On Electric Phenomena. 25 



In cases where less power is necessary, the electro-magnetic 

 machine can be used. The most important, because it is 

 much required in science, is the little machine, which the op- 

 tician Wagner in Frankfurt on the Maine has invented, and to 

 whom the German Confederation promised one hundred thousand 

 guldens, if he could construct an electro-magnetic engine. He 

 was not able to construct the engine, but the little apparatus 

 which he invented on this occasion, has made his name im- 

 mortal. It is called after him Wagner's Hammer. 



A Httle electro-magnet stands perpendicularly, and above 

 it swings an iron anchor which is fastened to a lever. The 

 lever is pressed by means of a spring against a platina spike 

 and the current of the chain is so arranged, that it goes from 

 the lever to the platina spike, from thence to the coils of the 

 electro-magnet, and then back again to the chain. Through 

 that the magnetism ceases, the anchor is no longer attracted, 

 and the spring again presses the lever against the spike. Now, 

 if the current be again closed, the anchor will be again at- 

 tracted and the current interrupted, and thus the apparatus 

 continues in play, as long as the chain has a current to de- 

 velop. 



Dr. Siemens has made a very ingenious application of 

 this apparatus, in telegraphy. It is, however, especially ap- 



I plied medically, to stimulate the muscles and nerves. The sti- 

 mulus takes place at the moment, in which the current is 

 closed and interrupted. It is, like the closing and opening, 

 I only of short duration. If the stimulus should last longer, 

 then the closing and opening of the current, must be succes- 

 sively repeated, which can best be effected by Wagner''s Ham- 

 mer. It is, however, much more expedient to use for the 

 purpose of stimulation, such currents which only last for a 



1872. II. 1. (147) c 



