Chap, vii.] PTLUEGER'S TRIP-HAMMER. 



69 



production of the induced currents, to which the 

 different effects might be due. To meet and obviate 

 this o b j e c ti o n, 

 Pflueger devised 

 the trip-ham in e r 

 (Fig. 37). 



ebonite 



supports 



Tig. 37. Pflueger's Trip-Hammer. 



Aii 



stand E 



two brass up- 

 right pillars dd, 

 which carry two 

 electro-magnets K 

 K. A hammer- 

 head of soft iron 

 j is fixed at the 

 end of a steel 

 arm k, movable on an axle e. When the hammer 

 is raised, it touches the under surface of the electro- 

 magnets, and is retained by them there, provided a 

 current be passing round them to magnetise them. 

 The axle e is in connection with the binding screw c. 



O 



The hammer has a platinum-pointed brass hook m 

 attached to it, and when the head falls, owing to the 

 demagnetisation of the electro-magnets, the hook dips 

 into a cup of mercury x, which also has a binding 

 screw connected with it. a'b is a little spring-catch for 

 securely retaining the hammer when it has fallen. In 

 the front of the apparatus is a brass lever p, poised, 

 about its middle, on the axis connected with the 

 binding screw t. One end of the lever projects for- 

 wards, and rests on the screw-point R ; the other end 

 q projects behind under the hammer-head. Now, 

 suppose a current coming by a wire to R, it will pass 

 along the lever to the axle, and off by a wire at t. 

 Let, however, the hammer-head be released by demag- 

 netisation of the electro-magnets, it will fall on the end 

 q of the lever, depress it, and raise the other end so 



