and Spouting Fountains. 229 



escape, which opening is on its upper side ; the water will be 

 projected perpendicularly, and this jet will rise higher in pro- 

 portion as the descending current has a long fall. This is the 

 construction of all jets d'eau. The demi-souterazi, which pro- 

 duces the grand jet in the Tuilleries, derives its waters from a 

 reservoir situated upon the heights of Chaillot. 



This grand hydrostatic principle, of which we have just men- 

 tioned two important applications, is wholly independent of the 

 form of the pipe in which the water is contained. It may 

 be circular or elliptical, square or polygonal, stra>ght and of 

 great length, or having many windings and ramifications ; nor- 

 withstanding every modification of this sort, the water will 

 equally rise to tlie same height, whenever it has free coui-se to 

 obey the pressure to which it is subjected. 



Let us now recall to our recollection the manner in which the 

 rain water penetrates certain beds of the stratified series ; not 

 forgetting that it is only upon the slopes of the hills, or at their 

 summits, that these beds are exposed, on edge; that it is there 

 that they admit the water, which, therefore, always occurs in 

 somewhat elevated situations : let us reflect, moreover, that these 

 water carrying beds, after having descended along the sides 

 of the hills, which formerly broke them up when they elevated 

 them, extend themselves horizontally, or nearly so, along the 

 plains; that there they are often imprisoned, as it were, be- 

 twixt two impermeable beds of clay or hard rock, — and we 

 may then easily conceive the occurrence of subterranean waters, 

 that are naturally in the same hydrostatic conditions of which 

 the pipes of common conduits, or the souterazi, supply us 

 with artificial models ; and the sinking of a pit in the valleys, 

 through the upper strata, down through the more elevated of 

 the two impermeable beds betwixt which the water is confined, 

 will form, as it were, the second branch of a pipe, in the form of 

 the letter U, already alluded to in the commencement of this 

 section, — or, we might say, of a reversed syphon, — or, finally, 

 of a smiterazi ; and the water will rise in this pit to a heioht 

 corresponding to that which the water maintains on the side 

 of the hill where it commences to descend. From these state- 

 ments every one may understand how, in any given horizontal 

 plane, the different subterranean waters, which may be placed 



