cast-iron framed piece two feet long and five feet in depth, and these
were bolted together. The Southwark bridge over the Thames, by Sir
John Rennie, followed, in which a similar principle of construction is
adopted. There is much to be said in favor of a system which puts each
rib under compression in the manner of a stone arch, and which builds up
a rib from a number of small pieces. At least, it is a system based on
the legitimate use of cast iron for constructive purposes. The large
segmental castings used in the Pimlico bridge, and the new bridge
over the Trent at Nottingham, from Mr. M. O. Tarbotton's design, are
excellent examples of the arched girder system. The Nottingham bridge
has each rib made up of three I-shaped segments bolted together and
united transversely; the span is 100 feet in each of the three openings,
and the ribs are three feet deep at the springing, diminishing about six
inches at the crown. We have yet to learn why engineers have abandoned
the arched bridge for the wrought iron girder system, except that the
latter is considered more economical, and better fitted for bearing
tensile stress. Cast-iron bridges constructed as rigid arches, subject
to compression and composed of small parts, have all the mechanical
advantages of stone without some of its drawbacks, while artistically
they can be made satisfactory erections.--_Building News_.

* * * * *




SIR W. PALLISER.


We announce with regret the death of Major Sir William Palliser, which