482 



PROFESSOR W. E. AYRTON, MR. T. MATHER AND MR. F. E. SMITH : 



pads of silk moistened with alcohol and afterwards between two pads of dry silk. 

 From time to time the strands were examined with a lens, but nothing unsatisfactory 

 was observed. When the winding was complete except for about 10 centims. of the 

 last turn, the lathe was stopped, and a long U-shaped clamp slipped over that end of 

 the cylinder farthest from the face plate ; a grooved piece of ebonite was placed over 

 the last strand and the latter clamped between the ebonite and the marble ; this 



Fig. 9. Method of supporting the suspended cylinders during turning. 



enabled the tension on the wire of the bobbin to be relaxed. A length of wire 

 sufficient to complete the connections was then measured off, the free end passed 

 through the radial hole d, fig. 8, along the V-groove/y, through a, and finally secured 

 to the nipple by soldering. Throughout these operations the wire was kept as taut 

 as possible. On the completion of the helix the clamp was 

 !{ removed, the V-grooves filled in with paraffin wax, and the 



cylinder wrapped round with silk. It was then removed for 

 diametral and axial measurements. 



The turning f two small cylinders for the suspended coils was 

 completed in a manner very similar to that described for the 

 large cylinders, but as the ellipticity of these was comparatively 

 great, they were rejected. Two other cylinders were chosen and 

 their inner and end surfaces turned as in the previous cases, but 

 their outer surfaces were turned between dead centres. The 

 arrangement is shown in fig. 9. A, B, and C are tight-fitting 

 collars on the mandril M ; the outer collars have shoulders, and 

 these and the collar B are turned so as to be a good fit in the 

 cylinders, which are clamped between A and C by means of three 

 bolts. The outer surfaces of the cylinders were finished in this 

 way, and afterwards the double spiral grooves were cut; the 

 result is very satisfactory. 



The connections to the suspended coils (fig. 10) are much 



Fig. 10. Part section of 

 suspended cylinder 

 showing leads to coil. 



simpler than those for the fixed coils. The terminating nipples are placed inside 

 the cylinder and one-half of each is cut away where it projects from the marble ; the 



