42 



Dr. E. H. Cook on Experiments 



The angle of the point makes a considerable difference to 

 the shape of the positive fan. If the end consists of a small 

 angle, for example a needle, the bounding lines of the fan 

 enclose a small angle, and the whole of the luminous portion 



45 000 



VOLTS 



86.000 



VOLTS 



26 000 



VOLTS 



45/000 



VOLTS 



50.000 



VOLTS 



is very small. As the angle increases so does also the angle 

 of the fan. The figures show the kinds of discharge obtained 

 from brass points of varying angles. They were obtained 

 from the positive side of a machine, and under similar con- 

 ditions of proximity to earth-connected plates. The dis- 

 charges are drawn of about actual size, but the wires and 

 points are drawn larger than they were for the sake of 

 clearness. The approximate differences of potential between 

 the knobs of the machine when giving these discharges are 



