98 C. Barus — Repulsion of Two Metallic Disks. 



10 3 ?/=100 90 85 80 75 70 68 67 66'8 66'68 1/15 cm. 

 t= -4 -7 1'2 1-9 3-7 5-5 8*5 10*5 19*4 oo sec. 



These values with the equation show that the position of 

 equilibrium is reached to AiV = 10~ 4 , the smallest quantity 

 easily measurable in about 25 seconds. 



The fluid has been treated as incompressible, seeing that the 

 pressure excess is a very small part of the total pressure. In 

 endeavoring to use the gas equations directly, I have not suc- 

 ceeded in producing a practical form of equation. 



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2.15 



6. Observations continued. Presence and absence of elec- 

 trical contact.— Notwithstanding the improbability of electri- 

 cal effects, it was thought necessary to test the case directly. 

 Accordingly in fig. 3, series 1-8, experiments are recorded 

 with the plates not in metallic contact (series 1-5), and with 

 the plates in metallic contact (series 6-8), respectively. The 

 behavior in both cases is virtually the same, when the inevita- 

 ble shift of zero is taken into account. Observations are 

 plotted in time series (minutes), and they are in each case con- 

 tinued until the motion of the plate is retrograde, whereupon 

 the slow oscillation of the plate begins. To throw further 

 light on the subject, a Leclanche cell was introduced in series 

 9 and 10 and removed in series 11. The lighting circuit of 

 the room was placed more remote in series 12 and the system 

 earthed in series 13 and 14, at both fixed discs. 



That the differences observed are referable to the incidental 

 shifting of the zero, is shown in series 1 5-18, where observa- 

 tions are made on one side only, with the distance between 



