208 



REPORTS 01^ INVESTIGATIONS AND PROJECTS. 



(except at earthed points) and the greater faciUty of surrounding the insu- 

 lated conductors with dry, dust-free air. 



An extended series of experiments on sulphur has been completed, a series 

 on rosin has been nearly completed, and experiments on ebonite and paraffin 

 have been begun. In these experiments a bronze cylinder A rotates sym- 

 metrically v^ithin a large cylindrical coil of copper wire wound on a brass 

 bobbin. The bearings BB, in which A moves, are of lumen, and are screwed 

 to the flanges forming the ends of the brass bobbin. The dielectric under 

 investigation is in the form of a hollow cylinder F, cast on the rotor A, 

 coaxial with it, and of the same length as its central portion of uniform 



Earth 



R/ S 

 •JVA/WWWW 



6 SI 



Corrdenser 



BectiDineter 



q2 To D 



ToE 



Inlet for dry 

 dust free air 



diameter. The dielectric cylinder is covered 

 with a thin conducting coat. A little longer 

 than F, and surrounding it coaxially is a uni- 

 form brass tube E. Surrounding this are co- 

 axial brass tubes L and M, the latter forming 

 part of the bobbin, and both together, with the 

 brass rings soldered between them near the 

 ends, forming a water-jacket. The tube E is 

 insulated from L by small blocks of amberoid. Between E and Z, is a brass 

 rod DD, capable of being rotated in the metal bearings / and P near its ends. 

 The rod is cut near its right end and the two parts are separated by a block of 

 amberoid /. At the left end the bearing / is insulated by means of a sur- 

 rounding amberoid block K. Screwed to the insulated part of the rod Z) is a 

 brass wire H, by which D may be brought into electrical connection with the 

 metal coat of F without touching the cylinder E. For this purpose a small 

 opening Q is made in E. Small ebonite rings GG make the electrical contacts 

 between the rotor A and the bearings BB, which are earthed, always nearly 

 the same. Brass tubes CC, of very nearly the same diameter as that of the 



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