SINGLE V. TWIN-SCREW PROPELLERS.

Grey River Argus, Volume XII, Issue 1390, 14 January 1873, Page 2

SINGLE V. TWIN-SCREW PROPELLERS.

The Royal Mail Company's steamship Liffiy, Captain E. West, which was to leave Southampton on Monday, as the third vessel of this company's additional line of steamers to Brazil and River Plate, was tried at the measured mile in Stokes Bay on Saturday. With an average pressure of 601 bof steam, vacuum 26in, and engines making 76 revolutions per minute, the measured mile was run four times with the following rests :— lst ran, 4min 22sec, or 13.740 knots per hour ; 2nd ran, 4min 44sec, or 12 676 knots ; 3rd ran, 4min 21sec, or 13,793 knots ; 4th run, 4min 44sec, or 12.676 knots, the common mean speed being 13.221, and the Government average 13.227 knots per hour. A special interest is attached to this vessel, as she was formerly a twin-screw— that is, she was propelled by two screws, one on each counter, and her trial was then considered to prove that this system showed an undoubted advantage over the ordinary one of a single propeller. The Liffey was originally bnilt for the New Zealand and Pacific Company, and ran between Panama and New Zealand for three or four years, her name then being the Pauline, and did her work very satisfactorily. She is now the property of the Royal Mail Company, who changed her name to the Liffey, and intrusted the work of altering her hull, fitting new compound enaines, and substituting a single for | the twin-screws, to Messrs Day., Summers and —thai ' Tue "Jesuits "obtained under the two systems are shown as follows : — Twin-screw date of trial, August 8, 1865 ; mean speed' 12.374 knots; indicated horse-power, 1620., hingle screw, date of trial, October 12, 1872; mean speed, 13.227 knots ; indicated horsepower, 1540. The single-screw engines are 300-horse power nominal, and those of the twin-screws were 350 ditto. The Liffey has now Btowage capacity for 300 tons more cargo than before, and consumes 20 tons of coal per day, against 34 tons when on the old system.