396 



Or. \V. L. Robb on Oscillation.* 



1. Effect of Diminishing the Time. 



A series of determinations was made to find the effect ot 

 diminishing the time of contact of the spheres (see fig. 1) 

 upon the variations observed in the charge of the condenser. 

 The simplest way of varying with certainty the time of con- 

 tact was to use, as the smaller sphere, spheres of different 

 sizes. An increase in the diameter of the sphere lengthens 

 the time of contact. Three different spheres were used, and 

 in Tables II. and III. the results of twenty consecutive obser- 

 vations with each sphere are given. In the actual work, 

 however, at least fifty observations were always taken to ensure 

 that the observations given in the following tables were 

 representative in their character and included the extreme 

 variations. 



Table II. (See also diagram 2.) 

 Mica Condenser (normal charge* = 2*010 microcouloinbsj. 





Diameter of Sphere, 



Diameter of Sphere, 



1 Diameter of Sphere, 





S 2 =0-49 centiin. 



S 2 =0-79 centim. 



S 2 =2'16 centim. 



Observation 









1 





number. 



Cbarge of 



Deviation 



Charge of 



Deviation 



Charge of 



Deviation 





Condenser. 



from the 



Condenser. 



from the 



Condenser. 



from the 





Micro- 



normal 



Micro- 



normal 



Micro- 



normal 





coulombs. 



charge. 

 4-0-064 



j coulombs. 



charge. 



coulombs. 



charge. 



1 



2-074 



1-987 



-0-023 



1 983 



-0-027 



2 



2072 



+0-062 



2011 



+0001 



1-982 



-0028 



3 



1-971 



-0039 



1-988 



-0-022 



1-988 



-0022 



4 



2-120 



+0110 



1-994 



-0-016 



1-985 



-0-025 



5 



2136 



+0-126 



1-967 



-0043 



1-991 



-0019 



6 



2115 



+0105 



2-011 



+0-001 



1-983 



-0-027 



7 



2-071 



+0061 



1-996 



-0014 



1-9S0 



-0-030 



8 



2044 



+0034 



1-987 



-0023 



1-983 



-0027 



9 



2 061 



+0051 



2-021 



+0011 



1-982 



-0-028 



10 



2-038 



+0028 



1-985 



-0-025 



1-980 



-0030 



11 



2-065 



+0-055 



1986 



-0 024 



1-982 



-0028 



12 



2- J 50 



+ 0-140 



1-987 



-0 023 



1-988 



-0-022 



13 



2093 



+0-083 



1-976 



-0034 



1-985 



-0025 



14 



2 030 



+0 020 



2024 



+0014 



1-981 



- 0029 



15 



1-987 



-0 023 



1-971 



-0039 



1-988 



-0022 



16 



1-966 



-0 044 



1-969 



-0041 



1-983 



-0027 



17 



2-081 



+0 071 



1-984 



-0026 



1985 



-0025 



18 



2107 



+0097 



2-007 



-0003 



1983 



-0 027 



19 



2-060 



+0-050 



2009 



-0001 



1-980 



-0 030 



20 



2065 



+0-055 



2016 



+0-006 



1-988 



-0-022 



* By the term u normal charge " is meant the constant charge which 

 the condenser eventually assumes when charged for a considerable time. 



