363 SECTION MECHANICS. 



the pit, which was 276 feet deep, and that each pump delivered into a 

 leaden cistern from which the pump above it drew. 



After having given a most accurate description of the engine, 

 Belidor breaks out into a rhapsody and says (I will give you a free 

 translation) : " It must be acknowledged that here we have the most 

 marvellous of all machines, and that there is none other of which the 

 mechanism has so close a relation to that of animals. Heat is the 

 principle of its movements ; in its various tubes a circulation like that 

 of the blood in the veins is set up ; there are valves which open and 

 shut ; it feeds itself and it performs all other functions which are neces- 

 sary to enable it to exist." 



Smeaton employed himself in perfecting and in properly proportioning 

 the Newcomen engine, but it was not until James Watt that the next 

 great step was made. That step was, as we all know, the doing away 

 with condensation in the cylinder, the effecting it in a separate vessel, 

 and the exclusion of the atmosphere from the cylinder. These altera- 

 tions made a most important improvement in the efficiency of the 

 engine in relation to the fuel consumed ; but they were so simple that 

 I doubt not if examiners into the merits of patents had existed in those 

 days, Mr. Watt would have had his application rejected as being 

 " frivolous." We have here from case No. 1928, a model made by 

 Watt, which appears to be that of the separate condenser and air 

 pump. We have also 8, which is a wooden model made by Watt ot 

 a single acting inverted engine having the top side of the cylinder 

 always open to the condenser, and a pair of valves by which the 

 bottom side of the piston can be put into alternate connexion with the 

 boiler and with the condenser, the contents of which are withdrawn 

 by the air pump, 3/5. From the same case is a model of a direct acting 

 inverted pumping engine made in accordance with the diagram ; 8, 

 ib, is a model of Watt's single acting beam pumping engine, while ib 

 is a model of Watt's double acting beam rotary engine. lob, from the 

 same case, is Watt's model of a surface condenser. To Watt we owe 

 condensation in a separate vessel, exclusion of the air from the 

 cylinder, making the engine double acting, employment of the steam 

 jacket, employment of the steam expansively; the parallel motion, 

 the governor, and, in fact, all which made Newcomen's single acting 

 reciprocating pumping engine into that machine of universal utility that 



