176 Mr. J. Goodman's Researches into the Identity of 



applied merely the extremity of the connecting wire against 

 the revolving cylinder. The galvanometer was deflected many 

 degrees, and considerably more than hij the friction "mth the 

 larger surface. A large surface ajjpeared to induce complex 

 results, and to destroy elementary or simple indications. 



Exp. 23. By means of a set-screw I connected the galva- 

 nometer S wire to a turning-tool, and slightly turning or sha- 

 ving off ribbons of bismuth, a considerable current was indi- 

 cated from the tool towards the bismidh. This experiment 

 with the bismuth disc and steel tool was afterwards repeated 

 by steam power, — current 40" to 45° constant, vibrated to 80° 

 or 90° at first. 



Exp. 24. With a bismuth rod against the bismuth cylinder, 

 a current of 4° and afterwards of 10° to 15° towards the cy- 

 linder was observed*. 



Exp. 25. The bismuth disc and an antimony rod gave a 

 current of 45° in the usual direction for bismuth, the anti- 

 mony robbing the bismuth. Antimony positive, bismuth ne- 

 gative. 



Exp. 26. Silver vvidi bismuth 40°. The usual bismuth 

 current. 



Exp. 27. Gold with bismuth 55°. The usual bismuth cur- 

 rent. 



Exp. 28. Lead with bismuth 27^°. The usual bismuth 

 current from the lead to the bismuth. 



Exp. 29. With an iron disc rotating under similar condi- 

 tions, I obtained, by a turning-tool of steel, a current of 10° 

 from the iron towards the tool. 



I tested the galvanometer by a voltaic pair to see the direc- 

 tion of the current, and found the direction as stated to cor- 

 respond. 



I repeateil afterwards the same experiment by steam power, 

 with a much larger cylinder of cast iron, apparently harder 

 than before, and the needle vibrated from 15° to 30°, station- 

 ary at 20° ; the current in that instance, /;o« the tool towards 

 the disc, tested by voltaic pair. 



Exp. 30. With a zinc disc and steel tool, at first no certain 

 indication of current. Repeated afterwards, with and without 

 steam power, current 3°, and afterwards 5°, constant, from 

 the tool towards the zinc. 



Exp. 31 . With the extremity of the copper connecting wire, 

 current 2%° from the zinc towards the wire. Repeated with 

 steam power, 3° towards the copper. 



May 1, 1846. With a sharp cutting edge of copper against 



* It is here seen that a preponderance is given in favour of the rod or 

 tool, botli metals being alike ; the rod is positive, the disc negative. 



