This consists of a wide glass tube, _a_, into which another tube, _b_, _b′_, _b′′_, passes air-tight. _c_ is an india-rubber tube connecting a with the water supply, _d_ is a clamp to stop the flow of water through _c_. _e_ is another clamp to regulate the flow, _f_ is a reservoir to prevent any water which may accidentally come over from getting into _j_. _g_ is a plug to let out any water from _f_. _h_ is a screw for connecting a air-tight to a piece of tubing, which should pass 32 feet, if possible, below the level of _a_. _i_ is a piece of strong india-rubber tubing to connect the pump with the vessel to be exhausted. The water rushes in at _c_ and down _h_, carrying bubbles of air with it till the exhaustion is complete. The figure illustrates a common application of this pump to the rapid filtration of liquids which ordinarily pass through paper with difficulty. _a_ is represented as being about half full of water. _k_ is a funnel fixed air-tight in the india-rubber stopper of the bell-jar _j_. _l_ is a small cone of platinum foil to prevent the paper filter which fits into it from being broken. _m_ is a plate of ground glass, _n_ is a beaker to receive the filtrate. [Illustration: Bunsen’s water-air-pump.] =Air-pump, Sprengel’s.= This apparatus depends on the principle of converting the space to be exhausted into a torricellian vacuum. In the subjoined figure, _c_, _d_ is a glass tube longer than a barometer, open at both ends, and connected by means of india-rubber tubing with a funnel, A, filled with mercury and supported by a stand. Mercury is allowed to fall in this tube at a rate regulated by a clamp at C; the lower end of the tube, _c_, _d_, fits in the flask B, which has a spout at the side a little higher than the lower end of _c_, _d_; the upper part has a branch at _x_ to which a receiver R can be tightly fixed. When the clamp at C is opened, the first portions of mercury which run out close the tube and prevent air from entering below. As the mercury is allowed to run down the exhaustion begins, and the whole length of the tube from _x_ to _d_ is fitted with cylinders of air and mercury, having a downward motion. Air and mercury escape through the spout of the bulb B, which is above the basin H, where the mercury is collected. It is poured back from time to time into the funnel A, to be repassed through the tube until the exhaustion is complete. [Illustration: Sprengel’s air-pump.] =AIRY’S (Dr.) NATURE’S MEDICAL TREATMENT= is the title of a pamphlet which recommends four secret remedies against 166 diseases: _a._ The Pain Expeller, a mixture of about 35 parts of tincture of capsicum, 20 parts of diluted spirit, and 20 parts of spirit of ammonia. _b._ Sarsaparillian, a fluid extract of sarsaparilla and China root, containing 1 per cent. of iodide of potassium.