BOOK III. CONVENIENT DECORATIONS. 359 



strosity, relatively to the surrounding scenery, or to that whole of which it should form an 

 accordant part. 



1829. Jets and other hydraulic devices, though now less in repute than formerly, are not 

 to be rejected in confined artificial scenes, and form an essential decoration where the 

 ancient style of -landscape is introduced in any degree of perfection. 



1830. The Jtrst requisite for jets or jn-ojected sjjouts, or threads of water, by atmospheric 

 pressure, is a sufficiently elevated source or reservoir of supply. This being obtained, 

 pipes are to be conducted from it to the situations for the jets. No jets, however con- 

 structed, will rise as high as the fountain-head ; because the water is impeded by the re- 

 sistance of the air, the friction against the opening of the pipe or adjutage, and its own 

 gravity. It is not easy to lay down data on this head ; if the bore of the adjutage be too 

 small, the rising stream will want sufficient weight and power to divide the air, and so being 

 clashed against it will fall down in vapor or mist. If too large, it will not rise at all. The 

 length of pipe between the reservoir and the jet will also impede its rising in a slight degree 

 by the friction of the water on the pipe. This is estimated by P. J. Francois (Art des 

 Fontaines, 1 37. ) at one foot for every hundred yards from the reservoir. The proportion 

 which this author gives to the adjutages relatively to the conducting-pipes, is one fourth ; 

 and thus for a jet of four lines, or a third of an inch, he requires an adjutage of between 

 four and five lines, and a conducting pipe of one inch and a half diameter ; for a jet of six 

 or seven lines, a conducting-pipe of two inches, and so on. From these data, the height 

 of the fountain and the diameter of the conducting-pipe being given, the height to which 

 a jet can be forced can be estimated with tolerable accuracy, and the contrary. But where 

 the pipes are already laid, and the power of the head, owing to intervening obstructions, 

 not very accurately known, the method by trial and correction by means of a leaden nozzle, 

 the orifice of which inay be readily increased or diminished, will lead to the exact power 

 under all the circumstances. 



1831. Adjutages are of various sorts. . Some are contrived so as to throw up the water 

 in the form of sheaves, fans, showers, to support balls, &c. ; others to throw it out hori- 

 zontally, or in curved lines, according to the taste of the designer ; but the most usual 

 form is a simple opening to throw the spout or jet upright. The grandest jet of any is 

 a perpendicular column issuing from a rocky base, on which the water falling, produces 

 a double effect both of sound and visual display. A jet rising from a naked tube in 

 the middle of a basin or canal, and the waters falling on its smooth surface, is unnatural, 

 without -being artificially grand. 



1832. Drooping fountains (^gs. 341, 342, 343.), overflowing vases, shells (as the 

 chama gigas), cisterns, sarcophagi, dripping rocks, and rockworks, are easily formed, 

 requiring only the reservoir to be as high as the orifice whence the dip or descent pro- 

 ceeds. This description of fountains, with a surrounding basin, are peculiarly adapted 

 for the growth of aquatic plants. Both classes of water-works successfully combine. 



341 342 



1833. Vfaste-drains. In all water-works in gardens, pipes or drains must be contrived 

 to carry off such of the water as is not used in culture. The diameter of these should be 

 somewhat larger than the conducting-pipes, for obvious reasons. 



1834. Sun-dials are venerable and pleasing garden-decorations ; and should be placed 

 in conspicuous frequented parts, as in the intersection of principal walks, where the 

 " note which they give of time" may be readily recognised by the passenger. Elegant 

 and cheap forms are now to be procured in cast-iron, which, it is to be hoped, will render 

 their use more frequent. 



1835. Vanes are useful in the same way, but are an unsuitable garden-ornament, 

 though frequently introduced on the summits of garden-buildings. The ideas to which 

 they give rise, as connected with ships, flags, fairs, military standards, &c. are all oppo- 

 site to the stillness and repose of gardens. Over a library or office they are useful, con- 

 nected with an internal index ; and they are characteristic and proper over churches, 

 family-chapels, clock-towers, and domestic offices. 



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