Royal Society. 473 



This seems to indicate that a high temperature is necessary to bring 

 out the blue ray. Ever yours sincerely, 



E. Fkankland. 



P.S. I have just made some further experiments on the lithium 

 spectrum, and they conclusively prove that the appearance of the 

 blue line entirely depends upon temperature. The spectrum of 

 chloride of lithium ignited in a Bunsen's-burner flame does not dis- 

 close the faintest trace of the blue line : replace the Bunsen's burner 

 by a jet of hydrogen (the temperature of which is higher than that 

 of the Bunsen's burner), and the blue line appears, faint, it is true, 

 but sharp and quite unmistakeable ; if oxygen be now slowly turned 

 into the jet, the brilliancy of the blue line increases until the tempe- 

 rature of the flame rises high enough to fuse the platinum and thus 

 put an end to the experiment. — E. F. 

 . November 22, 1361. 



[On the occasion referred to by Dr. Frankland, it was a general 

 impression among the chemists present at the lecture that I had used 

 the word lithium for strontium throughout the evening. This induced 

 me to ask Dr. Miller to test my chloride of lithium, which he found 

 quite pure. I afterwards showed the blue band, the splendour of 

 which is unrivalled, to my class at the School of Mines. The coal- 

 points without the lithium show nothing of the land ; with the 

 lithium the band always appears. Either therefore the substance 

 itself is so altered by the exalted temperature that new periods of 

 oscillation are possible to it, or the medium in which it vibrates is so 

 changed in elasticity as to permit of the same tiling. The obser- 

 vation appears to be one of considerable significance. I would also 

 draw attention to the experiment by which the absorption of the 

 yellow band by the sodium flame was effected on the same occasion, 

 as one of the most striking class experiments in the whole range of 

 optics. It is very easily performed, a band 18 inches long and -f of 

 an inch wide being quite attainable within ordinary lecture-room 

 limits. A salt flame 10 feet thick produced no such effect. Dr. 

 Miller, I am informed, repeated this experiment with success before 

 an evening meeting of the British Association at Manchester (see 

 Phil. Mag. vol. xxii. p. 154).— J. T.] 



LXI. Proceedings of Learned Societies. 



ROYAL SOCIETY. 

 [Continued from p. 403.] 

 December 20, 1860. — Major-General Sabine, It. A., Treasurer and 

 Vice-President in the Chair. 



THE following communications were read : — 

 " Researches on the Arsenic-Bases." By A. W. Ilofmann, 

 LL.D., F.R.S. 



In a previous note* I have shown the existence of a group of dia- 



* Phil. Mag. for September, p. 245, " Researches on the Phosphorus-Bases. 

 No. IX. Phospharsonium Compounds." 



Phil. Mag. S. 4. Vol. 22. No. 149. Dec. 1861. 21 



