All About Engines

44 All About Engines not condensed by the cold of the condenser, and may impede the working of the engine, it is to be drawn out of the steam vessels or condensers by means of pumps, wrought by the engines themselves, or otherwise. “ Fourthly, I intend in many cases to employ the expansive force of steam to press on the pistons, or whatever may be used instead of them, in the same manner as the pressure of the atmosphere is now employed in common fire engines. In cases where cold water cannot be had in plenty, the engines may be wrought by this force of steam only, by dis- charging the steam into the open air after it has done its office. “ Lastly, instead of using water to render the piston or other parts of the engines air and steam tight, I employ oils, wax, resinous bodies, fat of animals, quicksilver, and other metals in their fluid state. “And the said James Watt, by a memorandum added to the said specification, declared that he did not intend that anything in the fourth article should be understood to extend to any engine where the water to be raised enters the steam vessel itself, or any vessel having an open communication with it.” From the point of view of construction the really important feature of the invention was the sepa- rate condenser and air pump—and the air pump was essential. The water which formed in the con- denser could have been got rid of by connecting it with a pipe leading to a well rather more than 34 feet