196 MACHINERY AND TRIALS OF THE PASSENGER SHIPS 
probably was run in this case. It is important to make sure, by cross bearings, that the vessel 
runs through the deep water, which is limited in extent, in both directions. It is important 
also to be sure that the ship is not accelerating when entering the mile, a difficult matter with 
no buoys. 
Torsion meters may have read high; there have been several instances lately where 
these instruments have given readings very disappointing to designers and builders. On the 
occasion of the recent trials of an electrically driven ship the torsion meters were high as 
compared with the electrical instruments, as well as with the self-propelled model results. 
The time out of dry dock is not mentioned, that I noticed, but it is probable that the 
ship was docked, cleaned and painted very shortly before the trials. This time might well 
be given before final printing of the Transactions. 
One troublesome point is absent here; Mr. Warriner tells us that the sea was calm and 
the wind light. These vessels have high superstructures, and it is probable that there is an 
addition of the order of 2 to 2% per cent to be made to the model tank shaft horse- 
power at 19 knots even in still air, the exact amount being difficult to assess. 
Those interested are referred to Commander W. McEntee’s paper read here in 1916, to 
Mr. W. W. Smith’s paper in 1917, also to Admiral Taylor’s classic manual on “Speed and 
Power of Ships,’ 1910. The hull form offers very little air resistance, but the houses, masts, 
etc., in large passenger ships should be allowed for. In the Engineering (London, 1907) 
accounts of the Mauretania’s design, this point is also emphasized. 
Mr. WitiiAm W. Smitu, Member:—There are one or two things in connection with 
Mr. Warriner’s valuable paper that I think can be brought out. Mr. Rigg has already em- 
phasized the fact that the horse-power on the trial course exceeds the estimate results from 
the self-propelled model test by about 12.5 per cent. 
Referring to the test on the President Pierce, given by Mr. Warriner for a speed of 18.08 
knots, the following additional data have been worked out. 
The propulsive coefficient for this speed is 59.8. The superheat referred to by Mr. 
Bailey is 41° F. The ideal water rate, on the Rankine cycle, for the steam conditions on 
that trial is 6.9 pounds per horse-power. The efficiency of the turbines referred to the 
Rankin cycle is 64.5 per cent. The steam consumption of the auxiliaries in per cent of the 
turbine steam consumption is 25.6, and in per cent of the total steam consumption is 20.4. 
If we allow a boiler efficiency of 74 per cent, which is conservative, and take 19,000 
British thermal units per pound for the fuel, the fuel consumption per day works out as 139.7 
tons, and per shaft horse-power per hour, 1.0 pound. The actual evaporation per square foot 
of heating surface is 4.38 pounds. The cooling surface of the condenser per shaft horse- 
power is 1.11 per square foot. This, of course, is satisfactory for temperate water condi- 
tions, but I think it is somewhat low for tropical conditions. At any rate, we usually allow 
from 1.45 to 1.5 square feet per shaft horse-power for tropical conditions, where the tem- 
perature of the water is taken as 85 degrees. 
I am informed that the total weight of the machinery for this installation is 1,040 tons, 
wet, which works at about 180 pounds per shaft horse-power.' 
Referring also to Plate 57 which gives the trial of the President Pierce, it is noted 
that the vacuum as recorded does not agree with the exhaust chamber temperature. In one 
case, the exhaust chamber temperature is recorded as 100.8 degrees and the vacuum as 28.8 
inches. The vacuum corresponding to this temperature is 28 inches, which makes the vacuum 
