lea? U. S$. COAST AND GEODETIC SURVEY 
scale would indicate the square of the velocity. A special square-root 
reading scale for taking the velocities direct from the marigram may 
be prepared as follows: Let }’=distance of any velocity graduation 
from zero of scale. Then 
Y (an inches) =0.1 X (scale factor) < (gear ratio) X (velocity)? (480) 
With the scale factor and gear ratio each unity, 1 knot of velocity 
would be represented by 0.1 inch on the marigram, 2 knots by 0.4 
inch, 3 knots by 0.9 inch, etc. With a scale thus constructed the 
velocity of the tidal current may be taken directly from the mari- 
gram. Any nontidal current which is to be included may afterward 
be applied. 
