Burying a ripe specimen in similar soil, and watering ground with the spores, has been tried without success.[A] As to the methods adopted for cultivation of the common mushroom, it is unnecessary to detail them here, as there are several special treatises devoted to the subject, in which the particulars are more fully given than the limits of this chapter will permit.[B] Recently, M. Chevreul exhibited at the French Academy some splendid mushrooms, said to have been produced by the following method: he first develops the mushrooms by sowing spores on a pane of glass, covered with wet sand; then he selects the most vigorous individuals from among them, and sows, or plants their mycelium in a cellar in a damp soil, consisting of gardener's mould, covered with a layer of sand and gravel two inches thick, and another layer of rubbish from demolitions, about an inch deep. The bed is watered with a diluted solution of nitrate of potash, and in about six days the mushrooms grow to an enormous size.[C] The cultivation of mushrooms for the market, even in this country, is so profitable, that curious revelations sometimes crop up, as at a recent trial at the Sheriffs' Court for compensation by the Metropolitan Railway Company for premises and business of a nurseryman at Kensington. The Railway had taken possession of a mushroom-ground, and the claim for compensation was £716. It was stated in evidence that the profits on mushrooms amounted to 100 or 150 per cent. One witness said if £50 were expended, in twelve months, or perhaps in six months, the sum realized would be £200. Immense quantities of mushrooms are produced in Paris, as is well known, in caves, and interesting accounts have been written of visits to these subterranean mushroom-vaults of the gay city. In one of these caves, at Montrouge, the proprietor gathers largely every day, occasionally sending more than 400 pounds weight per day to market, the average being about 300 pounds. There are six or seven miles' run of mushroom-beds in this cave, and the owner is only one of a large class who devote themselves to the culture of mushrooms. Large quantities of preserved mushrooms are exported, one house sending to England not less than 14,000 boxes in a year. Another cave near Frépillon was in full force in 1867, sending as many as 3,000 pounds of mushrooms to the Parisian markets daily. In 1867, M. Renaudot had over twenty-one miles of mushroom-beds in one great cave at Méry, and in 1869 there were sixteen miles of beds in a cave at Frépillon. The temperature of these caves is so equal that the cultivation of the mushroom is possible at all seasons of the year, but the best crops are gathered in the winter.