_Spray Pump._ Fig. 173 exhibits a carefully designed pump made to spray trees, plants, etc. All the working parts are of brass, the valves are metal; the air chamber is made of galvanized iron or copper and has large capacity. It will hold sufficient compressed air to keep the spray going from six to ten minutes after the pumping stops. The “agitators” are placed so that they keep the liquid thoroughly stirred. The plungers can be easily removed and packed without the necessity of taking the pump to a shop. [Illustration: FIG. 173.] The pump is fastened to the bottom of the barrel by a bolt passing through the barrel and secured by a nut underneath, with packing to prevent leakage, and by an iron plate at the top covering the opening through which the pump is placed in the barrel. This pump is arranged with one, or two levers, and for one or two lines of discharge hose. The cylinders are 2-1/2 inches diameter with stroke 3 inches; its capacity per stroke is 0·13 gal. _Combined Pump and Horse Power._ The “horse power” (apparatus) with its “pole” for one horse and two poles for two horses and its wrought iron “tumbling shaft” has been so modified that a horse operates the pump, by means of a “sweep,” direct connected to the pump crank shaft. The animal will make three to four circuits per minute, giving the pump crank shaft a speed of 40 to 50 revolutions per minute. The capacity of a 4 in. plunger and 8 in. stroke is given as 3·120 gallons per hour; the suction pipe is given as 3-1/2 in. diam. and the discharge as 3 in. pipe. DRIVEN OR TUBE WELLS. [Illustration: FIG. 175.] [Illustration: FIG. 175-A.] Aside from the wells described on page 45 and those following it, there are wells made by forcing iron tubing down into the earth until a water supply is reached. Within reasonable distances and in a remarkably large proportion, these pipe wells are directly connected with the suction part of hand pumps. NOTE.—“When a well fails to yield a fair amount of oil or water, an increase in the flow is often effected by means of the Roberts torpedo. This is a thin water-tight cylinder of metal or paper, 4 to 6 ft. long and 2 or 3 in. in diameter, charged with powder, gun-cotton or nitro-glycerine. It is lowered to the bottom of the well, or to a depth that will bring it opposite the desired stratum, and the well is then flooded. The charge is exploded by a cap or electric spark, and the explosion often clears away the obstruction from the oil or water vein. This applies particularly to deep wells.” To this class also belong the famous oil and artesian wells which penetrate through earth and rock thousands of feet, many of them operated by power pumping machines. [Illustration: FIG. 176.] [Illustration: FIG. 177.]