. A manual of the principles and practice of road-making : comprising the location, consruction, and improvement of roads (common, macadam, paved, plank, etc.) and railroads . ough which is to pass obliquely the iron bar, orarm, D, which connects the piston, C, with the carriage,of which HH is an axle. The valve which covers this slit,and which is shown in cross-section at B, is essentially a 336 RAIL-ROADS. Strip of leather, one edge of which is fastened to one sideof the sht, so that the rest of it can rise and fall, and thusalternately open and close the slit. In the figure it isrepresented
. A manual of the principles and practice of road-making : comprising the location, consruction, and improvement of roads (common, macadam, paved, plank, etc.) and railroads . ough which is to pass obliquely the iron bar, orarm, D, which connects the piston, C, with the carriage,of which HH is an axle. The valve which covers this slit,and which is shown in cross-section at B, is essentially a 336 RAIL-ROADS. Strip of leather, one edge of which is fastened to one sideof the sht, so that the rest of it can rise and fall, and thusalternately open and close the slit. In the figure it isrepresented as open. To strengthen it, plates of iron,each eight inches long, are attached to its upper and undersides. The under ones are just wide enough to fit intothe slit; the upper ones are a little wider, to prevent thqvalve from being pressed into the pipe. On each side ofthe slit is a rib, or projection, cast with the pipe, andforming a sort of trough, at the bottom of which the valvelies when shut. This trough is filled with a mixture oftallow and bees-wax, which, after being melted and cool-ed, adheres to the edge of the valve and makes it perfectlyair-tight. Fig. Fig. 145 is a longitudinal section of the pipe, piston,and leading carriage. The same letters of reference areemployed as in Fig. 144. A steam engine, at the end of a length of 3 miles of thepipe, works an air-pump, which draws out a portion ofthe air from the pipe, AA. The air behind the piston,(shown at C) being no longer balanced by the air beforethe piston, presses it forward. The small wheels, EEE, ATMOSPHERIC POWER, 337 behind the piston, raise the edge of the valve in order tomake way for the connecting arm, D, which draws thecarriage (of which HHH are the axles) onwjtrd with thepiston. The small wheels, FFF, behind the arm, liftup the valve to admit the air more freely to press on theback of the piston. The piston and carriage thus pro-ceed as long as there is a greater pressure of air behindthan before
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectrailroa, bookyear1853
