65

Hence, such a pier ought to be con-structed with courses having a vertical bond,either by dovetailing, joggling, or by layingthe courses so as to produce one solidblock. But if the pier be built in the or-dinary manner, without vertical bond, thenit m^y, hi the words of Mr. Emerson, beSaid to be built of loose materials; andthen, in such a case, it Would be better thatthe bearing pier should be 159 feet wide,or 163 feet, as obtained from the paraboladr catenary.

But,in no case need the pier be solid; itmay be hollow* perpendicularly or hori-zontally, it may have wells in it or archesthrough it.

If the horizontal draft be resisted by theland rebutments wholly, that is, if thebearing piers be considered wholly bearingpiers, then the tops of the bearing piersshould be made Upon the principle of arailway, so that there may be as littlefriction between the chains and the bed onwhich they lie as possible; perhaps thechains should lie on rollers.

F