A/A' \\-II.IJ.\M .S7/.M//..\'.V, I-.R.S. 157 



D jet for removing dust from the casing of millstones daring 

 the grinding might be attended with in><><l ivsnlis ; hut it must 



-ni'd that the jet acted at a disadvantage when producing 

 only a small degree of exhaustion or compression, though this 

 tlisadvanta^'- might to a certain extent be obviated by reducing 

 the area of the jet orifice when the work was below the capabilities 

 of the full jet. For as the surface of contact between the steam 

 and air determined the work done, and the quantity of steam of a 

 iriven pressure in the jet in proportion to the air determined the 

 of vacuum or compression produced, it followed that, in 

 to work economically, the area of the steam orifice ought 

 to increase gradually as the vacuum or compression increased. 

 Under any circumstances however the jet would be to some extent 

 less advantageous when producing only a small degree of vacuum, 

 because the difference of velocity between the steam and the air, 

 which was productive of eddies, was then greater than when an 

 equal weight of air was discharged from a higher degree of vacuum, 

 a larger proportion of the velocity of the steam being utilised in the 

 latter case for overcoming the greater excess of pressure of the 

 external atmosphere. The steam jet had not yet been applied for 

 producing the air blast for millstones, but no doubt it might be 

 employed advantageously for that purpose. 



In the discussion of the Paper 



" ON THE EJECTOR CONDENSER FOR STEAM-ENGINES 



DISPENSING WITH AN AIR-PUMP," 



By Mr. ALEXANDER MORTON, 



The PRESIDENT (MR. C. WILLIAM SIEMENS) * considered that, 

 ingenious as the ejector condenser was, its efficiency might be 

 materially augmented by increasing the extent of surface of the 

 water jet for condensing the steam. The condensing surface was 



* Excerpt Minutes of Proceedings of the Institution of Mechanical Engineers, 

 1872, p. 270. 



