PREPARATORY MAPS AND DATA 



21 



Fig. i (from Engineering News, Vol. XXIX, p. 242) shows 

 a portable and economical pile-driver for such a purpose. The 

 verticals are made of 2 X 4-inch stuff, and the hammer of a 

 section of an oak or other hard- wood tree which may be growing 



FIG. i. 



conveniently at hand. It may be run on wheels or slid on 

 runners. To hold the uprights steady, snub-lines are pro- 

 vided. The hammer is worked by hand power, three or more 

 men raising and lowering the weight. 



Fig. 2 illustrates a test boring-machine described in Engineer- 



