THE SYPHON. 



LESSON 25. 



Jli/draulics. 



Intermittent, coming by fits, not constant. 

 Res'ervoir, a conservatoiy of" water ; a store. 

 VaCuum, a space unoccupied by mattef. 



The science of Hydraulics teaches how to estimate the 

 Velocity and force of fluids in motion. Upon the principle 

 of this science all machines worked by water are constructed, 

 as engines, mills, pumps, and others. Water can be set in 

 motion by its own gravity, as when it is allowed to descend 

 from a higher to a lower level ; and by an increased pressure 

 of the air, or by removing the pressure of the atmosphere, 

 it will rise above its natural level. In the former case it 

 will seek the lowest situation, and in the latter, it may be 

 forced to almost any height. 



The syplwii is a pipe used to draw off water, wine, or other 

 fluids, from vessels which it would be inconvenient to move 

 from the place in which they stand. It is made of tin or 

 copper, and bent in such a manner that one limb may reach 

 down through the hole in the top of the vessel to be emptied, 

 to its very bottom ; the other limb should be the longest, so 

 that when filled it may contain a heavier body of fluid than 

 tliat within the vessel. The pressure of the atmosphere being 

 taken off from that part of the surface of the liquor within 

 the tube, the liquor rises above its natural level, and flows 

 through the longer liuib, and the contents of the vessel are 

 drawn off to the last. There are intermittent springs in va- 

 rious places of the woi'Id, which have been explained on the 

 principle of the syphon. A passage for the water may have 

 been formed in the soil, and when the internal cavity has 

 been filled witli water, so as to begin to run off by this passage, 

 the pressure of the atmosphere will make the water flow till 

 all is carried off. Of course the spring then ceases until the 

 cavity is again filled with water, when the same phenomenon 

 is repeated. Fluids may be conveyed over hills and valleys 

 in bent pipes, to any height which is not greater than the 

 level of the spring whence they flow. The Romans, either 

 from their ignorance of the pressure of fluids, or from their 

 love of magnificence, conveyed water across valleys by 



