. Railway master mechanic . ing on a horizontal bar, this carrier being providedwith a marking point which bears upon a thin zincplate coiled on the drum shown, this plate beingcoated with a protective varnish which is scratchedoff by the point. The oscillations of the arm whichactuates the marking point also imparts, by meansof the ratchet and gear shown, a rotary and also aslow longitudinal movement to the drum carryingthe zinc plate. Another marking point, s, actuatedby a rod leading to the footplate, serves to mark byhand on the zinc plate tbe time of passing each kilo-meter post. After th
. Railway master mechanic . ing on a horizontal bar, this carrier being providedwith a marking point which bears upon a thin zincplate coiled on the drum shown, this plate beingcoated with a protective varnish which is scratchedoff by the point. The oscillations of the arm whichactuates the marking point also imparts, by meansof the ratchet and gear shown, a rotary and also aslow longitudinal movement to the drum carryingthe zinc plate. Another marking point, s, actuatedby a rod leading to the footplate, serves to mark byhand on the zinc plate tbe time of passing each kilo-meter post. After their removal from the drum thezinc plates are submitted to the action of acid, whenthe parts from which the protective varnish has beenscratched off are etched away and an engraved plateobtained from which a print can he
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Keywords: ., bookcentury1800, bookdecade1870, bookidr, booksubjectrailroadcars
