546 Prof. Richardson and Mr. Hulbirt on the 



In view of the unexpected identity of the specific charge 

 of the positive ions from these three very different elements, 

 it seemed desirable that a greater variety of elements should 

 he examined. The present investigation was undertaken 

 with that object in view, and the materials which have been 

 experimented upon include platinum, palladium, gold, silver, 

 copper, nickel, iron, osmium, tantalum, tungsten, brass, 

 nichrome, and steel. In addition, unsuccessful experiments 

 were made upon aluminium, magnesium, and zinc. It was 

 found that the strips of these metals which were used in- 

 variably melted before sufficient ionization could be obtained 

 to carry out the necessary measurements. 



The foil from which the strips were cut varied in thickness 

 from *002 to *005 cm., depending on the material. Each 

 strip was cut as narrow as possible, none being more than 

 •02 cm. wide. 



The platinum, palladium, gold, and silver were cut from pure 

 foil supplied by Messrs. Johnson, Matthey & Co. The copper 

 was rolled from ordinary magnet wire, and the tantalum was 

 rolled from a filament out of a tantalum lamp. The source 

 of the other materials, where it is of interest or importance, 

 is stated in the context. 



Both the apparatus and the method of using it are precisely 

 the same as before. No change was made, even in detail, so 

 that for the description of the method it will be sufficient to 

 refer to the previous paper. We shall, therefore, content 

 ourselves with stating the results which have been obtained. 



Platinum. 



A number of new measurements of ejm have been made 

 for the positive ions from platinum, partly to compare with 

 the results obtained previously, and partly in order to test 

 the working of the apparatus from time to time. Different 

 values have been used both of the magnetic intensity and 

 the electrostatic potential difference. The results of the 

 measurements are given in the following table (p. 547). 



The quantity m/H represents the value of the ratio of the 

 mass of the positive ions to that of an atom of hydrogen on 

 the assumption that the charge on these ions is the same as 

 that carried by an atom of hydrogen in electrolysis. The 

 value of e\m for the hydrogen atom has been taken to be 

 9*66 X 10 3 e.m. units. 



It was pointed out in the previous paper that the absolute 

 values of ejm obtained by this method were subject to a 

 possible uncertainty arising from the theoretical conditions not 



