56 M. E. Stcihrer on an Improved Induction Apparatus, 



a good many of the little bars may be removed from the spiral 

 without weakening the induced current; this was particularly 

 the case when the condenser was introduced. 



But although the horseshoe form of the electi-o-magnet above 

 mentioned did not produce the desired effect, one advantage of 

 this arrangement remains valuable, that is, the use of the in- 

 terrupter. 



When a strong iron or steel spring is fastened to one pole, 

 and reaches closely over the other, terminating there in a piece 

 of iron of the shape of a hammer, this serves as a continuation 

 of the magnet, and will be very strongly attracted by the other 

 pole. Nearly in the middle of the spring is placed a piece of 

 brass coated with platinum ; above the latter, upon a stand, is 

 the regulating screw with its platinum point, which carries the 

 current from the battery to the spring and to the commencement 

 of the primary coil. The vibrations of this strong spring are 

 very energetic : they effect a sure closing and an exact interrup- 

 tio]i of the circuit. 



Upon each limb of the horseshoe magnet, the wire of which 

 had been previously protected by a coating of strong gutta-percha, 

 stands an induction coil, the body of which, consisting of wood, 

 was also coated with gutta-percha previous to the winding of the 

 wire. The interior end of the fine wire is carried outwards 

 through a glass tube. Each coil has an interior diameter of 45 

 millims. The windings reach to a height of 120 millims. ; 

 the exterior diameter of the coil is 85 millims. As the horse- 

 shoe magnet stands vertical, both ends of the spirals are carried 

 upwards through the wood of the spiral, and terminate in insu- 

 lated binding screws, which may be conveniently combined both 

 together or in succession. By an arrangement for discharging, 

 the distance which the sparks are to pass over can be altered 

 at pleasure. 



The whole of the phjenomena hitherto known may be seen at 

 the discharger ; as, however, I did not succeed until afterwards 

 in the construction of a good condenser, the striking distance of 

 the sparks in air was not very considerable, although the appear- 

 ances in i-arefied air were very beautiful, and accompanied by all 

 the peculiarities already so often described. 



For the experiments in vacuo I did not use the so-called elec- 

 tric egg, that is, the ellipsoidal receiver, but a glass jar, 15 inches 

 high and 5 inches in diameter, which could be closed above with a 

 stopper, and conveniently placed on the plate of the air-pump; it 

 was more easily cleaned than the egg. Besides this, in order to 

 make the whole apparatus more portable, I have constructed for 

 the experiments a suitable hand air-pump, which maybe exhausted 

 to at least 1 millim. barometric pressure, and which is also useful 



