92 



NATURAL SCIENCE 



[August 



In order to prevent the necessary length of the strip being 

 excessive, the diagrams are made to overlap (Fig. 2). If the strokes 

 are flat at the top it is frequently not easy to determine at sight 

 which is the ' finish ' corresponding to a particular ' beginning.' This 

 is, however, discovered at once by measuring the length of the first 

 or last stroke, from which the approximate distance of the ' finish ' 

 from any ' beginning ' is known. A stroke thus individualised can 

 then be measured up. The measurements taken are : — 



(1) Length of stroke in degrees: which is afterwards reduced 

 to distance moved through by the handle of the oar. 



(2) Greatest height of diagram. 



(3) Area, measured with an Amsler planimeter. 



(4) The shape of the curve gives the style of stroke. 



No.22 



Easy 



3.R. 



Fig. 2. Part of an Indicator Card (two-thirds actual size). 



Fig. 3. Deduction of Characteristic Diagram (actual size). 



To determine the style of an oarsman under any particular 

 circumstances, the idiosyncrasies of the strokes are eliminated by 



superposing several 

 diagrams (Fig. 3), 

 and then drawing a 

 mean line through 

 the result. In this 

 way the ' Charac- 

 teristic Diagram ' 

 is obtained. Simi- 

 larly, in finding 

 an oarsman's power, 

 the mean of several stroke measures is taken. 



Having now described the indicator, the diagram, and the 

 method of treating it, some account will be given of the results 

 obtained from twenty-seven experiments involving some 2000 

 strokes of rowing. The principal oarsmen experimented on are 

 denoted by A, B, C, D, E, F, G, H, I. 



Fig. 6 represents a series of characteristic diagrams of rowing 

 on sliding seats. K was obtained with the earlier indicator, but 

 is introduced here as the stroke-form differs from any others in no 

 small degree. This stroke although very short is nevertheless very 

 powerful. 



