m 



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Figure 17. — Battery of Daniell cells as used in American telegraphy. From 

 G. B. Prescott, History, Theory, and Practice of the Electric Telegraph, Boston, 

 i860, p. 27. 



Figure 18. — Meidinger's three forms of the Daniell cell. From T. Karass, 

 Geschichte der Telegraphie, Braunschweig, igog, p. 68. 



244 



BULLETIN 228 : CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



