132 THE EFFECT OF WAVES UPON A TAFFRAIL LOG. 
Diameter low-pressure cylinder............ 56¢ in. 
Stroke, all pistons............ Fe Rae neath Nis 30 in. 
Diametenolpropellers aa: peer are ere 10 ft., o in. 
nitchvol propellers) hae ey a erst WA) Heo, (S ia, 
TABLE V.—STEAMER SANKATY. 
Principal Dimensions. 
Lengthvover allang iene ees eee ee oe 195 ft., o in. 
Weneth) be Ps (Ae Pxatmudder post) eee. 188 ft., o in. 
Beam moulded at 8 ft.o in., normal water-line. Bit iho, GD ral, 
Beam Over cuandSe sey eaten 27 ibs) © Wn, 
Depth mouldediee yen sea en eee 12 ft., 6 in. 
Dratt meanmitollded er an sere en 8 ft., o in. 
Displacement to 8 ft., oin. normal water-line. 688 tons, S.W. 
Wetted surlace a3 cua een ees 5,700 sq. ft. 
DISCUSSION. 
VICE-PRESIDENT McFarLanp:—Gentlemen, you have heard the paper on 
‘‘The Effect of Waves Upon a Taffrail Log,” by Prof. Harold A. Everett. Dis- 
cussion is now in order. 
PROFESSOR WM. HovcaarpD, Member:—This paper has the rare merit of being 
of direct practical influence, and will no doubt prove of importance to navigators 
and shipbuilders. I find nothing in it to criticise, but will only make a few 
additional remarks. 
The magnitude of the deviation of the log factor on either side of its still-water 
value is a function of the height of the waves, as stated in the paper. Now, this 
height must depend upon the size and form of the ship, and will presumably increase 
with the depth and fullness. For large ships of full form, offering great wave resist- 
ance, we may therefore expect to find the greatest fluctuations in the log factor. 
There is another source of error in the log of similar character to the one here 
discussed, viz., due to the ordinary sea waves. Suppose first the sea runs in the 
same direction and with the same speed as the ship, we shall then have, theoretically, 
a constant reinforcement or weakening of the wave system produced by the ship, 
with a corresponding influence on the log factor. “The same will be the case even 
