When twin-screws are used, one screw is righthanded and the other left-handed, so that, being turned in contrary directions in driving ahead, they may counteract each other's tendencies to produce lateral vibration.
Griffith's had a hollow spherical ball, forming an enlargement of the hub, being substituted for the central portion of the blades.
The blades taper toward the extremities.
The pitch is alterable, by the rotation of each screw on its stem, which is rof cinder and metal have been again charged, and the process is continued.
From eight to ten charges are made before any refettling is required, and these heats are worked in a day of ten hours. See puddling-furnace.
BeadlestoneDec. 9, 1857
HeatonAug. 13, 1867
of a locomotive railway-engine employed in the vicinity of Merthyr Tydvil in 1804; of mining-engines and machinery and coining apparatus for the silver regions of Peru; of ore-refining furnaces; and of various improvements in steam-engines, hydraulic engines, propelling and towing vessels, discharging and stowing ships' cargoes, floating-docks, construction of docks, buoys, steam-boilers, heating apartments, etc.
Trevethick's steam-carriage (longitudinal section).
Griffith's steam-carriage, patented 1821.
The engine part of the carriage was supported on two driving-wheels.
The boiler consisted of tiers of water-tubes arranged in the fire-box.
The upper row of tubes, being filled with steam and exposed to the furnace heat, may be compared to some of the modern superheaters.
The connection from the piston to the driving-axle was by sweep-rods, the lower ends of which were provided with driving pinions and detents operating upon toothed gear attached to the