As regards the kind of soil used in earthing, it is not of nearly so much importance as is generally supposed; almost any soil will do; but those having heaps of good maiden loam laid by for gardening purposes will prefer to use a coating of that. I believe that any ordinary garden soil would do, and feel certain that it is a mistake to bestow the least trouble on procuring any particular kind of soil from a distance. The beds in the caves around Paris are covered over with a white putty-like substance, which would be sufficient to shake the nerves of any British mushroom-grower accustomed to his coatings of mellow loam. It is simply the fine rubbish from the stone breakage moistened, and smoothly and firmly pressed over the beds. We, if shown this on a bed that had failed, would assuredly attribute it to the "stuff" with which the bed was covered, though finer crops than these little beds yield it would be impossible to find. I notice this subject so that failures may be traced to their true causes, and not attributed to matters which really have but slight influence. The final covering of from one to two inches of loam or other soil should not be applied till the spawn has begun to spread through the bed, but a very thin layer of dryish loam may be placed on with advantage just after spawning has taken place, as it will serve to make the surface of a more equable temperature. It is a mistake to suppose that a deep covering is of any advantage. The final earthing should be of soil sufficiently moist or moistened to permit of its being pressed into a firm surface. However, unless it is exceptionally dry, a mere sprinkling of water will suffice.
As the materials of mushroom-beds are generally moist, and as but little evaporation can take place in the structures in which they are usually grown, water is rarely necessary, and should not be applied until the surface of bed and soil are really dry. It should then be given copiously, enough to well moisten the bed, and it should be soft water heated to a temperature of 80 degrees given with a fine rose, and steadily and patiently applied equably over the whole surface of the bed. Waterings that merely wet the surface and saturate the crevices or lower parts of the bed are of no use. If one drenching is not sufficient to moisten the bed properly, another should be given. The flat form of bed is of course much more easily watered, and is on the whole the best for beds under cover. The position of beds will have a great influence on the quantity of water they require, so that it is almost impossible to give precise directions on this head; but I can scarcely conceive a case in which it will be necessary before six or eight weeks after the formation of a bed, and I have seen fine crops gathered without a single watering having been given. In watering old beds one ounce of guano to the gallon of water will prove beneficial.
