374

HISTORY OF ENGINEERING.

Book I.

width, and 1 inch in depth, into which oak wedges, somewhat less than 3 inches in breadth,1 inch thick at the head, nearly | inch at the point, and 6 inches long, were introduced.

□ f

Fig. 378.

The mortar used was compounded of blue lias lime and puzzolana, in equal quantities,being prepared by beating it up in a strong wooden bucket made for the purpose, each

E

Fig. 379.

SIXTH COURSE.

mortar beater having his own bucket, which he placed upon any level part of the work,and with a rammer or wooden pestle first beat the lime alone, using a quarter of a peck