McMaster, John Bach, 1852-1932, Making of America Project · New York, D. Van Nostrand · leaf 103
hewhole length of arch is keyed in. Among the varieties of patent centresthat planned by Mr. Frazer, affords amost excellent specimen, and both fromits strength, economy, ease of shiftingand the small amount of space it occupies in the tunnel, has met with muchapproval from the engineering… … FIG. 9. FIG. 8. 99 constructed of four pieces of timber fourand one half in. thick by 16 inches wide,scarfed together as shown in the drawings. In centres of the ordinary construction, the ribs when the laggingsare laid upon them are all of preciselythe same size, and of the same span andrise as…
Bridges · Tunneling
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