1424

THEORY AND PRACTICE OF ENGINEERING.- Book II.

a model for construction,but a school for the studyof the mason’s art; itsgeneral arrangement, andthe proportion of its piersand walls, were no doubtmost useful guides to thebuilders of the middleages. There is scarcely apeculiarity in masons’work of which an examplemay not be found admi-rably effected amidst thecorridors or vaultings ofthis edifice ; and the testto which its stability hasbeen subjected during nearly 2000 years is aconvincing proof that every point in its construc-tion was well considered, and must impress uponus the rather humiliating conviction that masonryhas not progressed beyond the knowledge ac-quired by theancients.

i

^ X

ISODOMON,

l'ig. 2405.

Cramps of metal, either ironor bronze, were much used bythe ancients for uniting onestone with another, and weresometimes run with lead. Theholes in the walls of the Co-liseum and other monumentsat Rome were drilled or cutfor the purpose of extractingcramps of bronze that unitedthe courses of masonry toge-ther : in the Parthenon atAthens the writer found oakdovetails applied for thesame purpose. An excellentmethod of uniting a course ofsione is by forming a triplerange, notching one into the

isooomon.

Fig. 2406,

L