will remain so, in spite of any gale of wind or ordinary circumstances. Its correctness in this respect should be tested from time to time.
4. Height. The funnel of gauges newly placed should be one foot above grass. Information respecting height above sea level may be obtained from G. J. Symons, Esq., 64, Camden Square, N.W., London.
5. Rust. If the funnel of a japanned gauge become so oxidised as to retain the rain in its pores, or threatens to become rusty, it should have a coat of gas tar or japan black, or a fresh funnel of zinc or copper should be provided.
6. Float Gauges. If the measuring rod is detached from the float it should never be left in the gauge; if it is attached to the float it should be pegged or tied down, and only allowed to rise to its proper position at the time of reading. To allow for the weight of the float and rod these gauges are generally so constructed as to show 0 only when a small amount of water is left in them. Care must always be taken to set the rod to the zero or 0.
7. Can and Bottle Gauges. The measuring glass should always be held upright. The reading is to be taken midway between the two apparent surfaces of the water.
8. Date of Entry. The amount measured at 9 a.m. on any day is to be set against the previous one, because the amount measured at 9 a.m. of, say, the 17th, contains the fall during fifteen hours of the 16th, and only nine hours of the 17th. (The rule has been approved by the meteorological societies of England and Scotland, cannot be altered, and is particularly commended to the notice of observers.)
9. Mode of Entry. If less than one tenth (·10) has fallen, the cipher must always be prefixed; thus, if the measure is full up to the seventh line, it must be entered as ·07—that is, no inches, no tenths, and seven hundredths. For the sake of clearness it has been found necessary to lay down an invariable rule that there shall always be two figures to the right of the decimal point. If there be only one figure, as in the case of one tenth of an inch (usually written ·1), a cipher must be added, making it ·10. Neglect of this rule causes much inconvenience. All columns should be cast twice—once up and once down—so as to avoid the same error being made twice. When there is no rain a line should be drawn rather than a cipher inserted.
10. Caution. The amount should always be written down before the water is thrown away.
11. Small Quantities. The unit of measurement being ·01, observers whose gauges are sufficiently delicate to show less than that are, if the amount is under ·005, to throw it away; if it is ·005 to ·010 inclusive, they are not to enter it as ·01.
12. Absence. Every observer should train some one as an assistant; but where this is not possible, instructions should be given that the gauge should be emptied at 9 a.m. on the 1st of the month, and the water bottled, labelled, and tightly corked, to await the observer’s return.