The most notable invention of latter days in bridge construction is that of the cantilever bridge, which is a system devised to dispense with staging, or false works, where from the great depth, or the swift current, of the river, this would be difficult, or, as in the case of the Niagara River, impossible to make. The word cantilever is used in architecture to signify the lower end of a rafter, which projects beyond the wall of a building, and supports the roof above. It is from an Italian word, taken from the Latin _cantilabrum_ (used by Vitruvius), meaning the _lip of the rafter_. If two beams were pushed out from the shores of a stream until they met in the centre, and these two beams were long enough to run back from the shores until their weight, aided by a few stones, held them down, we should have a primitive form of the cantilever, but one which in principle would not differ from the actual cantilever bridges. This is another American invention, although it has been developed by British engineers--Messrs. Fowler & Baker--in their huge bridge now building across the Forth, in Scotland, of a size which dwarfs everything hitherto done in this country, the Brooklyn bridge not excepted.
The first design of which we have any record was that of a bridge planned by Thomas Pope, a ship carpenter of New York, who, in 1810, published a book giving his designs for an arched bridge of timber across the North River at Castle Point, of 2,400 feet span. Mr. Pope called this an arch, but his description clearly shows it to have been what we now call a cantilever. As was the fashion of the day, he indulged in a poetical description:
"Like half a Rainbow rising on yon shore, While its twin partner spans the semi o'er, And makes a perfect whole that need not part Till time has furnish'd us a nobler art."
[Illustration: View of Thomas Pope's Proposed Cantilever (1810).]
The first railway cantilever bridge in the world was built by the late C. Shaler Smith, C.E., one of our most accomplished bridge engineers. This was a bridge over the deep gorge of the Kentucky River.[7] The next was a bridge on the Canadian Pacific, in British Columbia, designed by C. C. Schneider, C.E. A very similar bridge is that over the Niagara River, designed by the same engineer in conjunction with Messrs. Field & Hayes, Civil Engineers. This bridge was the first to receive the distinctive name of cantilever.
