[24] See Researches in Telephony.—Trans. of American Acad. of Arts and Sciences, vol. xii. p. 1.
[25] Elisha Gray. Eng. Pat. Spec. No. 2646, Aug. 1874.
USEFUL BOOKS ON TELEGRAPHY, &c.
Just published, Parts XIII. and XIV., in one vol. demy 8vo, sewed, 5s.
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