M. E. Stohrer on an Improved Induction Apparatus. 59 



side of oue of the walls of the coil so deeply into the wood, that 

 it does not project beyond the inner surface; at the circum- 

 ference it protrudes a little. This tube receives a copper wire, 

 to which the inner end of the fine wire is soldered. The wind- 

 ing in the lathe now commences. The wire is overspuu with 

 silk and varnished before it is laid on. After the completion of 

 each layer, a mixture of 1 part of white wax and 1 part of colo- 

 phonium is laid on hot with a camel's hair pencil, and the entire 

 wire is kept warm by an alcohol lamp placed beneath it. By this 

 means all spaces are penetrated and filled with this good insula- 

 ting substance; the whole forms upon cooling a firmly con- 

 nected cylinder, which it is hardly necessary to protect from 

 external injury ; for it is known that the mixture of wax and 

 rosin is made use of as a very firm cement. The outer end of 

 the connexions is also soldered to a strong copper wire, which 

 is cemented in a small glass tube. Both ends of the wires are 

 therefore well insulated by glass, and lie far from each other ; 

 the two copper wii-es project two lines outwards, so that binding 

 screws may be readily attached to them. 



All three coils are wound in the same manner and in the same 

 direction ; they are so pushed on to the interior spiral that the 

 ends of all the interior wires stand on one side, while all the 

 externa] ends are at the other, in a vertical direction. The 

 manner of uniting the wires by intervening pieces will be mani- 

 fest from the figure. The lowest coil rests upon three small 

 pillars of ivory, which are not seen in the drawing. From the 

 upper and under ends of the system of coils the wires are car- 

 ried directly to the discharger. 



3. The interruptor E is placed upon a wooden foot, and may 

 also be made use of for other purposes ; as it can be taken away 

 at once after the connecting wires have been removed. An 

 electro-magnet, round which four layers of the same double 

 wire which is used in the inner spiral are coiled, acts on a per- 

 forated and grooved iron cylinder F. The latter is attached 

 to a strong lever, H, which is drawn downwards by a spiral 

 spring. The platinum point of the screw H at the extreme 

 end of the lever presses forcibly on the upper portion of a 

 strong copper spring, J. On the upper surface of the spring 

 is placed a disc covered with platinum, which can be caused to 

 rotate, and is touched by the platinum point, not at the centre, 

 but somewhere between the centre and circumference. This is 

 for the purpose of changing at pleasure the point of contact 

 without filing, which would be necessary if the platinum were 

 fixed. 



Under the projecting portion of the spring J (here is a screw 

 L, which, where it rises, supports the spring so that the latter 



