260 



some other part of the building. It required at least two hours to complete 

 the four series. The current and potential were read just before the pho- 

 tographic plate was exposed. 



ELECTROSTATIC AND MAGNETIC FIELDS. 



The magnet was again placed in the position so that the line of dis- 

 charge between the points was transverse to the magnetic lines of force, 

 and with the electrostatic plates above and below the points, an attempt 

 was made to balance the effect of the electrostatic field against that of the 

 magnetic field. In this work the plates were charged by a Holtz machine 

 with plates 43 cm. in diameter. A ground glass placed in the end of the 

 camera opposite the pinhole showed clearly the path of discharge. The 

 speed of the Holtz machine and the strength of the exciting current of 

 the magnet were then regulated until the stream under the action of both 

 fields was the same as when no field influenced it ; then, the ground glass 

 was removed and was replaced by a photographic plate. Two series of 

 these photographs are shown here, M. for the spark discharge which, under 

 the influence of magnetism alone was changed to brush, and N for the rich 

 spark. It was not difficult to balance the two fields in the case of the 

 rich spark, but with the unstable spark they were not successfully balanced. 

 Sometimes with this type a very low magnetic field seemed to predominate 

 over the electric field. This, if true, conforms with the statement made 

 in the previous report that the ]}iagnetic effect is greatest when the dis- 

 charge is on the verge of changing from one form to the other. Data as 

 follows : 



Distance between points, 18.05 cm. II is the magnetic field strength in 

 gausses. 



Table 4. 





Distance 



















between 

 Plates 

 in cm. 



Potential 

 DiSerence 

 in Volts 



Potential 



Gradient 



= X 



H 



Velocity of 

 Ion 



Form of 

 Discharge 



Values for 



e 







m 





1 



5.4 



14600 



2710 



4300 



6.3x10^ 



small brush 



7.8 xlO'^ 





2 



5.4 



14600 



2710 



4300 



6.3x10" 



occasional spark 



7.5 xl02 





3 



54 



15000 



2780 



2550 



1.9x10^ 



" 



7.1 xlO^ 





4 



5.4 



15000 



2780 



3800 



7.4x10^ 



rich spark 



1.2 xlO^ 









6.1 



26800 



4360 



1600 



2.7x10^ 



spark 



1.36 xlO^ 



Series M 



6 



0.1 



26800 



4360 



1600 



2.7x10* 



rich spark 



1.36x10'' 



Series N 



