curve, such as we know to be essential, by employing a great number of distributions of individually small magnitude.
But it is evident that each component distribution should in itself obey the conjugate law, hence we may formulate a rule for laying out the load grading curve as follows:—
On the efficiency curve (Figs. 126, 127), cut off by a horizontal line, the portion of the curve defined by the maximum blade limits selected.
Divide the maximum ordinate of the part so cut off (Fig. 133)
into some convenient number of equal parts,
Fig. 133. and draw horizontal lines cutting the efficiency curve at Draw a number of lines through the origin 0, making small angles with the axis of and with one another, to represent the component increments of the thrust grading distribution, and drop perpendiculars from the points to indicate the limits of each increment.
Through the intersections of the perpendiculars let fall, and the inclined lines drawn through the origin, draw the thrust grading curve.
It will be noted that the angular increments of the thrust distribution (the angles between the lines passing through the origin) need not bo equal to one another; it may be considered within the province of the designer to vary these as he may think fit. In general, owing to the desirability of utilising as
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