1038 TliAXSACTTOXS OF TBE AMEHICAX IKSTITUTE. 



polarization takes place in the battery itself, and, although electric 

 motive force remains the same,, the internal resistance may be 

 increased more than a hundred times. 4. The sulphate of zinc solu- 

 tion (or any fluid about the zinc), is useful only as a conductor of 

 electricity. 5. The copper, or negative metals is Useful only as a con- 

 ductor ; since it can be replaced by any negative metal, even by zinc 

 itself. 6. The internal resistance of the battery has been separated 

 into two parts, viz. : That due to the porous cell and that due to the 

 liquids employed. The specific resistance of the liquids was found 

 to be thirteen ; that for a small clay cell seventeen, and for *a leather 

 cell seven ; since the resistance of the leather cell is less than one- 

 half that of a clay cell, we have used it in the construction of batte- 

 ries, as the quantity of electricity is nearly doubled, without any 

 increase of the surface. For the negative metal, in place of the cop- 

 per heretofore employed, we have used sheet lead. The investigations 

 have enabled us to compute with great precision the length of time 

 a battery will generate its normal quantity of electricity, provided 

 the amount of electricity flowing in the external circuit is known, 

 and the capacity of the vessel holding the sulphate of zinc solution 

 is determined. The specific gravity of the sulphate of zinc solution 

 should not be less than fifteen deg. nor more than thirty deg. Baume. 



Dr. L. Eradlcy had experimented with solutions of sulphate of 

 zinc of various degrees of density and had not found much difference. 

 There was no difference between a solution showing a density of forty 

 deg. Baume, and one showing fifteen deg. Baume. 



Mr. J. Phin. — Sheet lead has long been used for the negative 

 metal in sulphate of copper batteries; In the first work ever pub- 

 lished on the electrotype, Mr. Spencer described a battery of great 

 power, in which the negative metal consisted of thin tea lead, crimped 

 or corrugated, so that a great surface might be compressed into a 

 small space. The power of the sulphate of copper battery depends 

 largely on the amount of surface presented by the electro 'negative 

 element, and Mr. Spencer obtained this increased surface in a very 

 simple and cheap manner. In regard to the cells, clay cells vary 

 very much in the facility with which they conduct the electric cur- 

 rent. I have tested them with a galvanometer, and have found that 

 some .conduct more than twice as readily as others. Leather cells 

 have been tried, but are inferior to good clay cells. Cells made of 

 paper offer the least resistance of any, but they do not last long, and 

 they allow the sulphate of copper to pass through and attack the zinc. 



