Electricity and Galvanism. 



257 



quantity and intensity of the inductive electricity, together with the 

 additional recommendation of low price. 



A. The wooden bobbin, on which is wound the double coil of wires. 



B. C. The screws connected with the ends of the fine coil, with conductors 



affixed. 



D. The apparatus for breaking battery contact. 



E. Single pair of plates (Smee's arrangement) connected with the screws, 



F. G. 



This consists of a wooden bobbin, with a hollow axis. About thirty 

 feet of thick insulated copper wire are wound on it, and over this 

 about a thousand feet of very fine insulated copper wire, the ends 

 of which are soldered to a couple of binding screws fixed in the base 

 of the instrument : the former is the coil in which the initial or 

 inducing current is intended to circulate ; the latter is the secondary 

 coil, where electricity is to be disturbed and thrown into motion, 

 to form the induced current. One of the ends of the primary 

 thinner coil is connected with the zinc plate of a single battery ; the 

 other end of the wire surrounds a small horseshoe of soft iron, and 

 is then soldered to the lower end of a bent rod of brass, whose upper 

 end carries a small screw furnished with a platinum point, which 

 presses on a plate of the same metal fixed to a transverse bar of thin 

 brass, having at the end suspended over the poles of the horseshoe 

 a disk of soft iron. When the fixed end of this bar is connected 

 with the copper or silver plate of the little battery, the disk of iron 

 is rapidly attracted by the ends of the horseshoe, which acquire 

 a powerful magnetic force. In an instant, the contact between the 

 platinum wire and plate being broken, the current is arrested, and, 

 the horseshoe losing its magnetism, the elasticity of the brass bars 



2 L 



