w 



N" 



Tin; 



ARTICLE XII. 



Engraving and Description of a Rotatory Multiplier, or one in which 

 one or more Needles are made to revolve hy a Galvanic Current, 

 By R. Hare, M. B., Professor of Chemistry in the University of 

 Pennsylvania. Read December 7, 1838. 



The preceding engraving represents a rotatory galvanometer, or mul- 

 tiplier, which I contrived in November 1836, and which must have 

 value as an addition to the amusing, if not to the useful implements of 

 science. It is well known that by passing a temporary discharge 

 through the coil of a multiplier, the needle may be made to perform a 

 revolution, whereas if the current be continuously applied, the move- 

 ment is checked as soon as the situation of the poles is reversed. To 

 produce a permanent motion, the discharge must be allowed to take 

 place only when the poles are in a favourable position, relatively to the 

 excited coil. This object I attained by means of two pins, descending 

 from the needle perpendicularly, so as to enter two globules of mer- 



VI. — 4 L 



