FOUNTAINS. 401 



water in the reservoir, but on its height above the 265 



surface from which the jet rises; and, when it is con- 

 sidered that no fountain need be allowed to act in the 

 night-time, or even in the day at certain seasons of the 

 year, the quantity of water that will require to be 

 raised to the reservoir is much less than at first sight 

 will appear necessary. The greater number of foun- 

 tains in suburban gardens are indeed only played off 

 when visitors are present; and this can be effected 

 with a very moderate-sized reservoir, and with no 

 more use of the forcing- pump than may be necessary 

 to fill up the leisure time of a house servant, or a 



gardener's labourer. Though no person will undertake to erect a fountain 

 without employing an engineer, or a plumber who possesses skill and 

 experience in this branch of hydraulics ; yet it may be useful to state a 

 few particulars, with a view of enabling the proprietor of a suburban 

 residence to judge how far a fountain may be practicable in his case ; and 

 to form some notion as to whetlier the person whom he intends employing 

 to erect it, has a competent knowledge of the subject. Wlierever a fountain 

 is forced, the jet may be made to rise nearly as high as the reservoir. If 

 the reservoir be 5 ft. 1 in. above the level of the surface from which the 

 jet-d^eau is to ascend, the jet will rise 5 ft. If the reservoir should be 10 ft, 

 4 in. high, then the jet will rise 10 ft. ; and if it be 51 ft. 9 in. high, it will 

 rise 45 ft. In order to procure^ a jet of 100 ft. in height, it is necessary 

 that the reservoir be 133 ft. 4 in. high. Now the jets will rise at this 

 rate relatively to the reservoir, whether the latter contains only one cubic 

 yard of water, or 10,000 cubic yards; all the difference being, that in the 

 former case the jet would not last longer than a minute or two, because the 

 cubic yard of water would be immediately exhausted, while in the latter it 

 would last several days. The next point which a person about to erect a 

 fountain would desire to know is, the diameter of the pipe which is to convey 

 the water from the reservoir to the jet. Now this diameter may be as large 

 or as small as the party chooses : it may be a foot in diameter, or it may be 

 only an inch ; but, whatever its diameter may be, this condition is essentially 

 necessary, viz., that the orifice from which the jet issues shall be small as 

 compared with the diameter of the supply pipe, in proportion as the jet is to 

 rise high. If the jet is to rise to a maximum of height, that is, as nearly as 

 the nature of things will admit, to the height of the reservoir, then the orifice 

 must not exceed a fourth part in diameter of the orifice of the conducting 

 pipe. If, instead of a fourth part, the orifice were made of the entire width 

 of the conducting pipe, the water would hardly rise above the surface ; and 

 this, which is very remarkable, would be the case, whether the reservoir were 

 10 ft. or 100 ft. high. Thus, when the reservoir is 10 ft. 4 in. high, the height 

 to which it is wished to have the jet to rise is 10 ft., and the diameter of the 

 pipe which conveys the water to it from the reservoir is 2\ in., then the 

 diameter of the orifice must not be larger than \ in. The following Tables 

 contain useful data on this subject. The first is taken from Switzer's Intro- 

 duction to a General System of Hydrostatics, &c., vol. ii., p. 126.; and the 

 second from the excellent article on Hydraulics in the Encyclopcedia Britan- 

 nica, seventh edition, already referred to. 



