2OO 



SCIENTIFIC RECREATIONS. 



insert into the glass a tea-spoon, and if all the articles are quite dry we 

 shall possess a Ley den jar. 



To charge the jar we have thus provided we must work the Electrophortis 

 we have already described. While one person lifts off the paper as 

 directed, another must hold the glass filled with shot close to the edge of 

 the tray, and touch the corner with the tea-spoon ; the spark will then enter 

 the "jar" or tumbler. We can thus charge the jar as we please, and by 

 presenting the finger as in the illustration (fig. 202), we shall obtain a dis- 

 charge from it. 



Mr. Louis Figuier, in his " Merveilles de la Science? relates that Wol- 



Fig. 202. A Leyden jar. 



laston, meeting one of his friends one evening in the streets of London, 

 drew from his pocket a copper thimble, and proceeded to turn it into a 

 microscopic pile.* 



In order to do this he removed the bottom of the thimble, flattened it 

 with a stone, so as to bring the two internal surfaces about on a line with 

 each other, then placed between the copper surfaces a small strip of zinc, 

 which was not in contact with the copper, owing to the interposition of a 

 little sealing-wax. He then placed it in a glass cup, previously filled with 

 the contents of a small phial of water, acidulated with sulphuric acid. He 



* This interesting experiment, which we have exactly verified, was described to us by 

 Professor Waldner, and M A. Keppler. 



