1881. J Phenomena of Electric Discharge. 491 



INDEX 



I'AG !•. 



Arc — distance at wliich an arc forms with various potentials : 



Between two points, length as the squares of the number of cells . . 4G9, 470 



In rtuence of form of point on length of spark 47G 



of metal used for point on length of spark 477 



Between point and disc (sa' (iuj^m/n) 470 



Variation in, according as the point is negative or positive with a low 



or high potential 476 



Between two discs (se^ (f«a(7raAn) 470 



two spherical surfaces (^see diagram) 470 



Stratification of 467, 4G8 



AlROKA BOREALIS 475,476 



Battery, chloride of t^ilver, in principle same as Daniell's ; but in it the 

 soluble sulphate of copper is replaced by the insoluble chloride 



of silver 471 



Construction of 471,472,473 



Electromotive force of, about a volt 472 



Time requisite to make the special battery of 14,400 cells used at 



lecture 489 



occupied in charging it , . 489 



Blcxjks of Light and Strata — the molecules which compose them are 



held together by the balance of electric forces 465 



Condenser— current necessary to charge a condenser of 42*8 microfarads 464 



Davy, Sir Humphry, his battery of 2000 cells at the Royal Institution 463 



Deflagration of Wires, by primary current 464 



by secondary current 465 



Dilatation of Gases, sudden, on causing a discharge in closed 



vessels .. 481,482,483 



Dhcharge preceding the formation of arc, character of 477,478 



Discontinuity of 479 



Disruptive nature of, in vacuum tubes 483 



, in deflagrated wires 464 



Discharger, Micrometer- 469 



Faraday — his estimate of the quantity of electricity necessary to produce 



a lightning flash ' 464 



Gassiot — battery of 3000 cells 463,464 



Heat developed in a vacuum tube greatest in vicinity of strata .. ,. 486 

 Hyperbolic Curve represents the experimental results of the discharge 

 between discs at a constant pressure and various distances and 

 potentials, or at a constant distance and various pressures and 

 potentials 471,472 



Intermittent Static Spark produced by introduction of resistance .. 479 



