will then fall in the tube, till it gets to that height which the atmosphere will sustain.  This is nothing more than the barometer used in all our houses.  If the action of the tube be equal to a square inch, the weight of the column of mercury in the tube would be exactly equal to the weight of the atmosphere on each square inch of surface.  Thus Papin discovered a great step in the steam-engine, though it was not much acted on for some years; he was also the first who proposed to drive ships with paddles worked by steam.

We now come to Thomas Savory, who got a patent in 1698 for a method of condensing steam to form a vacuum.  Savory describes his discovery in this way:—­Having drank a flask of wine at a tavern, he flung the empty flask on the fire, and then called for a basin of water to wash his hands.  A little wine remained in the flask, which of course soon boiled, and it occurred to him to try what effect would be produced by putting the mouth of the flask into the cold water.  He did this, and in a moment the cold water rushed up and filled the flask, this being caused by the steam being condensed and leaving a vacuum, which Nature abhors, and rather than permit this the water rushed up and took the place formerly occupied by the now condensed steam.  We see by this in how simple a way great ends are produced, and in the age in which this happened, the result may be indeed be said to have produced a great end.  The engine of Savory was used for some years as a machine to raise water.  The principle of his engine was just as I have stated, and consisted of two cases and other various parts, and this engine possessed advantages over that of the Marquis of Worcester in sucking up the water as well as forcing.

Savory’s engine consisted of two steam vessels connected to a boiler by tubes; a suction pipe, or that pipe which leads from a pump of the present day to the well, and communicating with each of the steam vessels by valves opening upwards; a pipe going from these steam vessels to any required height to which the water is to be raised.  The steam vessels were connected to this pipe by other valves, also opening upwards, and by pipes.  Over the steam vessels was placed a cistern, which was kept filled with cold water.  From this proceeded a pipe with a stopcock.  This cistern was termed the condensing cistern, and the pipe could be brought over each steam vessel alternately from the boiler.  Now, suppose the tubes to be filled with common air, and the regulator placed so that one tube and the boiler are made to communicate, and the other tube and the boiler closed, steam will fill one of the steam vessels through one tube; at first it will condense quickly, but erelong the heat of the steam will impart its heat to the metal of the vessel, and it will cease to condense.  Mixed with the heated air, it will acquire a greater force than the air outside the valve, which it will force open, and drive out the mixture of air and steam, till