508 THE PARKS AND GARDENS OF PARIS. [Chap. XXX. 



with two or three lines of heds, daylight is again seen, this time 

 coming through another well-like shaft, formerly used for getting 

 up the stone, but now for throwing down the materials for the 

 Mushroom-beds. At the bottom lies a large heap of the white 

 earth before alluded to, and a barrel of water — for gentle waterings 

 are required in the cool, black stillness of these caves. 



We find but little unpleasant smell, for the galleries are all 

 thoroughly ventilated, not only for the sake of the labourers, but 

 of the Mushrooms, which would not thrive in confined air. If 

 the air were not frequently changed, the workmen, the lamps, 

 and the gases given off by the slow fermentation of the material 

 would soon render the quarries unfit for the culture. The 

 ventilation is accomplished by means of small shafts here and 

 there, surmounted by wooden chimneys, with the upper end cut 

 at an angle. The top of the chimneys is above the level of the 

 mouth of the principal shaft, and the bevelled edge turned towards 

 the north. The number of ventilating-shafts and their distances 

 apart must be regulated by the special wants of each mine. Fre - 

 quently the Mushroom-growers content themselves with using the 

 ventilating-shafts constructed by the former owners of the pit, 

 seeing that the construction of each shaft costs from £8 to £40, 

 according to its depth. It sometimes happens that two quarries 

 communicate, in which case the ventilation is an easy matter ; it 

 is, however, necessary to guard against strong draughts and 

 sudden changes of temperature, which would interfere with the 

 well-being of both the men and the Mushrooms. For this 

 purpose the usual means employed for the ventilation of coal- 

 mines, such as fires and trapdoors, is adopted. When the entrance 

 to the quarry is by a horizontal gallery, as at Mery, level with 

 the road, the ventilation is comparatively simple, and the work of 

 cultivation much easier. The caves are let at from £6 to £16 per 

 month, according to the extent and height of their galleries, and 

 the facilities for ventilating them. Atmospheric variations, both 

 inside and out, must be narrowly watched, so that the temperature 

 of the quarry may not rise or fall too far above or below the 

 average, and that the ventilating-currents may always be kept in 

 the same direction and of the same strength. If the beds are in 

 a cavern, the draughts should be in the direction from north to 

 south, and the ventilating-shafts and their dampers should be so 



