PUMPING WATERS. 



73 



Pure 

 Water 



Power 

 upply. 



FIG. 55. 



it may be led by gravity from any other pure source 

 such as a spring or 



11 i r Delivery 



artesian well. In fact, 

 every case wants its 

 own special considera- 

 tion. In many cases, 

 also, two small rams 

 will often prove more 

 efficient for a particular 

 scheme than a single 

 large one. Some rams 

 have a special arrange- 

 ment of a snifting valve 

 screwed into the ram casing immediately below 

 the check valve. It usually consists of a brass plug 

 with a very small hole drilled through its axis. 

 Every time water passes through the check valve a 

 small quantity will also pass through the small orifice 

 in the snifter valve. Now when the check valve 

 closes, the consequent reaction of the water is suffi- 

 cient to cause a slight vacuum immediately under 

 the check valve, which has the effect of drawing air 

 through the snifter valve which is carried up into 

 the air vessel on the next stroke, and will prevent 

 the air in the air vessel being exhausted by the water, 

 and consequently the working of the ram is much 

 improved, bearing in mind that the air is usually 

 compressed to about half its volume when a "head " 

 of 70 ft. is the working pressure on the delivery pipe 

 of the ram. A more modern type of ram than that 

 in fig. 51 is shown in fig. 56, which includes a 

 snifter valve. Another device found on some makes 

 is that of a cylinder containing a piston acted on by a 



