364 SECTION MECHANICS. 



by order of Charles the Landgrave, of Hesse-Cassel, with the view o 

 ascertaining how to raise water by the aid of fire. But his experi- 

 ments were interrupted, and he did not resume them until Leibnitz, 

 by a letter of 6th January, 1705, called his attention to what Savery 

 was doing in England, sending him a copy of a London print of a 

 description of Savery's engine. This engine, which of course is well 

 known to you, is illustrated by a model in this collection and now on 

 the table before me. Savery employed a boiler, the steam from which 

 was admitted into a vessel furnished like the sun pump of Belidor 

 with a suction pipe and clack, and a delivery pipe and clack. The 

 steam being shut off, cold water was suffered to flow over the vessel, a 

 partial vacuum was made, water was driven up into the vessel, and 

 was expelled through the delivery pipe upon the next admission of 

 steam, the cocks being worked by hand. This machine came into 

 very considerable use, and was undoubtedly the first practical working 

 steam-engine. It had, however, the defect of consuming a large 

 quantity of steam, as the steam not only came into contact with the 

 cold vessel, but also with the surface of the water in that vessel. 

 Papin, as we know, obviated a portion of this loss by the employment 

 of a floating piston placed so as to keep the steam from actual contact 

 with the surface of the water. I have put a rough diagram of Papin's 

 water raiser on the wall. 



We have in the collection, No. 2007, a cylinder from Hesse-Cassel, 

 said to be of the date of 1699, and to have been intended for employ- 

 ment in Papin's machine ; but it is difficult to say for what part of the 

 apparatus it could have been designed, inasmuch as the cylinder is 

 provided with a flange at one end only, and no means, so far as I can 

 ascertain, exist for closing the other end. You will see from the diagram 

 (as no doubt is already well known to you), that Papin did not pro- 

 pose to condense the steam and by its condensation to " draw up" 

 the water (to use a familiar expression), but intended that the vessel 

 should be charged by a supply from above, and that the steam should 

 be employed only to press on the floating piston and to drive the 

 water out. Papin, however, hoped to use his engine not merely as a 

 water raiser, but as a source of rotary power by allowing the water to 

 issue under pressure from the air vessel, and so as to impinge upon 

 the pallets of a water-wheel and thus produce the required revolution. 



