396 THE CHEMISTRY OF THE SUN. [CHAP. 



On the addition of aluminium, the lines 4962, 4895 (4893, Huggins) 

 and 4868 (4867, Thalen), were also reversed. 1 



Note. The naked arc photographed at Kensington in 1875, shows 

 the reversal of 4607'6, 4303-3, and 4215-3. 



The line 4895 is not noticed by Thalen at all, but Huggins gives 

 a line at 4893. It is a question therefore, if this line is not due to 

 impurity, whether 4895 may not be a new line due to a combination 

 of the finer molecules of aluminium and strontium, just as the new 

 lines of magnesium and sodium, magnesium and potassium, and 

 magnesium and hydrogen, as mapped by Messrs. Liveing and 

 Dewar, most probably are. 



Lead, introduced as metal into the Siemens' arc in a lime crucible, 

 reverses the line 4058, but lead ferro-cyanide treated in the same 

 way, reverses 4058 and 4032. 2 



Chromium as oxide or bichromate of ammonia in Siemens' arc 

 in the lime crucible gives no reversals. On the introduction of 

 hydrogen, the following lines are easily reversed, viz. : 



The green triplet .... 5207, 5205, 5203. 



The indigo triplet .... 4289, 4274, 4253. 



The triplet near N . . . . 3578, 3593, 3606. 



The double below about . 3446. 



And the triplet .... 2799'8, 2797, 2794. 3 



Magnesium alone in an arc of 30 cells in a lime crucible does not 

 reverse the b lines, but on the addition of aluminium the three 

 b lines are reversed in the inverse order of their refrangibility. 

 Magnesia alone does not give the reversal of the b lines with an arc 

 of 25 cells, but on adding aluminium the least refrangible member 

 appears reversed. 4 



Manganese sulphate alone in Siemens' arc in a lime crucible, shows 

 the reversal of the violet triplet 4029, 4032, 4033. On the addition 

 of magnesium, the bright blue lines 4823, 4783, and 4753, are 

 reversed, the least refrangible one being most easily reversed. 5 



Note. The Kensington photographs of the naked arc show the 

 reversal of the violet triplet, and the line 4080 which is not recorded 

 by Messrs. Liveing and Dewar. 



1 Proc. Roy. Soc. vol. xxviii. p. 473. 4 Ibid. vol. xxviii. p. 368. 



2 Ibid. vol. xxix. p. 404. 6 Ibid. vol. xxix. p. 404. 



3 Ibid. vol. xxxii. p. 405. 



