PREPARATION OF THE DESIGN 105 



an advantage to see both sides at once. The figure 

 is then an ordinary straight sided one, to be dealt 

 with by ordinary methods. 



The area of a circle can be arrived at by several 

 ways, of which the two simplest are : (i) Multiply 

 the square of the diameter by -78. (2) Multiply 

 the square of the radius by 3| or more roughly by 

 3. Suppose a circle whose diameter is 6 ft. By 

 the first method 6 2 = 36 ; 36 X -78 = 28-08. By 

 the second method 3* = 9 ; 9 X 3] = 28f . When 

 the diameter is an exact number of feet the latter 

 is the quicker method. 



The area of a winding path or bed with parallel 

 sides is easiest found by stepping along the centre 

 a pair of dividers opened out to represent 10 or 

 20 ft. This finds the length, which multiplied 

 by the uniform width gives the area. 



Solid contents are required when working with 

 levels to find amount of soil to be shifted. In a 

 rectangular body its cubic contents are obtained 

 by multiplying length by breadth and again by 

 height. When land is on a uniform slope a figure 

 equivalent to half a rectangular is formed, the 

 depth being taken from so many feet at one end 

 to nil at the other. An undulating surface can be 

 equalized in the same manner recommended for 

 dealing with offsets. 



