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Dr^ Harems Defiagrator and Calorimotor. 103 



In the trials made last October with your instrument, the 

 coils were used without glasses, being immersed in a fluid^ 

 contained in a common recipient. In those recently per- 

 formed, and which I shall now relate, the metallic coils 

 were individually insulated, for they were immersed in the 

 cylindrical glasses belonging to the apparatus, it being pre- 

 viously connected with the common galvanic battery by its 

 proper poles as described in my former letter; the effects 

 were however in no respect different from those before ob- 

 served, so that the insulation of the coils appears to be a 

 fact of no importance. In the first experiment the deflagrator 

 being connected by its proper poles with a galvanic batte- 

 ry of 300 pairs of four inch plates cemented in mahogany 

 troughs, and interposed between the two rows of the de- 

 flagrator, of forty coils each, lost all its power, and the ef- 

 fect produced was very much inferior to that of the battery 

 alone, for in fact the spark was hardly perceptible- 



The chemical or decomposing powers of the common 

 galvanic battery, were also found to be suspended by the 

 connexion — for the 300 pairs which usually decompose wa- 

 ter, salts, &:c. with decisive energy, now produced in water 

 scarcely a bubble of gas, and hardly affected dilute infusion 

 of purple cabbage. The power of giving a shock was also 



destroyed by the connexion. 



When the coils were raised out of the fluid and suspend- 

 ed only in the air, they acted as conductors of the power of 

 the common battery, which now produced all its appropri- 

 ate effects, although, even in this case, the galvanic influ- 

 ence appeared soniewhat diminished, which would of course 

 arise both from the extent of the conducting surface, and 

 from the fact that a part of the substance, namely, the 

 wedges of moist wood, interposed between the metals was 

 an imperfect conductor- 



These experiments (including the former trials) were 

 niade with different combinations from 620 pairs down to 

 20, and were attended, uniformly with the same result; viz. 

 an almost entire suspension of the power of both instru- 

 ments. 



In one of the experiments, twenty-five pairs of the zinc 

 and copper plates, six inches square, connected by slips of 

 copper and suspended from a beam of wood were immers- 

 ed in a trough without partitions filled with an acid liquor, 

 and the connexion bein^ formed with the deflagratorj the 



