376

HISTORY OF KNGINEER1NG.

Book I.

through the upper hole, drove stiffly into the lower ; after driving as far as possible, a saw-cut was made in the end to the depth of a couple of inches, into which a wedge, of £ inch

Fig. 381. SEVENTH COURSE.

in thickness at bottom, and double that at the square end, was driven. Each trenail wasthen cut off even with the top of the stone, and its upper end wedged cross and cross.

n E

Fig. 382. FOURTEENTH COURSE.