Dr. Hare's Dcjiagrator 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 recentlj' per- 

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

 were individually insulated, for they v/ere 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, tlie galvanic influ- 

 ence appeared somewhat 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 

 made 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 being formed with the deflagrator, the 



