blocks of stone until it is nearly com-pleted. Centres of this kind are always costly, and affordlittle facilities for easing. 79. Abutments.—The tendency of any arch to overturn itsabutments, or to destroy them by causing the courses toslide over each other, may be counteracted in three ways.1st,… … I y#ifef#^ being thrown on the wing walls, which act as but-tresses (fig. 24.) 3d, where neither of these expedient Fig. 25.
Architecture · Building
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![An illustration from Rudiments of the art of building : represented in five sections [...] for the use of architects, builders, draghtsmen, machinists, engineers and mechanics (1853)](https://img.insideoutlibrary.com/img/200/ia-rudimentsofartof00bull-56-18.webp)
