ABC OF THE STEEL SQUARE 115 



the pitches differ the major axis ceases to be 

 parallel; and the greater the difference in the 

 pitches, the greater will be the difference in 

 the axis and diagonal line. This fact can be 

 easily demonstrated by cutting a model bed block 

 out of 2-inch by 2-inch stuff to equal pitches. 

 Procure a board, and draw a parallel line, say 

 8 inches off the edge. Now square over a line 

 to cut the first line; set the bed block on, witk 

 the back corner touching the intersection of the 



Fig. 78. 



lines. Lay a piece of cardboard on the inclined 

 face of the bed block, and let it slide down until 

 it touches the board. Make a mark along this 

 edge, and it will be seen, on removing the card, 

 that this line is equidistant from the corner (see 

 Fig. 78). In Fig. 78 the cardboard is shown 

 as though it were transparent. What has just 



