 to A 4950. 



After these comes a rather wide band which for a shorter length 

 of layer would most likely be broken up into a number of much 

 finer bands. This band extends from A 5190 to A 5250. At A 5217 

 there runs a narrow sharp line through the fuzzier and wider band. 

 Broad (about 30 A. u. wide) and very faint bands are located at 

 A 5630 and A 5760. For greater concentrations these would prob- 



