DEPARTMENT OF TERRESTRIAL MAGNETISM. 



335 



Table 8 shows the nature of the variations of the fields over the surface of 

 the sphere for the case of an observer moving with the surface of the sphere 

 and for the case of a stationary observer. The fields are expressed according 

 as their direction is like or unlike that of the Earth's field. 



The only influence which gives rise to an external electrostatic field is the 

 centrifugal-force effect. The field is, of course, very small ; it is a maximum 

 at the poles, where it acts vertically upwards and amounts to 4.5X10~^ 

 volt/cm. for the small sphere, and 2X10~^^ volt/cm. for the large sphere. 

 Except at the equator and poles the horizontal component of the field attains 

 a finite value. The internal electrostatic fields are, of course, such as to just 

 lialance the mechanical forces. For the centrifugal-force effect, the field is 

 perpendicular to the axis of rotation. On the surface, at the equator, it 

 amounts to 4.5 X lO"^ volt/cm. for the small sphere, and 2 X10~^^ volt/cm. 

 for the large sphere. For the gravitational and Thomson effects, the internal 

 field is radial. For the gravitational effect, it amounts, on the surface, to 

 2.8X10"^" volt/cm. for the small sphere and 5.5X10"^' volt/cm. for the 

 large sphere. For the Thomson effect it is, at each point, proportional to 

 the temperature gradient, and amounts to 2 X 10~~^ volt/cm. per gradient of 1° C. 



In the latter portion of the paper the solutions of the problems are extended 

 to fit the case of a sphere having a specific inductive capacity other than unity. 



