698 TRANSACTIONS OF THE 



Mr. Stetston — If steam is worked at one pressure throughout 

 the entire stroke, the engines may be made lighter — a principal 

 advantage of very high pressure and expansion. 



Mr. Leonard remarked that the crank and shafting pins, &c., 

 were in size and weiglit proportioned to the velocity with which 

 the parts were moved. 



Mr. Pell made the following remarks on the advantages of the 

 High Pressure Engine, and principal objections to it : 



First we will consider the advantages. They are infinitely 

 more simple than the low, and in proportion to their power 

 are smaller and of less weight, consequently less costly, and 

 less expensive to maintain in action, are more compact, and 

 require less room. The cylinder is smaller in diameter for an 

 equal power; and the length of stroke may be less, condensation 

 not being required, the velocity of the piston is greater, which 

 diminishes the weight and dimensions of tlie fly wheel, and the 

 heavy apparatus of the condensing engine is not required in the 

 high-pressure one. The air pumps, hot and cold water pumps, 

 are dispensed with, as well as the expensive arrangements for 

 condensing water. Many pistons and valves requiring constant 

 attention to keep them tight, are unnecessary in the high pres- 

 sure engine; saving materials for packing and lubrication. The 

 various parts are less clumsy, and the engines necessarily more 

 portable, and their erection becomes more easy. This latter 

 qualification has caused their exclusive use for locomotives, and 

 is the reason why Mr. Fisher uses it in his steam carriage. 



It may be as well to state that the above enumerated advan- 

 tages apply solely to the engines, and do not refer in the same de- 

 gree to the boilers. The dimensions of these do not follow the 

 smaller size of the cylinder in the same proportion ; but as a 

 smaller quantity of water is required to be evaporated, they have 

 their advantages when properly constructed. Another great ad- 

 vantage is that the high-pressure engine sustains much less loss 

 from friction ; it does, not require the constant supply of cold 

 water, necessary for condensation, which is an immense advantage 

 in warm climates, where it is difficult to obtain water sufficiently 



