Figure 3. — Volta's "crown of cups" (at top) and his voltaic pile. From Philo- 

 sophical Transactions oj the Royal Society of London, 1800, vol. 90, plate opposite 

 p. 430. 



experimenter had "to hasten to complete his experi- 

 ments before the power had materially declined." " 

 Two years later William Pepys built two troughs (fig. 

 9) with 130 pairs of zinc and copper plates, each plate 

 being 6 inches square.^" Each trough was charged 



' Benjamin Silliman, First Principles oJ Chemistry, Philadelphia, 

 1847, p. 115. 



If William Cruickshanks, "Description of Mr. Pepys' Large 

 Galvanic Apparatus," Philosophical Magazine, 1803, vol. 15, 

 pp. 94-96. 



with dilute "nitrous acid." In 1807 Humphrey Davy 

 used three such batteries to separate sodium and 

 potassium frorn their compounds. '' One battery had 

 24 pairs of copper and zinc plates 12 inches square; 



n Humphrey Davy, "On Some New Phenomena of Chemical 

 Changes Produced by Electricity, Particularly the Decomposi- 

 tion of the Fixed Alkalies, and the Exhibition of the Nevvf 

 Substances which Constitute Their Bases; and on the General 

 Nature of Alkaline Bodies," Philosophical Transactions, 1808, 

 vol. 98, pp. 1-44. 



236 



BULLETIN 228 : CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



