Appleton's dictionary of machines, mechanics, engine-work, and engineering : illustrated with four thousand engravings on wood ; in two volumes (1873)
D. Appleton and Company · New York : D. Appleton and Co. · leaf 698
side, and wher-ever the rails cross each other a frog is inserted,bolted to the cross-ties. See Frog. Innumerable forms of switch-bar and frog havebeen devised for accomplishing the same purpose,and several patents have been taken out forSAvitches called safety switches, the object ofwhich is to… … of a very efiicient foim of safetj 692 TELEGRAPH. TELEGRAPH, Histonj of the. Soon after the discoTery of the Lejden jar, in 1747, it -sj-as observedthat the shock, passed through twelve thousand feet of wire, affected persons placed at either extremity,apparently at the same instant of time. The…
Mechanical engineering · Mechanics · Engineering
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