150 THE SCIENTIFIC PAPERS OF 



gradually condensed by contact with the water, a partial vacuum 

 will be already formed in the chamber as soon as emptied, whereby 

 the work to be done by the exhauster in then exhausting the 

 chamber will be diminished. In order to prevent the noise which 

 would be caused by the combined jet of steam and air issuing 

 from the open top of the delivery funnel of the exhauster, a 

 " sound killer " S may be placed on the top of the funnel, consisting 

 of a cylindrical metal vessel containing a series of perforated 

 wooden diaphragms ; this contrivance has been found by experi- 

 ment to be very efficient in preventing noise. 



The following are the results of a preliminary experiment made 

 with a rough apparatus for raising water, arranged as shown in the 

 diagram, Fig. 14, Plate 28. The exhauster E was connected by a 

 2-inch pipe F to a closed vessel A capable of holding 10*3 cubic 

 feet, into which the water was raised from varying depths through 

 the suction pipe D of 2 inches diameter. The sectional area of 

 the outer annular air passage in the exhauster used in this 

 experiment was 0'35 square inch, and of the inner air passage 

 in the centre of the jet 0'16 square inch, giving a total of 0'51 

 square inch of air section. "With the sectional area of the 

 annular steam orifice adjusted to (VOS) square inch, and with a 

 steam pressure of 60 Ibs. per square inch in the boiler, the exhauster 

 raised 10'3 cubic feet of water 12 feet high in 40 seconds, and the 

 same quantity 17^ feet high in 75 seconds. With the same area 

 of air section, but with the area of the steam orifice adjusted to 

 0'08 square inch, and with 50 Ibs. steam in the boiler, 10'3 cubic 

 feet of water were -raised 15 feet high in 40 seconds. The height 

 of lift attainable depends upon the pressure of steam employed ; 

 and the quantity of water raised depends within certain limits 

 upon the magnitude of the jet. 



EVAPORATION OF SUGAR. A third application of the improved 

 steam jet is to the evaporation of sugar. In consequence of the 

 remarkable results obtained with this steam-jet exhauster, it is 

 proposed by Mr. R. A. Robertson of London to apply it to sugar- 

 boiling in the West Indies ; and he has communicated to the writer 

 the following notes on the subject. 



The steam-jet exhauster has been employed experimentally 

 with considerable success in exhausting vessels for evaporating 

 liquids in vacuo, and its application for this purpose promises to 



