SfA WILLIAM SIEMENS, I'.R.S. 47 



the attainment of some more perfect result than could hitherto be 

 obtained. The author will therefore attempt to state his views of 

 the characteristics of a perfect engine. 



1st. All the elastic material employed should actually enter the 

 working cylinder (or its substitute), and produce its full value of 

 effective displacement of piston, without deduction for the 

 resisting pressure, or the working of pumps. 



2nd. The production of the elastic material, previous to its 

 entering the working cylinder, should not require a continuous 

 expenditure of heat, or in the case of the steam-engine, the latent 

 heat expended in the boiler should he recovered. 



3rd. That working material is the best which is capable of 

 receiving the largest possible quantity of heat in a given space. 

 Its temperature and pressure should be raised to the highest 

 point which the vessel containing it will admit of, but on leaving 

 the working cylinder, the temperature should be reduced to a 

 minimum. This may be accomplished, either by infinite expan- 

 sion, or practically by the application of a regenerator. 



4th. Losses of heat by radiation and leakage, should be reduced 

 to the smallest possible amount, by working at high pressure and 

 velocity, and by covering all heated surfaces with non-conducting 

 materials. These losses being, proportionally, more to be appre- 

 hended in a perfect, than in an imperfect engine. 



5th. Large and compact heating surface and considerable body 

 of material are essential, to attain a high temperature, without 

 rapid destruction of the vessels. 



6th. No working part of the engine should be brought into 

 contact with highly-heated material. 



The respirator, or regenerator, is undoubtedly a useful agent, 

 for recovering the free, or otherwise unproductive heat of a 

 caloric engine, and the following experimental investigations on 

 its action, by the author, may not be thought devoid of 

 interest. 



The annular space between two concentric cylinders was fitted 

 with 750 brass strips, each 5 feet 9 inches long, and held T Lth of 

 an inch apart from each other, by projecting ribs upon every 

 alternate strip. The internal cylinder contained a piston, with an 

 enlarged hollow piston rod, passing through a stuffing-box, and 

 was worked to and fro by an engine. The lower extremity of the 



