Knowing this to be the case, it occurred to Mr. Philip Brasher that some other means of disturbing the rhythmic movement of the water might be found, and he determined to try the experiment of using compressed air for this purpose. Accordingly he laid a perforated pipe under water and connected it with an air compressor. Then when a storm arose air was pumped into the pipe and it rose in bubbles through the water. The effect of this upward movement of air was instantly observable. It upset the rhythmic water currents and the waves which struck this wall of air bubbles curled and broke as if they had encountered a shoal of sand. Several exposed piers on the Pacific coast have had a pneumatic breakwater built around them so as to protect them or ships lying alongside from being pounded by the waves. There is no expense attached to the breakwater except in time of storm when the air pumps must be kept going. One important advantage of the breakwater is that it does not block navigation. A ship can sail right over the wall of bubbles and find refuge behind it. CHAPTER VIII AIR SPRINGS AND CUSHIONS UNLIKE water, air is a highly compressible, elastic fluid, and as such furnishes an excellent medium for the storage of energy. It acts just like a clock spring into which energy may be introduced and stored by winding or compressing the spring. The energy remains locked up in the spring and when the spring is released, it gives back just as much energy as was put into it, except for slight frictional and heat losses. Air is a much better spring than steel or any other metal because it never loses its elasticity from fatigue and because it has an enormous capacity for the storage of energy. It possesses one serious drawback, however. Much of the energy that is expended in compressing it is converted into heat. If the air were to be used immediately and without transmitting it to a distance, there would be no advantage in extracting the heat, but heat cannot be stored in air for long and it would gradually escape from the storage reservoir or air receiver and from the pipes leading the air to the machines that it was to operate. As the heat escaped it would lower the pressure of the air and hence much of the energy would be lost. HEAT OF COMPRESSION In Chapter V we described a hydraulic system of compressing air and noted that one of the advantages of this system is that it delivers air cooled to the temperature of the water. This, of course, does not mean that there is no loss due to heat. The air bubbles as they are compressed are cooled by the water that compresses them; in other words, the heat of compression passes off into the water, making the water warmer than it would otherwise be. Heat is not produced without expenditure of energy and a certain proportion of the water power is thus wasted.