Nikola Tesla U.S. Patent 514,169 - Reciprocating Engine Patent Wrapper Page 6

) ( T T [ perly applied to the air cushion shown but this is evidently made under some misapprehension. See Webst er, under "Spring" Knight's Mechanical Dictionary, and any work on mechanics in which it will be found that the most perfect spring known is a body of air or gas confined in a cylinder under a piston. It is further objected that there is no point in forming a chamber around the air cushion etc. we have to reply that even though the air spring used is the most perfect available in mechanics, still the imperfect elasticity of the air is the cause of the evolution of heat which is imparted to the cylinder walls by which it is confined. It is an easy matter to bring the se walls to a red heat by this means, or even hotter if so desired, so that when steam or compressed air is passed through the chamber it takes up some of this heat and carries it back into the engine proper. As the efficiency of this or any other engine depends very largely upon the difference in the temperature between the steam or air under compression as it enters the engine and after expansion, the practical value and importance of the construction will be at once apparenta. We have redrawn claim 3 to make it more specific, The remaining claims are submitted for reconsideration, without amendment. We have examined the references with great care, but gestion of even the most remote kind find no limit To this -2 51