260 Electricity and Galvanism, 



required. After devoting some attention to the subject I contrived 

 the machine before you, which answers the purpose most completely. 

 It consists of the double coils of wire fixed in a wooden box, on the lid 

 of which is placed a wooden cylinder, capable of revolving between 

 two uprights by means of a proper handle. This cylinder is furnish- 

 ed with two slips of brass fixed in the wood at each end, and connected 

 with the metallic axes, by which the cylinder is supported in the brass 

 collars of the uprights. The slips of brass are placed so as to alter- 

 nate with each other at either end of the cylinder. Two electric 

 brass springs, supported by pillars of that metal, press on the cy- 

 linder at either end. The ends of the thick wire of the coil con- 

 cealed in the box are connected, — one to the end of one of the 

 supports of the cylinder, the other to a binding screw fixed in the lid. 

 The zinc and silver plates of a single battery are then connected with 

 this screw, and with the supports of one of the brass springs. On 

 revolving the cylinder, contact with the battery is of course made or 

 broken according as the slip of brass or the wooden portion of the 

 cylinder passes under the brass spring. You know that with each 

 of such unions and ruptures of contact, an induced current circu- 

 lates in the fine coil of wire in the box. The ends of this coil are 

 soldered to the second upright, and the support of the second spring. 

 The pieces of brass being properly arranged, it follows that one kind 

 of current can alone traverse the conducting wires fixed to the sup- 

 ports connected with the fine coil. To prove this, I will let these 

 conductors, terminated as before with platinum ends, rest on the 

 iodized paper. On turning the cylinder, the iodine is, as you see, 

 set free at one end only. I know, therefore, that the positive elec- 

 tricity escapes by this wire, and the negative by the other. Hence 

 by this instrument we have succeeded in detaining separate currents, 

 although we have lost the great convenience of the automatic move- 

 ment of the other apparatus. 



I purpose, next, to direct attention to the results which have fol- 

 lowed the employment of the different modifications of electricity in 

 the treatment of disease. In doing this I do not intend to occupy 

 your time by a tedious reference to all that has been previously pub- 

 lished on this subject in this country and on the continent. Such 

 records are familiar to every physician, and within the reach of every 



