Fluid Galvanic Battery. 267 



quantity of the exciting fluid. The fluid contained in the nar- 

 row part of the cell would be so small that its exciting power 

 must be exhausted in a few minutes. The annexed figure repre- 

 sents a vertical section of the best form of cast-iron i , 

 cells. The form is rectangular. The zinc plate is 

 contained in the narrow part of it ; the wide part, - 

 if it be 1~ inch high and li inch wide, will contain 

 as much of the exciting fluid as will be required for 

 a lecture of an hour or two. 



If cast-iron plates be used, earthenware or other 

 cells must be employed for holding the exciting 

 fluid, and then the outside of each cast-iron plate is inactive ; it 

 is exposed to the action of the fluid and must be protected. Ten 

 or twelve pairs of cast-iron and zinc plates may, like the copper 

 and zinc plates of a Wollaston battery, be fastened to a bar of 

 wood ; they may then be let down at once into a Wedgwood 

 trough containing the exciting fluid, and may be taken up when- 

 ever it is found necessary or convenient to suspend the action of 

 the battery. 



The great galvanic power of cast iron and zinc excited by one 

 part of sulphuric acid and two of water, was first discovered in 

 the beginning of last June. In a few days after the discovery, 

 I arranged in one series 72 cast-iron cells of our nitric acid bat- 

 tery, each containing a 4-inch zinc plate separated from the iron 

 cells by pieces of wood. They were charged with one measure 

 of sulphuric acid and two of water. The galvanic current was 

 sent through a pair of very thick coke points, each about an inch 

 long. The greater part of the coke was raised to a white heat ; 

 the result was a most brilliant light, which appeared to me to be 

 equal in illuminating power to any coke light 1 have ever seen 

 produced by an equal or much larger number of cells of the 

 nitric acid battery. There was a remarkable difference between 

 the appearance of the coke points when ignited by this battery 

 and the nitric acid battery. On this occasion the negative and 

 positive points appeared to be equally ignited and illuminated. 

 With the nitric acid battery, the positive point is much more 

 intensely ignited, and gives out a far greater quantity of light 

 than the negative one. 



At least one-third of the power of the battery just described 

 was lost: first, because the distance between the zinc and cast 

 iron was about three-eighths of an inch ; secondly, because the 

 cast-iron cells had been used several times in the nitric acid 

 battery, and were coated with nitrate of iron, which greatly 

 diminishes the galvanic power when the cast iron is excited by 

 dilute sulphuric acid. J have found by means of the galvano- 

 meter, that the power of a galvanic current produced by a cast- 



