and some of its Compounds. 311 



palladium wire increases often as much as fifty per cent, by 

 the occlusion of hydrogen. 



The increased length of the electric spark in an atmosphere 

 of hydrogen is not clue to an increased conductibility, but to a 

 dissociation of water vapor which is analogous to that which 

 takes place in a voltaic cell. 



These are some of the facts which lead me to believe that 

 hydrogen is an insulator and that the water vapor, therefore, 

 plays a controlling part in the passage of electricity through 

 gases. 1 am conscious that the conclusions in this paper are 

 somewhat radical ; and I have, therefore, worked assiduously, 

 during the past three years, to test them in every way which 

 my mind suggested, for it is not probable that many investi- 

 gators have at present twenty thousand storage cells, which 

 would enable them to repeat my experiments. The strength 

 of currents and the voltage I have employed have certainly 

 reached the limits of glass tubes to withstand such powerful 

 discharges. The form of tube figured in my previous article* 

 is the only one which I have found capable of withstanding 

 steady currents of one-tenth to one-fifth of an ampere, and 

 instantaneous condenser discharges of many hundred amperes. 



The great advantage of the use of a storage battery over the 

 employment of a Ruhmkorf coil; in the study of the ionization 

 and molinization of gases, is now T generally recognized. This 

 advantage is forcibly seen in the first experiment which I shall 

 bring forward in support of my view of the importance of the 

 role played by water vapor in the passage of electricity through 

 gases. A wide tube of the type I have referred to, the narrow 

 portion being approximately one centimeter, was provided 

 with massive copper-ring electrodes, oue inch in outside diam- 

 eter and one-eighth of an inch thick, which were heavily 

 electroplated with copper in order to avoid the impuri- 

 ties of commercial copper. The glass tubes were then 

 exhausted and filled with hydrogen made by the electrolysis of 

 distilled water and phosphoric pentoxide. The gas was sent 

 through tubes filled with caustic potash and many drying 

 tubes filled with phosphoric pentoxide. The gas was kept in 

 the drying tubes many hours ; and its flow was delayed by 

 partitions of glass wool. More than a litre of the gas was 

 used in the process of flushing out the spectrum tubes ; so that 

 the entire pump and connecting tubes were for several hours 

 presumably filled with hydrogen gas. 



When the tubes, having been exhausted to the most lumi- 

 nous stage, were excited by a condenser discharge and were 

 examined by a straight- vision spectroscope, the ordinary four- 



*This Journal, x, 222, 1900. 



