OF ARTS AND SCIENCES. 207 



electricity ; that tliere is no evidence of any polarity ; tliat the force 

 passes through ordinary insulators hettcr than electricity of hi^fli 

 tension ; that no physiological effects are manifested when tlie dis- 

 charge is received by the hnnian body, and that it is impossible to 

 charge a Leyden jar or to affect a sensitive electrometer or mirror gal- 

 vaiionietcr by this force. The spark, it is c-laimed, differs from that 

 of ordinary electricity of high tension, in that it recjuires contact of the 

 end of the wire conducting it with a metal or carbon point presented 

 to it. The best sparks were obtained by rubbing a fine iron wire 

 against a rusty ffle or stove-pipe. Dr. Beard found that a galvano- 

 scopic frog gave no evidence of the existence of the force, although 

 a spark was received after the passage of the force through the frog. 

 I\Ir. Edison passed the force through iodized paper for three hours, 

 and no effect was produced. He also took the wire connected with 

 the apparatus out of doors, ran it along the ground and in a ditch on a 

 rainy night, and brought it upstairs several rods from the battery, and 

 the spark was seen by himself and Dr. Heard, at the terminal of the 

 carbon point connected with the wire. 



The apparatus which I used to produce the phenomenon was a 

 strong electro-magnet, the limbs of which were six inches long, and 

 were covered with large bobbins of coarse wire, having a resistance 

 each of .70 of an ohm. Bars of iron, steel, and brass, were used as 

 armatures to evolve the force ; a copper wire was connected with the 

 bar of metal at various places, sometimes at the end and sometimes 

 in the middle ; and the end of this wire was tested by one of Sir Wil- 

 liam Thomson's cpuidrant electrometers, by his most delicate mirror 

 galvanometer, and by the carbon points advised by Dr. Beard in his 

 letter which we have referred to at the opening of this article. 



The electrometer immediately showed a slight tension on the sur- 

 face of the bar of metal, which constituted the armature of the electro- 

 magnet. By the method of multiplication, the swing of the needle was 

 increased, so as to give uiunistakable indications of polarity ; the 

 directions of the indication being in opposite directions at making and 

 breaking the circuit of the electro-magnet. 



It was evident that the want of polarity noticed by Mr. Edison was 

 due to the rapid alternating nature of the induction currents produced 

 in the bar of cadmium. That this so-called etheric force was nothing 

 but a phenomenon of induction seemed evident at first sight ; but one 

 would hardly have predicted that currents of sufficient intensity could 

 have been created in this way to produce a spark. The phenomenon 

 possesses, however, considerable interest, which seems to have been 



