1898] SOME MORE BOWING EXPERIMENTS 95 



The author regrets that up to the present the only experiment in a 

 racing eight was on an Oxford ' Torpid ' in its early days of practice. 

 He suspects that during a race of eight to ten minutes' duration the 

 power would vary between "3 and - 7 H.P. 



The figure given in the sixth column of the table is of some 

 importance, since it roughly indicates the form of the stroke. This 

 coefficient, found by dividing the mean pull during the stroke by 

 the greatest pull, gives a measure of the uniformity of the pull. 

 If the usual coaching maxim of " getting the full work on at once 

 and carrying it out to the finish," were literally carried out, the 

 stroke diagram would become a rectangle, and the coefficient unity. 



It is, however, probable that the best results would not be 

 obtained with a high coefficient, since the extra work done does not 

 compensate for the additional fatigue, physical and nervous, involved 

 in setting the muscles suddenly at their fullest tension. In addition 

 to this physiological point there is the mechanical one that the 

 efficiency of propulsion is greatest — other things being equal — 

 when the oar is at right angles to the boat, since it is here that the 

 smallest proportion of the work is devoted to generating kinetic 

 energy in the water. 



This question of efficiency of propulsion by oars has been made 

 the subject of experiment by the author. To determine this it is 

 necessary to know, in addition to the information afforded by the 

 indicator diagram, the point about which the oar is turning at 

 every part of the stroke. Since the rowlock is moving forwards, 

 and the tip of the blade backwards, some point between these is 

 neither moving backwards nor forwards. This point may be called 

 the Turning Point. 1 A moment's consideration will show that this 

 point changes its position during the stroke, since the blade first 

 encounters ' dead ' water, so that the blade tip at first moves 

 slowly, and the turning point is lower down the oar than a moment 

 afterwards when the water has been set in motion. 



By attaching a float to different parts of the oar by a string, so 

 that the float was immersed during the stroke, it was possible to 

 estimate fairly accurately the mean position of the turning point, 

 for which a position 36 inches above the tip of the blade was found, 

 i.e., a point only 3 inches above the top of the blade. This shows 

 how comparatively slight is the motion given to the water, a point 

 which will be more clearly brought out below. 



In August of last year the author made an attempt to arrive at 

 more exact results on this point by taking a rapid series of photo- 

 graphs of an oar in motion on the same plate, from a point vertically 

 above the boat. Unfortunately, the only time available, about 3.30 

 p.m. on a cloudy afternoon, was not an ideal one for exposures lasting 



1 It is clearly the projection of the • Instantaneous Centre Locus ' on the oar. 



