Experiments and Inductions. 201 



increase for a certain distance, obtain a maximum, and then di- 

 minish. Generally it must be in a continual state of change 

 according to the varying condition of the system to which it 

 belongs. 



61. In the magic pane the free part of the charge compresses 

 the engaged part by the contractile tension of the free lines. 

 These by their lateral repulsion tend to fill up unoccupied space, 

 and thus bend round the engaged lines and acquire the lateral 

 packing power by their longitudinal tensile force when thus bent. 



Fig. 40 is intended to give an idea of the charging of a magic 

 pane. The line B pressed forward by A (intended to represent 

 the lines engendered by the machine) arrives at the balls k, I. 

 The ball / cuts the line, and so do the opposite surfaces of the 

 magic pane. The part of it between k and I remains, and so 

 does the part between the coatings of the magic pane. The 

 part c between I and the near surface of the magic pane con- 

 tracts and discharges itself along the conducting wire w, the 

 exterior part D escapes to the ground by the free conductor x 

 after the centre part N has been pressed into the magic pane. 

 The lines between k and / accumulate until discharge takes 

 place, which may be looked upon as a signal that a certain 

 number a of lines have crossed over and left segments packed 

 into the magic pane. The spark appears after the unit quantity 

 has entered the jar. The propelling force (from the machine) 

 required to bring up a of course increases as the charge M 

 increases ; but when brought up, it is probable that discharge 

 between k, I destroys the same constant number of lines, and 

 thus that the unit-jar correctly measures quantity, its coatings 

 i,j being viewed as prolongations of the surfaces of the respec- 

 tive balls. 



Remarks. 



In experiments such as 1, 3, 5, 6, the phenomena are, strictly 

 speaking, examples of convection or conveying of polarized par- 

 ticles (except 56, 5c) to non-conducting matter, upon which they 

 adhere without being depolarized. They all tend to prove that 

 electricity is never separate from matter even in discharge. 



(3.) It seems probable (since a small ball throws off stars) 

 that a brush consists of a symmetrical succession of polarized 

 molecules — at least when discharged upon a non-conducting 

 surface, upon which they cling still in an excited condition, and 

 therefore must act repellent upon the next in succession (see 4) . 

 The breadth of the fosse is evidently caused by capillarity. 



(7.) In this experiment the thin shell-lac coating of the con- 

 ductor becomes charged as magic pane with one side only 

 coated. Viewed in the dark, the brush was of eccentric forms. 



(8 a.) Is a remarkable effect that I do not recollect having seen 

 Phil. Mag. S. 4. Vol. 29. No. 195. March 1865. P 



