SECT. I.] 



THE STEAM ENGINE. 



13 



though he was not distinguished by the novelty of his views, yet the sound 

 knowledge he had of science seems to have been of more real advantage to those 

 who sought benefit from the steam engine, than the undirected efforts of his 

 predecessors. 



1720. LEUPOLD. 



12. About this period various writers gave notices of the different engines 

 that had appeared ; but those who added nothing, either in theory, experiment, or 

 construction, it would be as tedious as useless to notice. But in this class, Leupold, 

 the industrious German collector of mechanical inventions, ought not to be placed, 

 he having given the first sketch for a high-pressure engine with a piston ; it is 

 further remarkable as having a four-passage cock for the admission and emission of 

 steam. 



The scheme of Leupold is simple : over a boiler B, he placed two cylinders C C, 

 fitted with steam-tight pistons, pp. A four-way steam-cock, S, is placed between 



FIG. 5. 



the boiler and cylinders, so as to alternately admit steam into one cylinder, and let 

 it out from the other. The piston, by the admission of strong steam from the 



density and temperature which it had in the cylinder at the termination of the stroke ; but this tem- 

 perature and density not being ascertained, the experiment does not show the bulk corresponding 

 to the atmospheric pressure ; for the elastic force in the boiler differs considerably from that m 

 the cylinder. 



