Mr. Belville, of the Royal Observatory, has constructed the following Table, from a series of observations made with Simmons' hygrometer in connexion with the dew point, as obtained by a Mason's hygrometer, or a dry and wet thermometer. +------------------------------------------------------------------+ | Range Mean | | |of Simmons' Humidity of| | |Hygrometer. the Air.| | +--------------------------| | | 20° to 30° 1·00 |Extreme saturation; air precipitates | | | moisture at a fall of temperature. | | 30 .. 40 0·96 | | | 40 .. 50 0·89 | | | 50 .. 60 0·81 | | | 60 .. 70 0·77 | } | | 70 .. 80 0·72 | }Ordinary fine dry weather. | | 80 .. 90 0·67 | } | | 90 .. 100 0·59 | | |100 .. 120 0·50 | Air contains one half of the moisture | | | it is capable of holding in solution;| | | in England very dry weather. | +--------------------------+---------------------------------------+ Example:--Suppose hygrometer read 45°, the mean humidity corresponding is 93. Again, if hygrometer read 90°, the mean humidity corresponding is 59°. _Mushrooms._ (See p. 22.) Convenience for growing mushrooms may always be planned in a cucumber house; and as these excellent fungi are universally approved, it may be useful to append an epitome of the mode in which they should be cultivated.