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The systematic measurement of rainfall is one of those pursuits which prove more interesting in the doing than in the prospect. It enables us to compare one season or one year with another; tells us what the weather has been while we slept; affords a little mild excitement when thunderstorms are about; and compensates to a limited extent for the disadvantages of a wet day. The general practice is to examine the gauge daily (say at 10 a.m.); to measure the water, if any, collected during the previous twenty-four hours; and to enter the record at once. Gauges are made which record automatically the rainfall on a chart or dial, but these are necessarily much more expensive than those which merely catch the water for measurement. This last class, to which our attention will be confined chiefly, all include two principal parts—a metal receiver and a graduated glass measure, of much smaller diameter than the receiver, so that the divisions representing hundredths of an inch may be far enough apart to be distinguishable. It is evident that the smaller the area of the measure is, relatively to that of the receiver, the more widely spaced will the graduation marks of the measure be, and the more exact the readings obtained. [Illustration: FIG. 151.—Standard rain-gauge.] The gauge most commonly used is that shown in Fig. 151. It consists of an upper cylindrical part, usually 5 or 8 inches in diameter, at the inside of the rim, with its bottom closed by a funnel. The lower cylindrical part holds a glass catcher into which the funnel delivers the water for storage until the time when it will be measured in a graduated glass. The upper part makes a good fit with the lower, in order to reduce evaporation to a minimum. Such a gauge can be bought for half a guinea or so, but one which, if carefully made, will prove approximately accurate, can be constructed at very small expense. One needs, in the first place, a cylindrical tin, or, better still, a piece of brass tubing, about 5 inches high and not less than 3 inches in diameter. (Experiments have proved that the larger the area of the receiver the more accurate are the results.) The second requisite is a piece of stout glass tubing having an internal diameter not more than one-quarter that of the receiver This is to serve as measuring glass.