Contents xv 



(2) EXPERIMENTS ON THE COMPARISON OF CHARGES 

 From MS. No. 9 (apparently prepared for publication) 



ARTICLES 



Intention of the experiments ........... 236 



Definition of the ratio of the charges of two bodies, illustrated by the comparison of 



a disk with a sphere ............ 237 



Method of the experiment ........... 238 



The [adjustable] trial plate. (Fig. 13) 239 



Arrangement of the apparatus 240 



Method of operation. (Fig. 14) 241 



Theory of the experiment 242 



Interpretation of the result ........... 243 



The testing electrometer ............ 244 



Method of testing ............. 245 



Advantages of the method 246 



Capacity of the trial plate 247 



The gauge electrometer ............ 248 



Form of electrometer used in the later experiments. (Fig. 30) 249 



Estimation of error arising from unequal electrification in the two trials . . . 250 

 Comparison of the capacities of two bodies . . . . . . . .251 



Demonstration 252 



Why the electrification is tested by the gauge electrometer 253 



The bodies to be tested were chosen of nearly equal capacity 254 



Measurements of the apparatus 255 



The insulating supports of waxed glass. (Fig. 16) ....... 255 



Electrification of air ............. 256 



Effects of the electrification of the air 257 



The earth-connexions 258 



The electrometer threads salted .......... 259 



Leakage of the Leyden vials 260 



Estimate of the accuracy of the experiments 261 



Probable cause of error ............ 262 



Weak charges always used 263 



Reason for this .............. 264 



Third experiment. On the effect of variations in the arrangement of the apparatus in 



testing capacities. (Fig. 17) ........... 265 



Six different arrangements ........... 266 



Result of the six arrangements ........... 267 



Conclusion .............. 268 



Fourth experiment. Capacities of bodies of different substances, but of the same shape 



and size .............. 269 



Glass coated with various substances ......... 270 



Method of the experiment 271 



Effect of the thickness of a plate on its capacity ....... 272 



Fifth experiment. Charge of two small circles compared with that of a large one. 



(Fig. 18) 273 



Results of the experiment 274 



The experiment repeated in a different manner . . . ^ 275 



Comparison with theory 276 



Remarks on the calculation 277 



Bearing on the theory ............ 278 



Sixth experiment. Charge of two short wires compared with that of one long one . 279 



Comparison with theory 280 



Seventh experiment. Comparison of the capacities of several bodies .... 281 



Comparison of disk with sphere . 282 



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