ON STEAMSHIP PERFORMANCE. 135 
“TV. The heaviness (or weight of an unit of volume) of the water (64 Ibs. 
per cubic foot of sea-water). 
«V. A factor called the coefficient of friction, depending on the material 
with which the ship’s skin is coated, and its condition as to roughness or 
smoothness, ; 
«The sum of the products of the factors I. and II. for the whole skin of the 
ship is called her augmented surface; and the eddy-resistance of the whole 
ship may therefore be expressed as the product of the augumented surface by 
the factors III., TV., and V., above mentioned.” 
The “ coefficient of propulsion” may be defined as the number of square 
feet of augmented surface which are driven at one knot by one indicated 
horse-power. 
