ACCUMULATORS. 87 



of an inch in diameter, and 25 feet long, melted into 

 globules; and tin wires, -fa of an inch in diameter, and 

 8 inches long, dissipated in smoke. 



Tyndall accidentally received a charge from a Ley- 

 den battery of " fifteen large jars " during a lecture, 

 and describes his experience as follows : " For a sensi- 

 ble interval life was absolutely blotted out, but there 

 was no trace of pain. After a little time consciousness 

 returned; I saw confusedly both the audience and the ap- 

 paratus. But though the intellectual consciousness of my 

 position returned with exceeding rapidity, it was not so 

 with the optical consciousness. For my body presented to 

 my eyes the appearance of a number of separate pieces. 

 The arms, for example, were detached from the trunk 

 and suspended in the air. In fact, memory and the 

 power of reasoning appeared to be complete long before 

 the restoration of the optic nerve to healthy action." 



Gunpowder cannot be exploded by the ordinary 

 discharge; the only effect of which is to scatter it. But 

 when the discharge is retarded, by introducing into the 

 circuit an imperfect conductor, as a wet string, it 

 explodes readily. By this method also gun-cotton, 

 phosphorus, and other highly inflammable substances 

 may be ignited. 



For such experiments the universal discharger, rep- 

 resented by Fig. 25, is convenient. It is constructed 

 with a base, in the center of which, mounted on a stem, 

 is a small circular tablet of some insulating material, as 

 ebonite ; and at each end, mounted on insulating stems, 

 are brass sliding rods, each terminating in balls, and 

 passing through a socket hinged on the top of its stem. 

 A plaster of paris receptacle, to hold inflammable 

 substances, should also be provided. 



