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°.
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.
The best, or, at least, most convenient situation for the bed, would be beneath that provided for the cucumber plants (see p. 18). The front may be formed of two course of brick-on-edge, and if divisions are required, they should be formed in the same way. The bottom should be made even, and rendered dry. The material for forming the bed itself consists of short stable litter, with horse-droppings, but chiefly the latter, brought to a certain state of fermentation. The droppings and litter should be obtained daily from the stable, until enough for a bed is collected; it should, from day to day, be thrown up into a flattish heap, in a dry place, where it will ferment very slightly. As soon as enough is got together to begin to ferment, the heap must be turned over; and in these turnings, the outer and inner parts of the heap, as well as the fresh and the fermenting, must be well mixed up together; the heaps should be turned every second day, and should never be made large, or else the dung would become both too hot and too dry, either of which would spoil it. To avoid this, the heaps should be flat and shallow, with as much outside as possible; in this way the air, acting on a considerable portion of it, renders it rather dry, and checks too rapid fermentation. This preparation must be continued until the whole mass is brought to an uniform mild, dryish state of fermentation. Then the bed may be made in the following manner:--About three inches of the prepared dung is laid evenly over the bottom, and is beaten down firmly with a flat heavy wooden mallet. Another layer is then put on in the same way, and this is repeated until the bed is formed to a thickness of about six inches. The next two inches of the dung should have about a sixth part of light turfy loam reduced to mould, and sifted, mixed with it to give it body. The bed is now prepared, and is to be spawned as soon as it is seen that it does not heat violently. The heat ought not to exceed 90 degrees: if it reaches higher than this, holes must be made, a few inches apart, to let the heat pass off, and in a day or two these may be filled up again. The spawn is to be put in when the heat ranges about 75 degrees; lumps of spawn about as large as a small egg may be used; a hole should be made with the fingers about two inches deep, the spawn inserted, and the material of the bed closed about it. Probably by this time there will be no danger of overheating, and if so, the soil may be put on; if, however, there is any inclination to overheat, wait till it has passed off before putting on the soil. The soil used should be decomposed turfy loam, moderately dry, so as to bear compression without running together like paste, but damp enough to become firm, close, and even, when beaten closely. About two inches in thickness should be put on, and this is to be beaten down quite firm and close. The beds are then finished. It is as well to cover the surface with a thin layer of short hay, to prevent it becoming quite dry. Mushroom beds seldom require water; after they have been some time in bearing, the beds sometimes get dry, and in such cases, if they have a moderate soaking of _tepid_ water, and the surface is covered as before, a new crop will spring up. The covering is best removed when the beds are in bearing. It is seldom advisable to apply water when the beds are coming into bearing. Water should never be used in any other than a tepid state.