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46 Prof, dimming on a new Thermoelectric Instrument. [Jan. 



Article IX. 



Description of a New Thermoelectric Instrument. By the Rev. 

 J. Gumming, Professor of Chemistry in the University of 

 Cambridge. 



(To the Editor of the Annals of Philosophy.) 

 MY DEAR SIR, Cambridge, Dec. 20, 1823. 



Whatever contributes to confirm the close analogy which 

 subsists between the electricity excited by heat and that by 

 galvanic action, will, I conceive, be acceptable to those who 

 take an interest in this subject. For this purpose, I have con- 

 structed an instrument, the description of which you will oblige 

 me by inserting in the next number of the Annals of Philosophy. 

 It exhibits the rotation of a wire round a magnet, and its deli- 

 cacy is such that when excited by the thermoelectricity of a 

 silver and platina wire, each of l-22d inch diameter, it revolves 

 between 30 and 40 times in a minute ; if, instead of these wires, 

 a pair of galvanic plates of half an inch in diameter be used, the 

 rotation is rather more rapid. 



1 am, my dear Sir, very truly yours, 



J. CUMMING. 



A B, a cylindrical magnet. 



abed,* glass tube containing mercury, cemented on the top 



of the magnet. 



CDEF, a brass wire poised by a needle point passing 

 through I, and resting upon an agate cemented upon the 

 magnet. 



