Experiments and Inductions. 89 



an approximate Table of density of charge and angle of diver- 

 gence : — 



20°. 



30°. 



40°. 



55°. 



70°. 



87°. 



100°. 



Gold-leaf di liarges. 



o-io 



012 



0-14 



0-lti 



0-21 



0-27 



0-40 



1-00 



Limit of discharging effect of some pointed bodies. 



14. On centre of excited sulphur cake placed insulated B. D. 

 with small piece of gold-leaf stuck upon it : touched B. D., then 

 removed it by handle, and while it passed edge of cake a small 

 disk of sealing-wax was held opposite the gold-leaf to receive its 

 discharge (fig. 9). After repeating this three times, the disk 

 was laid upon cap of electroscope, and the leaves diverged 30°. 



] 5. The insulated B. D. with small piece of gold-leaf stuck on 

 rim, was placed on centre of strongly excited sulphur plate ; then 

 touched it with a wire and removed it from plate. The charge 

 thus obtained was subdivided to -\, and then applied to cap of 

 electroscope. The same operation was repeated without the 

 gold-leaf. In the first case the angle was 58°, in the second it 

 was 95°, thus showing that the gold-leaf appendage disabled 

 the B. D. from retaining electricity beyond a certain tension. 

 There was discharge from the gold-leaf in the act of leaving the 

 excited plate (14), as was made apparent by placing a small disk 

 of wax close to it at that instant, which, acting as a target for 

 the gold molecules then emitted, showed, when applied to the 

 electroscope, a strong charge of the same electricity as B. D. 



16. The same experiment was repeated with silver-leaf, which 

 gave angle 62°; platinum-foil, 50° ; tinfoil, 56°; lead-foil, 57° ; 

 iron wire yjoth of an inch in diameter, 62°. In each the charge 

 was reduced to -£th ; so they compare with each other and with 

 gold-leaf 58°. 



17. The same experiment was repeated with floss-silk fibre; 

 the charge was less than one-half that carried when gold-leaf 

 was attached, and it charged the wax disk on withdrawal of B. D. 

 same as the metal leaves. 



18. The same floss silk, when highly dried on sand-bath, 

 makes no discharge ; the angle was 93° with the fibre attached, 

 and the same without it. 



19. An extremely fine fibre of shell lac also makes no discharge 

 when one-eighth of the charge amounts to 93°. 



20. The following are similar observations taken in rainy 

 w r eather. The angle was of first contact. The charge retained 

 after the B.D. with appendage was removed from excited plate 

 was reduced to one-fourth. 



