DOVE ON THE ELECTRICITY OF INDUCTIOX. 167 



clamped, to the axis of the keeper, and by means of that to 

 the cylindei' Wg (fig. 7)j '^ is a connecting wire from the left-hand 

 plate passing underneath to the cylinder ?t'j, with which the end a 

 is directly connected. The portion cut out of the copper disc 

 is supplied by ivory. In the position of the handle to the right 

 in the first figure, this plate of ivory is exactly below the copper 

 plate under which n is clamped, consequently the commence- 

 ment only of the right-hand wire coil a. is in connexion with the 

 cylinder Wj ; the end /3 by means of the right half of the copper 

 disc is connected with the commencement of the second spiral a, 

 whose end b is brought into conducting connexion with the cy- 

 linder ^2 by means oip. This connexion is therefore n a. ^ abp, 

 i. e. both coils are connected one behind the other. In the 

 second figure, on the contrary, « is connected with a by means 

 of the left half of the copper disc through the wires, which cross 

 each other mthout touching, /3 by means of the right half is con- 

 nected with b ; the connexion is therefore n I „ >p ; the cur- 

 rents of both coils are therefore united with each other as well 

 on entering as on leaving them. 



69. Suppose in fig. 7 the pachy trope fixed to the base of thekeeper, 

 the cylinders w^ and w^ removed, as also the supports E,F,G,and 

 likewise the springs proceeding from them and the extra spiral, we 

 have then Saxton's machine with the improvements of M. Oert- 

 ling. For the purpose of making the following experiments I have 

 added the parts just mentioned. In this form the apparatus can 

 be recommended as a very convenient instrument for demonstra- 

 ting the action of the extra current at the commencement and end 

 of a primary current. The support E is intended to effect the in- 

 sertion of the spiral for producing the extra current. The cylinder 

 i»i is connected with the spiral through the spring pi'oceeding to 5) 

 by means of the wire S clamped at 6). The connexion then pro- 

 ceeds further through 1) and 3) by means of the intermittent spring 

 to the cylinder w^. The two other supports Fand G, as well as the 

 cylinder iv^, are only used for the purpose of showing the sparks 

 of the secondary current, and will be noticed hereafter, § 83. The 

 cylinder w^, constructed upon the principle of a lightning-wheel 

 or mutator, presents eighteen interrui^tions to the intermittent 

 spring 3). It is used for the purpose of rendering perceptible 

 the increase and decrease of the physiological action during one 

 w hole revolution of the keeper. The cylinders w^ and w^ are fixed 



VOL. V. PART XVIIJ. .V 



