60 M. E. Stohrer on an Improved Induction Apparatm. 



loses its property of yielding, the descending lever thus meeting 

 a firm surface below. Besides this, between the limbs of the 

 spring a bit of cork is fixed for the purpose of damping the 

 vibrations, which are not favourable to the development of the 

 induced current. Finally, there is another screw K, by the 

 turning of which a greater or less degree of tension may be 

 imparted to the spiral spring. With this arrangement of the 

 interruptor, we are able to fulfil, as completely as possible, the 

 conditions which are necessary to the development of a powerful 

 induced current. 



When the making and breaking of the primary circuit is 

 effected by the hand, by bringing the wires into contact, and 

 then separating them quickly, one is soon convinced that the 

 stronger the wires are pressed together before separation, and 

 the more suddenly they are separated, the greater are the 

 sparks which cross at the ends of the induction coil. It 

 is just the same with the contact and separation of the platinum 

 point and plate. The largest sparks are obtained when the 

 spiral spring is in a state of the strongest tension, and the 

 iron armature is not permitted to come too near to the electro- 

 magnet ; for a portion of the force would be thus neutralized 

 with which the lever is pressed by the spiral spring against the 

 platinum plate. 



Further, it is not indifferent whether the platinum point of 

 the screw H meets at the closing of the circuit with a firm or a 

 yielding surface ; for in the first case the current will circulate 

 only for a very short time, and the duration of the interruption 

 will be greater than that of the closure of the circuit ; in the 

 latter case, on the contrary, where the spring J yields, we have 

 a longer closure, and a time of interruption shorter or longer 

 according to circumstances. By the use of the three screws 

 H, L, and K, this relation can be altered at pleasure, and the 

 play of the lever also permitted to proceed more slowly or quickly. 

 It is very interesting to observe the dependence of the induced 

 current upon the manner of closing or breaking the primary 

 current ; and it is not to be wondered at, that in experiments 

 where the separation has been effected between other metals, as 

 silver, copper, gold, &c., such great differences should have been 

 observed. 



4. The discharger merely ministers to the convenience of the 

 experimenter ; it has however also the effect of preventing too 

 great a condensation of the electricity in the spirals, neutraliza- 

 tion being effected by the passage of the sparks. 



Two small bars of steel move in the stands C and D, which 

 are insulated by glass pillars. The bars are furnished at the 

 hinder extremities with discs of brass, and at the forward cxtrc- 



