THE LEYDEN JAR. 



The " Electrophore," or " Electrophorus" we have already learned to 

 make for ourselves, as also the Leyden Jar. But we give cuts of them. 

 The former is very simple, and can be made by mixing two parts of 

 shell-lac and one of turpentine, and pouring the mixture 

 upon a metal plate. If this be rubbed with a cat's skin 

 when dry, and a metal cover with a glass handle be 

 placed upon it, it will be found that the positive and 

 negative electricity are collected on the lower and upper e 

 surfaces of the plate respectively, and can be drawn =~. I ^- J 



. f r * 1 8- 20 9- Electrophorus. 



away with a spark as before, and made use of. 



The Leyden Jar requires a little more detailed description, as it is to it 

 we are indebted for our Battery. It is a common glass bottle or jar, coated 

 both inside and out with tinfoil nearly as high as the shoulder, aa. The 

 mouth should be firmly closed with a bung of wood, gg ; a hole should be bored 

 in the bung, through which a brass rod is tightly pushed. The rod, too, is 

 topped by a brass knob, and a brass chain is attached to the 

 other extremity. The interior of the tinfoil receives positive 

 electricity, and the exterior negative when the jar is charged 

 from the " Electrophorus." To discharge the jar and create a 

 shock it is necessary to put one hand on the outside, and the 

 other on the knob of the jar. A brilliant spark and a severe 

 shock will result if the jar has been fully charged. It is as 

 well to be cautious when trying this experiment. The effect 

 of the shock may be felt by any number of persons joining 

 hands, if one at one end of the row, and one .at the other r \s- a ".The 



Leyden Jar. 



end, touch the knob and the outside of the jar simultaneously. 



This electric discharge is lightning in miniature, and it is to Benjamin 

 Franklin that the world is indebted for the discovery. The philosopher was 

 greatly interested in the science of Electricity and, having retired from 

 business, he devoted himself to the consideration of thunderstorms. He 

 wrote a treatise to show that points drew off electricity, and that electricity 

 and lightning were similar. He urged that metallic rods might be attached 

 to ships and buildings, so that during thunderstorms, or at other times, the 

 electricity might be harmlessly carried into the ground. This suggestion he 

 made without being able to explain why points did carry off electricity 

 without a spark. The reason is because there is no place to store it ; it runs 

 away at once, without having time to collect, as in a ball. 



Franklin made one or two experiments before his renowned kite-flying 

 arrangement, which convinced him that electricity was by no means an agent 

 to be played with. He endeavoured to kill a turkey by electricity, but by 

 incautious handling of the jars in which the "fluid" was stored, he dis- 

 charged them, and describes the result : " The flash was very great, and the 

 crack was as loud as a pistol ; yet my senses being instantly gone, I neither 

 saw the one nor heard the other, nor did I feel the stroke on my hand, 

 though I afterwards found it raised a round swelling where the fire entered 



