1853. Johnston's portable garden engine (fig. 475.) is a very useful instrument. On raising the handle a, the water passes up the lower tube, opening the valve b, and filling the tube c. Depressing the handle closes the valve b, and opens the valve d; the water passing up the tubes e and f, and compressing the air in the outer tube f, when it continues up the tube e to the joint g, through which it passes out at the jet, with or without the rose h; the joint being movable up or down. On the handle being raised again, the valve d closes, and the valve b opens for the water to fill the tube c. At the same time that the tube c is filling, the air compressed in the tube f is expanding, and forcing the remaining water in the tubes e and f to flow out of the jet. This process being repeated at each stroke of the pump, causes a perpetual stream, which may be thrown out sixty feet. The conducting tube k screws off at i, rendering the instrument extremely portable.