414 THE APPLICATIONS OF PHYSICAL FORGES. [BOOK iv. 



as successfully as to forge anchors, to weave the most delicate fabrics, 

 and to communicate a rapid motion to the heavy millstones of a corn- 

 mill. This also explains how Watt could say, without fear of the 

 reproach of exaggeration, that in case of sickness, in order to avoid 

 the coming and going of servants, he could carry up food to the 

 patient by engines driven by steam." 



The invention of the separate condenser, and of the pumps con- 

 nected with it, was of capital importance, principally from an econo- 

 mical point of view. For an equal effect, it reduced the consumption 

 of fuel to a quarter of that used in Newcomen's engine: The fol- 

 lowing fact, often quoted by the historians of the steam-engine, will 

 give us an idea of the value of the economy immediately effected in 

 mining countries where the pumping engines are worked, and after- 

 wards in all the factories where steam, at low or medium pressure, is 

 employed. Three pumps used to be at work in the Chase water mine, 

 whose proprietors paid Watt and his partner Bolton a royalty for the 

 right of using the condenser. This royalty was fixed at one-third of 

 the value of the coal saved. Now these proprietors thought it to their 

 advantage to redeem these rights by an annual payment of 2,400^. 

 Thus the addition of a Watt's condenser produced in each engine a 

 saving of fuel worth more than 2,400, per annum, or more than 

 7,2 OO/. for the three engines in the mine in question. 



The use of expansion, which Watt had made known, but which was 

 not adopted on a large scale till after Wool if s invention of engines 

 with two cylinders, has increased still more the economy of steam and 

 consequently of fuel the desideratum of all who have attempted to 

 improve the steam-engine. At first only constant expansion was known, 

 but now, fresh arrangements enable us to make the expansion variable. 



We must not, in justice, in the history of the improvements of the 

 steam-engine, mention only the name of Watt. Keane Fitzgerald 

 (1758) was the first who used the fly-wheel to regulate the motion of 

 rotation; and the employment of connecting rods and cranks for 

 transforming the rectilinear oscillating motion of the pendulum, into a 

 rotatory motion is due to Washbrough (1778). Lastly, Murray (1801) 

 was the inventor of the slide-valve worked by the exceutric. For the 

 rest, I shall complete as far as possible this short history of the 

 progress of the steam-engine by describing marine engines, locomo- 

 tives and poi table engines. 



