FOUNTAINS. 



109 



FOUNTAINS. 



in a moist peaty soil, and are injured 

 by very severe frosts. The flowers 

 appear before the leaves. 



Fountains are of two kinds : jets, 

 which rise up in a single tube of water 

 to a great height, and then fall in 

 mist or vapour ; and drooping foun- 

 tains, which are forced up through a 

 pipe, terminated by a kind of rose 

 pierced with holes, called an adjutage, 

 which makes the water assume some 

 particular shape in descending. The 

 principle on which fountains are con- 

 structed is, that if a large quantity of 

 water be contained in a cistern, or 

 other reservoir, in any elevated situa- 

 tion, and pipes be contrived from it 

 to carry the water down to the ground, 

 and along its surface, that the water 

 will always attempt to rise to its own 

 level the moment it can find a vent. 

 When the orifice is large, this incli- 

 nation is only shown in a kind of bub- 

 bling upwards, as the ascent of the 

 water is prevented by the weight of 

 the atmosphere above it : but, where 

 the orifice is small, the column of 

 water will force its way through the 

 air very nearly to the height of the large 

 body of water from which it descended. 

 The height to which a jet of water 

 will ascend, therefore, depends on the 

 height which the cistern that is to 

 supply it is above the ground from 

 which it is to ascend ; and on the size 

 of the orifice through which it is to 

 issue. Something must, however, be 

 allowed for the resistance which even 

 a slender column of water meets with 

 from the air ; and something is also 

 lost by the friction of the water on 

 the pipes it passes through, if the 

 place from which the fountain is to 

 play should be far from the supply- 

 ing cistern. The time which the 

 fountain will play depends on the 

 quantity of water which the cistern 

 contains ; and the evenness and pro- 

 portion of the ascending column of 

 water on the diameter of the conduct- 



ing pipe, which should be five times 

 the diameter of the orifice. To ex- 

 plain this, we will suppose a cistern 

 erected on a summer-house twenty 

 feet high, and that a fountain is wished 

 to play about a hundred yards from 

 it, in a right line. Then if the di- 

 ameter of the descending and con- 

 ducting pipes be two inches and a 

 half, and the diameter of the orifice 

 for the jet be half an inch, the water 

 will rise about eighteen feet high. 

 It must be observed that the water 

 will rise to a less height in proportion 

 to the distance which the fountain is 

 from the cistern, the loss by friction 

 being about a foot for every hundred 

 yards ; and also that if the pipes take 

 any bend or curvature, the loss by 

 friction becomes greater. The time 

 that the fountain will continue to 

 play may be calculated by estimating 

 the quantity of water the cistern will 

 contain, as a jet of the size above de- 

 scribed will discharge about sixty-five 

 quarts a minute. The pipes should 

 be of lead, a quarter of an inch thick ; 

 as if they are too slight they are very 

 apt to burst and leak, from the great 

 weight and pressure of the water ; and 

 they should be carried deep enough 

 into the ground to be out of the reach 

 of danger from frost. They should 

 also be so contrived as to present a 

 uniform slope towards the point from 

 which the jet is to issue ; to prevent 

 an accumulation of air, or of sediment 

 from the water in the pipes, either of 

 which will prevent the fountain from 

 playing. 



Drooping fountains do not require 

 the water to rise so high for them as 

 for jets ; and consequently the cistern 

 need not be so much elevated. The 

 beauty of fountains of this kind de- 

 pends on the adjutages, which are so 

 contrived as to throw the water in 

 many different forms. For example, 

 some are intended to represent a 

 dome, and others a convolvulus, a 



