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



on the materials employed, and the manipulation to Avhich they 

 have been subjected. The inside and outside temperature have 

 also a great influence. In quarries with a low roof the temperature 

 is always high, and vegetation is consequently more rapid. The 

 duration of the crop is from forty to sixty days, and the yield 

 rapidly diminishes towards the end of that time. In quarries 

 with high roofs, or which open on to the road, the temperature 

 is lower, the vegetation is less active, and the bed lasts longer. 

 In some high-roofed quarries the beds will bear for three or four 

 months. 



A useful contrivance for facilitating the watering of the beds 

 has lately been invented ; it consists of a portable water-cistern 



I'lcni in old Subterranean Onarrics devoted to .M uslu-ooin-ctdiure, and in the oeciipation 

 of M. Renandot- 



to be strapped to the back and fitted with a rose and tubing, so 

 that a workman may carry a larger quantity of water, and apply 

 it more regularly and gently than with the old-fashioned watering- 

 pots — while one hand is left free to carry the lamp. Ati iron 

 frame was also invented, in which the bed was first compressed 

 and shaped, the frame being then reversed and the bed placed 

 in position. This method of forming the beds was afterwards 

 abandoned, owing to its being impossible to avoid fissures between 

 the lengths. On an average 2500 yards of beds are made here every 

 month. Simple mechanical contrivances to facilitate the operation 

 would, therefore, prove of the greatest advantage to the cultivator. 

 In addition to the caves in the localities above alluded to, there 



