240 Kansas Academy of Science. 



B B 



A A 



In this diagram the initial steam pressure, which is the highest 

 pressure realized in the cylinder, is fully maintained up to the 

 commencement of cut-off ; indicating ample size of steam-pipes, 

 ports and other passages in the engine. 



The expansion curve is good, and the release of the steam is 

 sufficiently early to secure a free exhaust, also low and uniform 

 back pressure. 



The exhaust valve closes on the return stroke, in time to provide 

 the necessary compression (or cushion), and thereby counteracting 

 in part the eifects of inertia and momentum of the piston, cross- 

 head, and other reciprocating parts, at the end of the stroke. 



The admission of steam takes place promptly, and projects the 

 admission line to initial pressure at right angles (or perpendicular) 

 to the atmosphere line. These qualities in a diagram are an 

 especial requisite under any circumstances, to insure an economical 

 working engine. 



In practice, however, there will be a great difference in the out- 

 line and appearance of the cards from the different engines, and 

 even from the same engine, arising from numerous circumstances 

 and conditions connected with it. 



The diagram, as before stated, simply shows the pressure of 

 steam existing in the cylinder at each part of the revolution of the 

 engine, and it is the province of the engineer to determine whether 

 these pressures at each and every point are the correct ones, and, 

 if such is not the case, to ascertain wherein the fault lies that causes 

 the error; then determine upon and apply the remedy. 



It must be understood that, in a great majority of cases, the 



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