﻿8G8 Dr. E. N. da C. Andrade on the Carriers of 



luminous streak itself, it is found to be smaller than in the 

 pure flame, but, with such amounts of salt as were used, by 

 not more than 20 per cent. It is to be noticed that this is 

 the case when the potential is maintained by cold electrodes 

 outside the flame ; when the electrodes maintaining the 

 potential are platinum glowing in the flame, as in all previous 

 experiments on the velocity of the faster positive carriers, 

 the case is very different, the distribution of potential being 

 very much altered by the presence of the salt in contact with 

 one or both of the glowing electrodes. 



§ 3. Determination of the Velocity from the distribution 

 of the faster earners. 



When the insulated platinum strip is opposite the flame, 

 and the insulated electrode is positively charged, there is a 

 deflexion of the galvanometer, which remains constant as 

 long as the field remains on : this is due to positive carriers 

 present in the pure flame being driven out onto the strip. 

 On the introduction of the bead of salt into the flame a 

 further deflexion in the same direction is observed, showing 

 that there. are positive carriers which can be driven out of 

 the flame contained in the metal vapour. The amount of 

 this further deflexion gives a measure of the number of 

 metallic carriers arriving at the particular region occupied 

 by the strip. The extra current due to the introduction of 

 the metal salt into the flame will in future be referred to as 

 the " metallic current," and the corresponding deflexion of 

 the galvanometer as the "metallic deflexion. " 



The fields used were usually not strong enough to produce- 

 a marked deflexion of the coloured streak : this could always 

 be produced by increasing the field, but the smaller fields 

 were used as being steadier. Some measurements of the 

 velocity of the Lenard carriers deduced from the deflexion of 



a just visible streak of vapour gave 0*04 ^^ /12- £ or 



cm /volt sec '? CHI - 



strontium* : Lenard gives 0*08 — '- / for lithium, and 



secy cm. 



states that the velocity for strontium is smaller. 



The distribution of the faster carriers was investigated by 



measuring the number of carriers, as measured by the 



metallic current, to be observed with the platinum strip at 



* Since these measurements were made G. Ebert has published a 



paper (Heidelberg Dissertation, 1911) where he gives 0*042 — ' /I2_ 



& sec. / em. 



for Sr. 



