Cumming, Linnæus, b. 1843. [from old catalog] · New York, D. Van Nostrand · leaf 310
nciple. If the outer coil be free tomove, but its terminals dip into a fixed central cup and annulusof mercury, in connection with the battery, while a commutat-ing cup rotates with it, into which the terminals of the innercoil dip, the two coils will continue rotating rapidly in… … HflR^ Fig. 188. inventors to replace steam by electricity as prime motivepower. None of them have as yet come into more thanlimited use, owing chiefly to their great expensiveness com-pared with steam-engines. Thus, weight for weight, zinc isfifty times as expensive as coal, and it appears that…
Electricity
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