Eaat and Westy ti'aver^ed Inj an J^Jlcclric Current. o2D 



tlic result expected and sono-]it for is, I believe, to bo found 

 in the relative lengths of the horizontal and vertical portions 

 of the movable wire he employed. He does not state these 

 lengths directl}^ for the experiment in which the wire was 

 suspended to a lever-arm, but says, " I bent a wire twice 

 at right angles, as in the first experiment described in this 

 note, and fastened on to each extremity a short piece of thin 

 wire amalgamated ;" and from the description of this first 



experiment it appears that " a piece of wire fourteen inches 



long, had an inch at each extremity bent at right angles ; " 

 so that probably, v/ith the pieces of finer wire attached, the 

 turned-down ends may have been each a couple of inches 

 long, while the horizontal portion was only twelve inches, 

 thus making the ratio of the vertical portion of the movable 

 current to the horizontal perhaps =1:3, while in my appa- 

 ratus this ratio, measuring the turned-down ends of wire to 

 the surface of the mercur}^, = about 1 : 40. In a subsequent 

 experiment to examine the nature of the action which he had 

 noticed between the copper wire and the mercury, Faraday 

 seems to have relatively shortened the horizontal portion of 

 the wire, making it only two inches long; and he then ob- 

 tained much increased rise of the wire on establishing the 

 current. 



It was apparently the opposite step, viz. relatively increasing 

 {he length of the horizontal wire that was needed to so reduce 

 the disturbing influence as to enable the effect of the earth's 

 magnetism, as originally sought, to be observed*. 



There is, of course, nothing new in principle in the experi- 

 ments above described, the results following directly from 

 what are admitted on all hands as the laws of electro-magnetic 

 action ; but it is alwa^^s interesting to verify for the first time 

 l^y direct observation any consequence of such well-established 

 laws, and I have been unable to find any record of other 

 work on this particular point except the incomplete, and in 

 a sense unsuccessful, experiments of Faraday which have 

 been quoted. 



University of Yirginia, 

 September 5, 1877. 



* I have found tliat, making the turned-duv, n ends quite sliort, the 

 experiment may he made to give fairly ohservable results with a single 

 wire not more than a metre in length. 



