Contents xvii 



ARTICLES 



Charge of glass plates is many times greater than it ought to be by the theory . . 332 



Comparison with the globe ........... 333 



Consideration of the effects of external bodies on the globe and the plates . . . 334 



Effect of the floor and walls of the room on the charge of the globe .... 335 



Experimental investigation of this effect ......... 336 



Comparison of the charges of four rosin plates with those of circles 9^3, 18-5, and 



36 inches diameter ............ 337 



Hypothesis about the relative effect of surrounding bodies on the capacities of different 



bodies ............... 338 



Application of this hypothesis to the three circles and the globe ..... 339 



Charge of a plate of air ............ 340 



Plate of air between glass plates with tinfoil coatings 341 



Experiments with plates of air ........... 342 



Table of Results with plates of air . . . . . . . . . . 343 



Experiment to determine whether the air between the plates is charged . . . 344 



The air is not charged ............ 345 



Comparison with computed charge .......... 346 



The table agrees with the theory nearly but not quite ...... 347 



Suggested explanation ............ 348 



Three hypotheses to explain why the charge of glass plates is rather more than eight 



times what it ought to be by the theory ........ 349 



First hypothesis. Electricity penetrates into the glass to a certain depth . . . 349 



Second hypothesis. A conducting stratum within the glass. (Fig. 25) . . . 350 

 Third hypothesis. A great number of strata alternately conducting and non-conducting. 



(Fig. 26) 351 



Conduction only normal to the surface of the plate ....... 352 



Reasons for preferring the third hypothesis ........ 353 



Another reason analogy of Newton's fits ......... 354 



Effect of different degrees of electrification on the charge of a plate .... 355 



Comparison of the plate D with the circle of 36 inches diameter with two different 



degrees of electrification. No apparent alteration in capacity .... 356 



Correction for greater amount of spreading with the stronger degree of electrification 357 

 Comparison with a very weak degree of electrification. Large cylinder and wire. 



(Fig. 27) 358 



Method of the experiment ........... 359 



Result with weak electrification 360 



Comparison with the usual strength of electrification 361 



Comparison of the results ............ 362 



Discussion of the results . . . . . . . . . . . -363 



Comparison with positive and negative electrification . . . . . .364 



Accumulation at the edge is greater in plates of air than in glass plates of the same 



thickness .............. 365 



Charge of coated glass at different temperatures. (Fig. 28) 366 



The edges of the coatings kept at constant temperature 367 



Table of results at different temperatures ......... 368 



Glass conducts electricity better as the temperature rises ...... 369 



Table of the charges of glass plates .......... 370 



Table of the charges of plates of other substances . . . . . . 371 



Explanation of the tables 372 



Method of making plates of wax, &c. ......... 373 



Difficulty of making a plate of shellac ......... 374 



Dephlegmated bees wax 375 



The charge of a coated plate depends on the substance of which it is made . 376 



Difference between thick plates and thin ones ........ 377 



The thick plate of crown glass ........... 378 



