a few minutes, and causes the fulminating powder to adhere; the caps are now complete. The old form of caps was a simple short cylinder, but it is found better to allow the four little flaps to remain on, that the right end may be distinguished and instantly placed on the nipple the proper side downwards, which cannot otherwise so readily be done in the dark, and when the hands are benumbed with cold. PUMPS AND FIRE ENGINES. Illustration: FIG. 1. (‡ COMMON LIFTING PUMP.) Pumps are used for lifting fluids above their level into some higher situation, such as from the hold of a ship or from a well. Fig. 1 shows the different parts of a common “lifting pump;” _a a_ is a cylinder, _b_ a piston rod or “plunge,” _c_ the sucker made of leather to fit nicely the cylinder, _d_ a valve in the sucker to open upwards, _e_ a valve fixed to the cylinder, also to open upwards, _f_ a box with a spout. Illustration: FIG. 2. (‡ AIR PUMP.) The piston being raised by lowering the handle of the pump, a partial vacuum is formed below the upper valve, which shuts down directly the piston is raised by the pressure of the air; this vacuum causes the external air to force the water some way up the tube _g_. On the piston descending, the lower valve is forced down and the upper one opened, this keeps the water where it is and allows the piston to descend without forcing the water down again, and on its being raised a second time the upper valve shuts and the lower one opens, the water being drawn up still higher, and this takes place till the box at the top is full to the spout, when it runs out. The air-pump is on the same principle, and is generally made with two cylinders worked by means of a “rack” and wheel (fig. 2); this is only to save time, instead of pumping water it pumps out air from any vessel called a “receiver,” because it receives any object to be placed in a “vacuum,” that is to say a partial vacuum, for the air-pump cannot produce a vacuum, as the air is only partly removed by each stroke of the piston, leaving the air more rarefied inside; and although each stroke of the piston increases the rarefaction, yet it cannot get all, as it merely takes part, and always leaves part. Illustration: (‡ FIRE ENGINE.) Illustration: FIG. 3. (‡ AIR CHAMBER.)