STEAM PUMP. The simplest steam pump is the siphon pump, which acts upon the principle of the tromp (q.v.), except that the motion of steam causes the motion of the water, while in the tromp the motion of the water propels the air. A tube through which the steam is forced enters a hollow globe to a little beyond its center. On either side of this tube are openings into the globe for the entrance of water. These openings are much larger than the steam pipe. Opposite the latter is the exit tube for the mixed steam and water, having a trumpet shape and a length of about once and a half times the diameter of the globe. The rush of steam' across the semi-diameter of the globe and through this funnel produces exhaustion in the intend halves of the globe, ,into which spaces the water is forced by the external pressure oh the air. The first direct acting piston pumps were probably invented by Mr. II. II. Worthington of New York. while making experiments for canal steam navigation iu 1840. He patented a steam pump for feeding marine boilers in 1844. The steam cylinder was fed through a pipe which had a valve at the other end within the boiler. To this valve there was adjusted a float which controlled the supply of steam, which extended the cylinder through a slide valve which was acted upon by a spring controlled by the motion of the piston. The present Worth ington and Baker pump was evolved from this apparatus. It is a combination of pump and steam cylinder, driven by direct action and without intervention of fly-wheel or any appliance for producing rotary motion. The steam cylinder has the usual arrangement for the entrance and exit of steam, and the rod and piston is attached to a plunger of a double acting pump. At the middle of the piston rod, between the pump and steam cylinder, there is attached an arm which iu passing to and fro strikes the lung end of a lever, which changes the steam valves so as to alternately admit steam on one side or the other of the piston. Various improvements have been made to control the action of the slide valve. One method is the employment of a secondary cylinder and piston, to which
steam is admitted by a sub-valve, acted upon by the main piston, near the end of the stroke. Another method is the employment of a liy-wheel. We will first mention those pumps having an attached crank and 'fly-wheel. Of these an example is furnished by the Eclipse steam pump, made at Pittsburg, Penn. The crank-shaft actuates a rocking lever, which moves the slide controlling the admission and exhaust of steam. The Clay ton pump, made at Brooklyn, N. Y., has a yoke which couples the piston and pumping rods, and answers for the support of the crank-shaft journal. One end of the shaft, by suitable attachments, controls the valve, while the other supports the fly-wheel. These fly-wheel pumps have the advantage of a perfect control of the steam valve. The direct acting pumps have been the su'ject of many inventions, the principal object sought being the arrest of the piston at any rate of speed at a proper distance from the cylinder head. This has been accomplished by various devices. We have not space to describe the dif ferent forms of apparatus, hut will mention the following as good examples:—Knowles's steam pump, which employs an auxiliary piston-valve. or chest-piston, which has a recip rocating and rotary motion, which imparts motion to the main valve; Blake's steam pump, in which both the main and the auxiliary valves are plain, flat slide-valves, the auxil iary valve being a continuation of the ports of the main cylinder, and therefore forming a movable valve-seat; the Cameron steam pump, in which the steam-piston, at the end of the stroke, acts 'upon valves at either end of the cylinder, alternately admitting and exhausting steam; the isochromal steam pump, made at Hamilton, Ohio, which has a governor to regulate the strokes of the piston; and the National steam pump, in which the valve-gear consists of a main piston-valve, doing the work of an auxiliary piston, the valve stein performing the office of an auxiliary valve.