2G0

HISTORY OF ENGINEERING.

Book I.

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Fig. 26G. SECTION OF THE CASSOON.

4 inches thick, laid longitudinally, and crossing at right angles those previously laid; thusthe bottom became 14 inches thick, and the superficial area of the base 11 f>0 square feet.

The height of the sides was 1G feet above the bottom, and composed of 24 squaredtimbers, the scantling of which was 9 by 6 inches, laid on edge; these were of oak, and thelength of each course was 72 feet; at the angles they were lapped one over the othereach two courses were alternately pinned together, making one solid mass.

To strengthen the angles, the timbers were doubled, pieces 4 inches in thickness beingplaced vertically ; one in the angles, 18 inches in width, between two others 12 inches in

Fig. 267.

JOINTS OF THB CARPENTRY OF T'HE CAISSOON.

width, well pinned into the outer timbers, the wedge being driven into the heads of thepins to render them more secure.