We will next visit a mushroom-cave of another type at some little distance from that city. It is situated near Frépillon, Méry-sur-Oise--a place which may be reached in an hour or so by the Chemin de fer du Nord, passing by Enghien, the valley of Montmorency and Pontoise, and alighting at Auvers. There are vast quarries in the neighbourhood, both for building-stone and the plaster so largely used in Paris. The materials are not quarried in the ordinary way by opening up the ground, nor by the method employed at Montrouge and elsewhere in the suburbs of Paris, but so that the interior of the earth looks like a vast gloomy cathedral. In 1867 the mushroom culture was in full force at Méry, and as many as 3000 lbs. a day were sometimes sent from thence to the Paris market; but the mushroom is a thing of peculiar taste, and these quarries are now empty--cleaned out and left to rest. After a time the great quarries seem to become tired of their occupants, or the mushrooms dislike the air; the quarries are then well cleaned out, the very soil where the beds rested being scraped away, and the place left to recruit itself for a year or two. In 1867 M. Renaudot had the extraordinary length of over twenty-one miles of mushroom-beds in one great cave at Méry; last year there were sixteen miles in a cave at Frépillon. This is a clean, lonely village, just touching on the gigantic cemetery which M. Haussmann projected. [Illustration: Fig. 21. Entrance to large subterranean quarry.] The distant view of the entrance to the quarries has much the appearance of an English chalk-pit. But there is a great rude arch cut into the rock, and into this we enter, meeting presently a waggon coming forth with a load of stones, the waggoner with lamp in hand. To the visitor who has seen the mushroom caves near Paris, where it is sometimes necessary to stoop very low to avoid knocking one’s head against the roof rocks, the surprise is great on getting a little way in. At least it is so soon as one can see; the darkness is so profound that a few candles or lamps merely make it more visible. The tunnel we traverse is nearly regularly arched, masonry being used here and there, so as to render the support secure and somewhat symmetrical, the arches being flat at the top for six feet or so, and about twenty-five feet high; sometimes five feet higher. [Illustration: Fig. 22. Plan of large subterranean quarry at Fortes Terres, Frépillon. _S_, _S_, _S_, represent the plan of the bases of the huge supporting pillars, and the dotted lines their union with the roof. _D_, _C_, shows the line of the section shown in the following cut, and _P_, place for preparing the plaster. Sept. 1868.] [Illustration: Fig. 23. Section following the line _C_, _D_, in Fig. 22.]