126 ]\cio Improveyncnts on Steam- Engines. 



pable of bearing the requisite heat without being converted 

 into vapour, 



" By this arrangement, and method of applying the sur- 

 rounding heat, I not only obviate the necessity of employ-- 

 ing steam of a great expansive force round the steam vessel 

 or vessels, or tliL- working cylinder or cyhnders, as already 

 mentioned, to maintain them at the temperature required, 

 but I am enabled to obtain from steam of a comparatively 

 low temperature, or even from water itself admitted into 

 the steam vessel or vessels, all the effects that can be ob- 

 tained from steam of a high temperature, without any of 

 the risk with which the production of the latter is accom- 

 panied, not only to the boiler and other parts of the ma- 

 chinery, but even to the hves of the workmen; for such 

 low steam, or even water, (but 'in every case ateam is pre- 

 ferable,) being admitted into a steam vessel or vessels, or 

 working cylinder or cvlinders, kept at the requisite higher 

 temperature by the foremcntioned means, will there be ex- 

 panded in any ratio required, and produce an effect in the 

 working of the engine which cannot otherwise be obtained 

 but at a greater expense of fuel, or with the risk of an ex^ 

 plosion. By this means I can make use of steam expanded 

 in any required ratio, or of any given temperature, without ► 

 the necessity of ever having the steam of any greater elas- 

 ticity than equal to the pressure of tlie common atmo- 

 sphere. 



" Another improvement which I make use of in steam- 

 engines consists in a method of preventing, as much as 

 possible, the passage of any of the steam from that side of 

 the piston which is acted upon by the said steam to the 

 other side which is open to the condenser; and this I ef- 

 fect, in those steam-engines known by the name of double 

 engines, by employing upon or above the piston mercury 

 or fluid metal, or metals in an altitude equal to the pressure 

 of the steam. The efficacy of this arrangement will appear 

 obvious, from attending to wiiat must take place in working 

 such a piston. When the piston is ascending, that is^ 

 when the steam is admitted bLJow the piston, the space on 

 its other side being open to the condenser, the steam en- 

 deavouring to pass up by the side of the piston is mot and 

 effectually prevented by the column of metal equal or su- 

 perior to it in pressure, and during the down stroke na 

 steam can possibly pass without first forcing all the metal 

 through. In working what is called a single engine, a less 

 considerable »hitude of metal is required, because the steam 



always 



