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round it is ſupplied with Steam from the Boiler; and that which has performed its Office may either be diſcharged by means of Condenſers, or into the open Air.
Sixthly, I intend in ſome Caſes to apply a degree of Cold not capable of reducing the Steam to Water, but of contracting it conſiderably, ſo that the Engines ſhall be worked by the alternate Expanſion and Contraction of the Steam.
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.
In Witneſs whereof I have hereunto ſet my Hand and Seal, this Twenty-fifth Day of April, in the Year of our Lord One Thouſand Seven Hundred and Sixty-nine.
JAMES WATT, (L. S.)
Sealed and delivered in the Preſence of
COLL. WILKIE.
GEO. JARDINE.
JOHN ROEBUCK.
Be
