'Transmission of Emanations of Phosphorus through Air. 391 



(2nd) The Swan spectrum is that of an oxide of carbon as it 

 is only produced by carbon monoxide ; and as this 

 spectrum is changed at once into the carbon-oxide 

 spectrum by admission of oxygen or by intense electric 

 discharge, and, further, as the carbon-oxide spectrum 

 is invariably given by carbon dioxide, there can be no 

 doubt that 



(3rd) The Swan spectrum is that of carbon monoxide, and the 

 carbon oxide spectrum that of carbon dioxide. 

 We wish to express our indebtedness to Professor Ramsay 



for the great interest he has taken in the experiments. 

 Spectroscopic Laboratory, 

 University College, London, June 1901. /J) £ 



XL. The Transmission of the Emanations of Phosphorus 



through Air and other Media. — III. By C. Barus*. 

 1. rflHE experiments of the present paper are made with 

 JL an electrical method. They relate to the apparent 

 decay of the ionization produced by phosphorus, in the lapse 

 of time, for fixed distances apart of the condenser-plates ; to 

 the transmission of the ionization through layers of air and 

 other media and barriers. They are thus preliminary to the 

 subsequent experiments, in which the condenser and the 

 colour-tube are combined and the coincident effects inter- 

 preted. I hope, moreover, to decide whether a form of 

 radiation from phosphorus is presumable, or whether the case 

 is merely that of an ionized gas exhaled by the slowly 

 oxidizing body. I shall venture to treat the results in a 

 simple and direct manner, in order to present them more con- 

 sistently with my earlier papers f on the same subject, in 

 which the attempt was made to arrive at the ion velocity of 

 the phosphorus emanation by a non-electrical method, and 

 therefore in the absence of an electrical field. Finally, I 

 want in particular to ascertain whether, by giving less promi- 

 nence to the decay of ions by mutual destruction within the 

 element of volume, or otherwise, the phenomena may not be 

 reasonably explained. 



* Communicated bv the Author. 



t ' Science,' xi. p. 201 (1900) ; xiii. p. 501 (1901) ; Physical Review, x. 

 p. 257 (1900) ; and the current numbers of this Magazine. The ionization 

 of the phosphorus emanation was known to Matteuci, and has been studied 

 since by Neccari. It was rediscovered bv Bidwell (' Nature,' Dec, p. 212, 

 1893). Of. ' Nature,' lv. pp. (3, 125, 155 (1897) ; also xlix. p. 363 (1894). 

 1 believe to have been the first to point out its remarkable activity in 

 producing condensation, and the substance is specially interesting to me 

 because of this property. Cf. Bulletin N ). 12, U.S. Weather Bureau, 

 "Washington, 1895. 



2 D 2 



