ENCLOSING DAMS. 63 



pieces. The horizontal side timbers were clamped firmly to- 

 gether at the rear end with a distance-piece 12 inches thick 

 between them. Two ordinary tackles were made fast to the 

 smaller or rear ends of the horizontal side pieces to serve as 

 lateral guys, and a 0-inch hawser to the forward end, near the 

 oak block. The apparatus was next weighted with iron ballast 

 laid across the side pieces until it sank promptly ; it was then 

 ready for use. 



The method of applying this apparatus is as follows : 



X 



. \ 



| Ml IT 



FIG. 46. 



assuming a pile to have been driven and the pile-driving 

 machine to be in a proper position for driving another pile 

 in the line, the " spider " is advanced so that the two side 

 pieces or horns of the machine are made to pass one on either 

 side of, and clasp the sheet-piles already driven. The hawser 

 is then drawn taut until the oak throat block presses hard 

 against the pile last driven, and the lateral side guys properly 

 secured are drawn up by the men on the platform until the 

 machine below is in proper line, which is readily known if the 

 hangers are vertical. All being adjusted, a sheet-pile is raised 



