646 THE POPULAR SCIENCE MONTHLY. 



opens inward, is, in the first instance, held open, and a flow of water 

 is allowed to take place through it down the pipe and chamber. The 

 valve is then released, and is instantly shut by the current of water 

 which is thus suddenly stopped, and, in consequence, delivers a blow 

 similar to that produced by the fall of a hammer on an anvil, and, just 

 as the hammer jumps back from the anvil, so does the water recoil 

 back to a small extent along the pipe. 



During this action, first, a certain portion of water is forced by 

 virtue of the blow through the inner valve D opening outward into 

 the cork vessel, and so to the delivery-pipe, and instantly afterward 

 the recoil causes a partial vacuum to form in the body of the ram and 

 permits the atmospheric pressure to open the outer valve C and re- 

 establish a rush of water as soon as the recoil has expended itself. In 

 the little ram here represented, this action, which it has taken so long 

 to describe, is repeated one hundred and forty times in a minute. The 

 practical action of the ram, as modified by Mr. Anderson, demonstrates 

 that the elasticity of cork is competent to regulate the flow of water. 

 When air is used for this purpose, the air-vessel has to be filled, and, 

 with most kinds of water, the supply has to be kept up while the ram 

 is working, because water under pressure absorbs air. For this pur- 

 pose a " sniff-valve," G, is a necessary part of all rams. It is a mi- 

 nute valve opening inward, placed just below the inner valve ; at each 

 recoil a small bubble of air is drawn in and passed into the air-vessel. 

 This "sniff -valve," is a fruitful source of trouble. Its minuteness 

 renders it liable to get stopped up by dirt ; it must not, of course, be 

 submerged, and, if too large, it seriously affects the duty performed 

 by the ram. The use of cork gets rid of all these difficulties, no sniff- 

 valve is needed, the ram will work deeply submerged, and there is no 

 fear of the cork vessel ever getting empty. 



The second novel application of cork is for storing a portion of 

 the energy of the recoil of cannon, for the purpose of expending it 

 afterward in running them out. 



The result of the explosion of gunpowder in a gun is to drive the 

 shot out in one direction, and to cause the gun to recoil with equal 

 energy the opposite way. To restrain the motion of the gun, "com- 

 pressors " of various kinds are used, and in this country, for modern 

 guns, they are generally hydraulic, that is to say the force of recoil 

 is expended in causing the gun to mount an inclined plane, and, at 

 the same time, in driving a piston into a cylinder full of water, the 

 latter being allowed to squeeze past the piston through apertures, the 

 areas of which are either fixed, or capable of being automatically 

 varied as the gun recedes ; or else the water is driven out of the cyl- 

 inder through loaded valves. As a rule, the gun is moved out again 

 into its firing position by its weight causing it to run down the in- 

 clined plane, up which it had previously" recoiled. For naval pur- 

 poses, however, this plan is inconvenient, because the gun will not run 



