on the Construction of a Voltaic Appda-atus. 29 



small battery proves the utility of having the cells of suf- 

 ficient capacity to hold a large quantity of liquor, by which 

 much trouble of emptying and filling the troughs is avoided, 

 and the action, kept up, without intermission, for a long 

 space of time, — a circumstance, in many experiments, of 

 material consequence. Besides this advantage, svith very 

 large combinations, a certain distance between each pair of 

 plates is absolutely necessary, to prevent spontaneous dis- 

 charges, which will otherwise ensue, accompanied willi vivid 

 flashes of electric light, as I have experienced, with a bat- 

 tery of 1250 four-inch plates, on the new construction. 

 And here I beg leave to mention an experiment, which, 

 though not directly in point, cannot be considered as foreign 

 to the subject of this paper. It has been urged, as one proof 

 of the non-identity of the common electricity, and that given 

 out by the Voltaic apparatus, that in the latter there is no 

 striking distance. That objection, however, must cease. 

 I took a small receiver, open at one end ; through perfora- 

 tions in the opposite sides of which were placed two wires, 

 with platina points, well polished : one was fixed by cement 

 to the glass, the other was moveable, by means of a fine 

 screw, through a collar of leathers, and the distance be- " 

 tween the points was ascertained by a small micrometer at-** 

 tached. This receiver was inverted over well dried potash 

 over mercury, and suffered to stand a couple of days, to de- 

 prive the air it contained, as thoroughly as possible, of 

 moisture. The 1250 plates being excited precisely to the 

 same degree as the great battery, mentioned in the beginning 

 of this communication; and the little receiver placed in the 

 circuit, I ascertained its striking distance to be ^-'o*'' "^ <*n 

 inch. That I might be certain that the air in the apparatus 

 had not become a conductor by increase of temperature, I 

 repeated the experiment several times with fresh cool air, 

 and always with the same result ; but perhaps it will be ob- 

 jected, that the striking distance was so small, as not to 

 afford a satisfactory refutation of the argument alluded to, 

 when it is considered to how very great a distance, com- 

 paratively, the spark of the common electrical machine can 

 pass through air. The answer to this is obvious : incrcasa 



the 



