460 Additional Notes. 



Steam-Engines, p. 47. 



*' The expansive force of steam was known, in some de- 

 gree, to the ancients. Hero, of Alexandria, describes an 

 application of it to produce a rotative motion by the re-action 

 of steam issuing from a sphere mounted upon an axis, through 

 two small tubes bent into tangents, and issuing from the op- 

 posite sides of the equatorial diameter of the sphere; the sphere 

 was supplied with steam by a pipe communicating with a pan 

 of boiling v/ater, and entering the sphere at one of its poles. 



*' A French writer, about the year 1630, describes a me- 

 thod of raising water to the upper part of a house, by filling 

 a chamber with steam, and suffering it to condense of itself; 

 but it seems to have been mere theory, as his method was 

 scarcely practicable as he describes it. In 1655, the Mar- 

 quis of Worcester mentions a method of raising water by 

 fire, in his Century of Inventions; but he seems only to have 

 availed himself of the expansive force, and not to have known 

 the advantages arising from condensing the steam by an injec- 

 tion of cold water. This latter and most important improve- 

 ment seems to have been made by Capt. S A very, some time 

 prior to the year 1698, for in that year his patent for the 

 use of that invention was confirmed by act of parliament. 

 This gentleman appears to have been the first who reduced 

 •the machine to practice, and exhibited it in a useful form. 

 This method consisted only in expelling the air from a vessel 

 by steam, and condensing the steam by an injection of cold 

 water, which making a vacuum, the pressure of the atmos- 

 phere forced the water to ascend into the steam-vessel through 

 a pipe of 24 to 26 feet high, and by the admission of dense 

 steam from the boiler, forcing the water in tlie steam-vessei 

 to ascend to the height desired. This construction was de- 

 fective, because it required very strong vessels to resist the 

 force of the steam, and because an enormous quantity of 

 steam was condensed by coming in contact with tlie cold wa- 

 ter in the steam-vessel. 



" About, or soon after that time, M. Papin attempted a 

 steam-engine on similar principles, but rather more defective 

 in its construction. 



" The next improvement was made very soon afterwards 

 by Messrs. Newcomen and Cawley, of Dartmouth: it 

 consisted in employing for the steam-vessel a hollow cylinder, 

 shut at bottom and open at top, furnished with a piston slid- 



