2G2 



HYDRODYNAMICS. 



constant and regular pulsations, unaltered and unob- 

 served. 



WATER-ENGINES, 



including those for extinguishing fires and for irriga- 

 ting gardens, are constructed on a principle quite sim- 

 ilar to that of the water-ram. Instead, however, of 

 compressing the air, as in the ram, by the successive 

 strokes of a column of running water, it is accom- 

 plished by means of a forcing-pump, driving the water 

 into the reservoir, from which it is again expelled with 

 great power by means of the elasticity of the com- 

 pressed air. Fig. Ill represents a garden-engine. 



Fig. 171. 



Gardcu-e?ighie. 



movable on wheels, which may be used for watering 

 gardens, washing windows, or as a small fire-engine. 

 Fig-. 172 (at the head of the opposite page) is another 

 of smaller size, for the same purpose, and in a very 

 neat and compact form, the working part being within 

 the cylindrical case. 



