DISCOUESE OF W. B. TAYLOR. 215 



this science, with the least expense of galvanism, evidently requires 

 some additional modification of apparatus, and particularly in those 

 cases in which powerful magnets cannot be applied. And such a 

 modification appears to me to be obviously pointed out in the con- 

 struction of Professor Schweigger's Galvanic Multiplier: the prin- 

 ciples of this instrument being directly applicable to all the experi- 

 ments in which Mr. Sturgeon's improvement fails to be useful." : 



The coils employed in the various articles of apparatus thus 

 improved, comprised usually about twenty turns of fine copper wire 

 wound with silk to prevent metallic contact, the whole being closely 

 bound together. To exhibit for example Ampere's ingenious and 

 delicate experiment showing the directive action of the earth as a 

 magnet on a galvanic current when its conductor is free to move, 

 (usually a small wire frame with its extremities dipping either into 

 mercury cups, or into mercury channels,) or its simpler modifica- 

 tion, the "ring" of De la Rive, (usually an inch or two in diam- 

 eter and made to float freely with its galvanic element in its 

 own bath,) the effect was strikingly enhanced by Henry's method 

 of suspending by a silk thread a large circular coil twenty inches 

 in diameter, of many wire circuits bound together with ribbon, 

 the extremities of the wire protruding at the lower part of the 

 hoop, and soldered to a pair of small galvanic plates; when by 

 simply placing a tumbler of acidulated water beneath, he caused the 

 hoop at once to assume (after a few oscillations) its equatorial posi- 

 tion transverse to the magnetic meridian. By a similar arrangement 

 of two circular coils of different diameters, one suspended within the 

 other, Ampere's fine discovery of the mutual action of two electric 

 currents on each other, was as strikingly displayed. Such was the 

 character of demonstration by which the new Professor was accus- 

 tomed to make visible to his classes the principles of electro-magnet- 

 ism: and it is safe to say that in simplicity, distinctness, and 

 efficiency, such apparatus for the lecture-room was far superior to 

 any of the kind then existing. 



Should any one be disposed to conclude that this simple exten- 

 sion of Schweigger's multiple coil was unimportant and unmeri- 

 torious, the ready answer occurs, that talented and skillful electri- 



* Trans. Albany Institute, vol. i. pp. 22, 23. 



