1880.] on Investigations at High Temperatures. 261 



the tin, which allowed a capillary fihn of water to cover part of the 

 surface aud diftusc iuto the interior. 



When the ordinary Siemens' carbons were used as poles in this 

 almost dry atmosphere, tlie yield of hydrocyanic acid was still very 

 marked, purified carbons yielding the same results. 



As the yield of cyanogen compounds did not appear to be dimi- 

 nished, and it seemed almost impossible to get the largo volume of 

 air in the tin vessel perfectly dry, another plan was adopted. The 

 poles were enclosed in an egg-shaped glass globe about 8 inches long 

 and 6 inches in diameter, in order to diminish the volume of air to be 

 dried and dispense with the water covering. The globe, balanced 

 through a system of pulleys, was firmly attached to the lower or nega- 

 tive pole, with which it moved without impeding the automatic action 

 of the lamp. 



Dry air was sometimes forced through the negative carbon itself, 

 at other times through a glass tube passing up the side of it into the 

 globe, the products from the arc being drawn through the positive 

 pole as before. 



As the glass globe soon became very hot, and as a far larger 

 supply of dry air was forced through the globe than was drawn out 

 from the arc, it is inconceivable that any moisture could remain near 

 the arc after it had been in operation for a few minutes. 



Seven consecutive experiments, each of ten minutes' duration, 

 made with the same purified carbon poles, did not show any diminu- 

 tion in the quantity of hydrocyanic acid, unless in one of the experi- 

 ments, when the arc would not be drawn into the interior of the carbon 

 tube, but persisted in rotating round it.* 



These experiments show that drilled carbons even after prolonged 

 treatment with chlorine, still contained a quantity of combined 

 hydrogen, and organic analyses showed that the amount of ash and 

 combined hydrogen in the various samples was never less than about 

 • 75 of the former, and as much as * 1 of the latter. Poles made 

 with especially purified carbon by Messrs. Siemens for these experi- 

 ments proved to be no better in respect to the quantity of hydrogen 

 and ash they contained. 



The well-nigh impossible problem of eliminating hydrogen from 

 masses of carbon such as can be employed in experiments of this kind, 

 proves conclusively that the inference drawn by Mr. Lockyer,| as to 

 the elementary character of the so-called carbon spectrum from an 

 examination of the arc in dry chlorine, cannot be regarded as satis- 

 factory, seeing that undoubtedly hydrogen was present in the carbon, 

 and in all probability nitrogen in the chlorine. 



* Cyanogen is difficult to recognize in presence of prussic acid when in small 

 quantity, especially when impurities from the carbons complicate tlie tests. 

 In speaking generally of the formation of this acid in the arc, I do not mean 

 to exclude the possibility of cyanogen being formed as well. 



t " Note on the Existence of Carbon in the Coronal Atmosphere of the Sun," 

 Proc. Roy. Sec.,' vol. xxvii. p. 308. 



