STATIONARY ENGINES.

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handles or horns keyed to each shaft. The tappet or sliding bar forthe steam valve is a long wrought-iron bar, quite parallel in itsentire length, secured to the plug rod with eyes at the ends, andset screws passing through these eyes, the point of the screw press-ing against the plug rod. This is necessary, as the steam may be cutoff quickly, or say at one-fourth of the stroke of the piston, conse-quently the bar would require to be somewhat more than three-fourths of the stroke of the plug rod, so as to keep the steam valveshut. The two other tappets are round arms, secured to the plugrod in the same way, having a series of leather washers screwed upagainst a collar, with a nut and metal washer at the end of theprojecting bar. On the steam and exhaust shafts a catch and paulare fitted for each, keeping the valves shut until released by thecataract, which consists of a pump worked by the down stroke ofthe plug rod, with a weighted lever so arranged that the oil or wateris forced out of the pump, the delivery being regulated by a valveor plug tap. On the end of the weighted lever there is a rodpassing upwards for raising the pauls, which can be adjusted atpleasure; thus the catches are freed, and the weight arm lifts thevalve. A quadrant is keyed on the middle and bottom shaft tokeep the equilibrium valve shut. When the exhaust valve is openthe top quadrant abuts on the lower one, and keeps the equilibriumvalve shut until it is released, when the tappet for the bottom shutsoff the exhaust, and allows the quadrant to pass the equilibriumquadrant, thus releasing it, and the valve is instantly opened bythe weight arm.

Now we will suppose the piston at the top of the cylinder, andthe exhaust valve full open by the cataract releasing the bottomcatch; the cataract rod, still moving upwards, releases the top catch,and the steam valve is instantly raised by the weight-arm, the pistonat once descends, until the long parallel tappet cuts off the steam; theplug rod still moves on until one of the tappets shuts the exhaust atthe end of the piston stroke, and as the equilibrium valve was heldin position by its quadrant, at the moment the exhaust is shut theequilibrium valve opens; so the steam is thus allowed to escapefrom the top of the piston to the under side of it, the descent of thepump rods placed at the other end of the engine beam being regu-lated by the amount of opening of the equilibrium valve, which canbe further regulated by the throttle valve at pleasure wire-drawingthe steam in the passages from the top to the under side of the