1881.] on the Phenomena of the Electric Discharge. 465 



here two iiisulatcd wires, cacli 350 yards long, coiled side by side 

 on a reel ; to the extremities of one coil is attached a platinum wire 

 six inches long and .^j inch diameter; througli the other coil I will 

 scud the charge of electricity from a condenser of seven microfarads 

 capacity (about the sixth of that just used) charged with 10,800 cells. 

 You perceive that the platinum wire is violently deflagrated with a 

 loud report by the induced current. 



The mechanical efl'ects produced by the charge of a condenser are 

 as the square of tlie number of cells used to charge it, and altliougli 

 the condenser which I have just used has only one-sixth of the 

 capacity of that I first showed you, yet its mechanical efi'ects are 

 nearly twice as great ; for the square of 10,800 is to the square of 

 ii240 as 11 to 1. lu order to show the enormous power of its charge 

 I will send it through 29 inches of platinum j^^j of an inch in 

 diameter ; this is immediately deflagrated. And if I allow the charge 

 to pass between the terminals of a discharger the loud re^iort of the 

 spark renders evident the enormous power stored up by the condenser. 

 I had hoped to show you the condenser charged with 14,400 cells, 

 but it is not capable of withstanding this potential, for one after the 

 other of the coated glass plates, of which it is made up, has broken 

 down with the charge shortly before the lecture. 



In order to afibrd you an opportunity of forming a pictorial 

 conception of that which it is wished to convey, respecting the 

 stratified discharge, I will recall to your recollection an experiment 

 often shown to you by Dr. Tyudall (Fig. 3). With a reservoir of 

 water, placed at a height of a few feet, when the taj) at the lower 

 portion is turned on the water flows out, apparently in a continuous 

 stream ; but when the thread of water is examined by means of an 

 intermittent beam of light, it is at once seen that the flow is not 

 continuous, but (in consequence of the tendency of water to assume 

 a globular form) the stream as it descends breaks up into a series 

 of drops, one following the other in rapid succession. It is not my 

 purpose here to refer to the cause of the phenomenon, which has been 

 explained to you by Dr. Tyndall in his lectures on Sound, but only 

 to recall this elegant experiment in order to present a mental picture 

 of what may occur in the aggregation of the molecules of gases 

 conveying electricity. 



Now I will cause a discharge of electricity to pass through a 

 vacuum tube containing residual carbonic acid at a pressure of 0*5 

 millim. (Fig. 4), and you will at once perceive that the residual gas 

 groups itself into a series of luminous strata, the molecules which 

 compose them being held together by the balance of electric forces, 

 whereas in the case of the water stream the particles composing the 

 globules are held together by cohesive attraction. 



The strata do not flow on like the drops of water, but remain 

 stationary ; they are, as it were, so many Leyden jars charged on one 

 side with positive and the other with negative electricity ; each imparts 

 say its positive charge to the next negative end of the succeeding 

 stratum, and receives a charge from thut behind it ; and thus the flow 



