AND SCHONBEm 61 



should have a decidedly higher density. Indeed I do 

 not think the problem is yet in a position to be 

 solved. You must submit the older experiments of 

 Gottling l and Bockmann 2 to revision ; it is possible 

 that in their papers on the luminescence of phos- 

 phorus in nitrogen (particularly in that of the latter, 

 who declares that nitrogen disappears) you may find 

 facts which will suggest to you new methods of 

 research. The investigation is so important that you 

 must follow it up with the true Bunsen perseverance, 3 

 and not abandon it until, if possible, we are perfectly 

 clear about it. 



I wish you patience and good luck in your research ; 

 and with assurances of the greatest respect, 

 I remain, 



Yours most sincerely, 



JAC. BERZELIUS. 



1 Johann Friedrich August Gottling, born at Derenburg near 

 Halberstadt in 1755, died at Jena 1809. He was first an 

 apothecary, and then professor of chemistry, pharmacy, and 

 technology at Jena : " Etwas u'ber den Stickstoff und das 

 Leuchten das Phosphors in Stickluft," Cfren. Neues Journ., vol. 

 i. (1795) p. 1. 



2 Carl Wilhelm Bockmann, born at Karlsruhe in 1773, died 

 in 1821, teacher of physics at the gymnasium there : " Ver- 

 suche u'ber das Verhalten des Phosphors in verschiedenen 

 Gasen," Erlangen, 1800. 



3 He no doubt alludes in particular to Bunsen's investigations 

 on cacodyl which were begun in 1837, and whose conclusion 

 Berzelius had announced in the volume of the Jahresbericht 

 which was laid before the Academy on 31st March. 



