3Q8 ON SIPHONS AND JETS OF WATER. 



of the water. We may obtain a sufficiently accurate determination 

 of the velocity, by supposing the height of the reservoir above the 

 orifice of the pipe to be diminished in the same proportion as the 

 diameter of the pipe would be increased by adding to it one-fiftieth 

 part of the length, and finding the whole velocity corresponding 

 to four-fifths of this height. Thus, if the diameter of the pipe 

 were one inch, and its length 100 inches, we must suppose the 

 effective height to be reduced to one third by the friction, and the 

 discharge must be calculated from a height four-fifths as great as 

 this, which may be considered as a recluc ion derived from the in- 

 terference of the particles, entering the pipe, with each other's mo. 

 tions. If the diameter of the pipe had been two inches, the height 

 must only have been supposed to be reduced to one-half bv the 

 friction ; such a pipe would, therefore, discharge about five times 

 as much water as the former, although of only twice the diameter ; 

 and this circumstance requires the attention of all those who are 

 concerned in regulating the distribution of water by pipes fur do- 

 inestic use, or for any ether purpose. 



In such cases it becomes also frequently necessary to attend to 

 the angle in which a small pipe is inserted into a larger; whenever a 

 pipe is bent, there is a loss of force according to the degree of flex- 

 ure, and to the velocity of the water, which may be calculated, if it 

 be required ; but if a pipe be fixed into another through which the 

 water is moving very rapidly, in a direction contrary to that of the 

 stream, its discharge will not only be much smaller than if the di, 

 rections more nearly coincided, but sometimes such a pipe will dis- 

 charge nothing at all; on the contrary, like the air in Hauksbee's 

 experiment, the water which it contains may be dragged after the 

 stream in the larger pipe. 



[l~oung's Nat. Phil} 



SECTION IV. 



On Siphons and Jets of Water. 



IT is very well known that the general weight and pressure of the 

 atmosphere upon liquids is capable of throwing them up into tubes 

 of a considerable height, one of whose extremities is immersed in 

 the reservoir of the liquid made use of for this purpose, and the 

 other constituting an exhausted receiver or vacuum. Liquids, how- 



