post? the capital of impost is obtained by dividing gh into seven or eight equal parts, and giving one of these from m to n; the width of archivolt 8 0 is equal to one-ninth part of gh; the width of keystone at ef is equal to 08. By drawing lines to e and f from t7 the diverging lines will be obtained.
To assist «the pupil in making out examples of arcades in the other orders, we quote the following /directions of a celebrated author on architecture as to proportions. " The height of arches to the underside of their crowns should not exceed twice their clear width, nor should it be much less; the piers ought not to be less than one-third the breadth of the arch, nor more tjian two-thirds." The pupil desirous of studying the principles of architectural design may consult the work in this Series above noticed.
Example 98, fig- 100, is an elevation of the Tuscan impost, with the heights and projections. The projections are set forward from b to in the line be, the line 5c representing the face of pier corresponding to the line gd in. fig. 99. The scale from which the measurements are taken is that in fig. 62. The figures 1, 2, and 3 denote the width of the mouldings on the archivolt (see fig. 99), and are set back on the line ah from bf
Example 99, fig. 101, is the Doric impost. The heights are measured from the point b on the line be representing the line of pier, as in
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