FOUNTAINS, FISHPONDS, AND ORNAMENTAL WATERS. 



97 



the fluid poured into the funnel ; when the jar is filled, it will flow out in a 

 jet so long as liquid is poured into the funnel, the jet being proportioned in 

 height to the height and diameter of the tube. 



■221. Jets exceeding the fifteenth of an inch in size never attain the natural 

 surface-level ; fi-iction at the orifice, the diffusion of the power by the spreading 

 of sjDray, and the resisting power of the atmosphere, all tend to prevent its 

 doing so. Great jets rise higher in proportion than small, except when the 

 horizontal tube leading to the orifice of the jet is very narrow, when small 

 jets rise highest. The form of the orifice also influences tlie height of the 

 jet, as was ascertained in a series of interesting experiments made by Mv. 

 Brisson, to test the power of water. He prepared an upright vessel, A B, 

 with a narrow horizontal tube, K, on 

 one side, and a larger horizontal tube, 

 OP, on the opposite side. The first was 

 perforated with three simple orifices, — 

 M two hnes, L four lines, and K eight 

 lines, in diametei-. Turning on these 

 jets, the first rose 9 feet 11 inches, 

 vertically, the second 9 feet 7 inches, bbisson's pountaiw. 



and the last, 7 feet 10 inches. In the larger horizontal tube, P, he made 

 five small orifices ; D, with a cylindrical orifice 70 lines, which rose 9 feet 

 1 inch, vertically, and 9 feet 3 inches on an incline ; E, from a conical orifice 

 94 lines by 70, rose 9 feet 6 inches vertically, and 9 feet 8 inches on an inchne ; 

 F, G, and H rose respectively, with simple orifices of eight, four, and two 

 lines, 10 feet 6 inches, 10 feet 5 inches, and 10 feet, vertically. It thus ap- 

 pears that the smaller cylindrical tube was the least effective ; that the conical 

 orifice threw the fluid much higher, and the simple orifice, with the largest 

 opening, the highest of all. Practically, a jet will rise to within a few inches 

 of the bottom of its fountain-head. For the artificial cascade, the water- 

 service need not be higher than the point at which it flows over the ledge or 

 lips of the tazza ; the ledge should be perfectly level, in order to keep up a 

 regular flow of water : a notch or other irregularity would destroy the cascade 

 "and produce a stream. On the other hand, if it is to be forced upwards, the 

 bottom of the fountain-head must be some inches above the point to which 

 the jet is to rise, and the sui^ply-pipe should lead from the lowest part of 

 the basin, descending in a continuous and uniform line, without break or 

 bend, to increase the friction. Any such departure from the direct Une must 

 be calculated in the result ; the usual calculation being that a head six inches 

 in diameter will force a column of water up a jet one-eighth of an inch in 

 aiameter. Where iron pipes are used, the deposit of calcareous matter soon 

 stops them up ; they are useless, therefore, when less than three-inch pipes, 

 imless coated, outside and in, with John's, or some other composition for 

 preventing oxidation. 



222. When the jet is to be forced higher than the fountain-head, mechanical 

 force becomes necessary, either to pump the water to a higher level, as at the 



