316 Cooper'' s Rotative Piston. 



To protect life and property against fire has ever been an 

 object of great importance, and the ingenuity of man has 

 from time to time invented and adopted a variety of means 

 to enable him to resist with success the inroads of this dan- 

 gerous element. To the individual, safety is found in some 

 degree by insurance, but the root of the evil is still untouched, 

 and nothing short of actual care and exertion can be sure 

 of operating as a perfect safeguard. Experience has long 

 since shown, that the simple power of man, without the aid 

 of mechanical ingenuity, is not sufficient to arrest the pro- 

 gress of fire, after it has once overstepped its proper bounds. 

 It becomes then an object of vital interest, that that ingenu- 

 ity should be so directed as to secure the object in the best, 

 while prudence dictates it should be done in the most eco- 

 nomical, manner. It would be wasting time, to go into a 

 minute examination of the machines which have been, from 

 time to time, invented for the purpose of discharging water 

 upon fire, and useless to point out the advantages or defects 

 of every invention which humun ingenuity has placed in the 

 possession of the public : suffice it for us to point to those 

 which are now in use. Even here the variety will preclude 

 a minute description of each, and we will only state what is 

 known to all, that they are generally made with one or more 

 piston cylinders, placed either perpendicularly or horizontally, 

 with solid or valve pistons playing in them, with a recipro- 

 cating motion. In this way one object is accomplished, viz. 

 the discharging of water to a much greater distance, than it 

 can be thrown with simple power. But with this advantage 

 there is a disadvantage, in as much as the stream being ope- 

 rated upon directly by the power, gives, in its motion, an ex- 

 act representation of the mode of its application ; conse- 

 quently the stream is as unequal as the force applied, and, at 

 every change of the piston, stops. To remedy this defect, 

 a vessel filled with air is placed in the vicinity of the piston 

 cylinder, and the water, ere its final discharge, is forced into 

 the bottom of this vessel and then allowed to escape. As 

 the pipe, through v^/hich the water makes its final escape, is 

 generally much smaller than the piston cylinder, consequent- 

 ly the motion of the piston will produce compression on the 

 water at every stroke, while the air, in the air chamber, be- 

 comes compressed in like manner. The advantage, then, 

 of the air chamber is, that this compressed air operates upon 

 the water as a spring, and exerts its power during the suspen- 



