THE EFFECT OF WAVES UPON A TAFFRAIL LOG. 129 
were held last spring, the log was again towed. ‘These trials were not quite 
as satisfactory as those on the Gresham, as there was considerable wind and 
tide, but the mean curve of speed on R. P. M. is given on Plate 63. The log 
was towed about 133 feet astern as it was impossible to have it farther astern 
without trouble on the turns, and Fig. 9 shows the wave formation at the 
speeds corresponding to the maxima. 
Fig. 10 shows the effect on the log to be expected from the stern system 
only. Fig. 11 shows the effect of the combined bow and stern systems, 
Fig. 12 shows this latter plotted about the normal calibration of the log 
unaffected by waves. Table III gives the results of the trials and Fig. 13 
shows the curve derived in Fig. 12 superposed on the experimental points. 
x2 
. 
Another point is interesting, and that is the amount of the deviation 
on either side of the still water-line and this is shown by the amplitude of the 
calibration curve. For the Gresham it varies about six or seven per cent. 
