BRIDGE 



923 



BRIDGE 



earlier one on the same site collapsed while 

 under construction in 1907, presumably because 

 the under side of the cantilever arm was too 

 weak and it buckled, that is, it bent under the 

 enormous compression of the upper half. 



The great advantage of the cantilever bridge 

 is that it can be erected without temporary 

 supports, which might block the channel, or 

 which, as in the case of the huge bridge over 

 the Firth of Forth in Scotland, could not be 

 constructed at all because of the depth of the 

 channel and the swiftness of the current. 

 While this is also true of the suspension bridge, 

 the latter, on account of its tendency to sway, 

 is not strong enough for heavy railroad traffic. 



in all positions. Thus it will be seen from the 

 accompanying picture that in the Canadian 

 Pacific Railway's bridge over the Soo Canal 



OVER THE FIRTH OF FORTH 

 In this graceful cantilever bridge are two 

 spans of 1,710 feet. From 1889 until the com- 

 pletion of the Quebec Bridge these were the 

 longest spans in any structure in the world. 



Movable Bridges. Where river bridges can- 

 not have the roadway high enough for boats 

 to pass beneath them it is frequently neces- 

 sary to make them movable. The most usual 

 type of this class of bridge is the swinging 

 drawbridge, which turns upon a vertical axis, 

 like a merry-go-round. Sometimes, however, 

 the central pier necessary for a swinging bridge 

 would occupy space in the stream that is 

 needed for ships. In this case a lift bridge 

 which can be raised like an elevator, a bascule 

 bridge opening like a jack-knife, or a ferry 

 bridge consisting of a car traveling back and 

 forth suspended from a track high overhead 

 may be suitable. In both the lift and the 

 bascule bridges massive counterweights move 

 down when the bridge goes up so that, like a 

 window and its weights, the whole structure 

 is always balanced and requires very little 

 power to move it. In a bascule bridge the cir- 

 cular swing of the two lever-like halves makes 

 it very difficult to maintain perfect balance 



BASCULE BRIDGE 



Canadian Pacific Railway Bridge over the canal 

 at Sault Ste. Marie. When raised, it provides a 

 navigation clearance of 279 feet. Over all, the 

 bridge is 426 feet in length and is credited with 

 establishing a record in this type of construction. 



the counterweights swing inward as the bridge 

 opens. 



Pontoon Bridges. A bridge built on boats is 

 called a pontoon bridge. It is usually a tem- 

 porary structure erected by an army. Perhaps 

 the most famous pontoon bridges were those 

 by which the hordes of Xerxes crossed the 

 Hellespont. C.H.H. 



BRIDGE, a game of cards played with the 

 full pack of fifty-two cards, and usually by four 

 people. It is derived from whist, and was 

 formerly called bridge whist. The game is 

 of uncertain origin; similar games were played 

 a century ago in Russia, Turkey and Denmark, 

 but its popularity dates from 1894 and 1895, 

 when it was introduced in London. Since 

 then various new rules and styles of play have 

 been introduced from time to time. The most 

 important of these variations is the game of 

 auction bridge, whose popularity has been 

 steadily increasing since its introduction in 

 1907. It has now completely supplanted ordi- 

 nary bridge in public favor. Both in regular 

 bridge and in auction bridge the tendency at 

 first was to adhere rigidly to certain rules, but 

 as the games developed greater freedom was 

 allowed to the players. Bridge, however, is 

 still an exacting game, and no beginner can 

 expect to master it easily. Power of concen- 

 tration and a retentive memory are required 

 to a considerable degree, but the best equip- 

 ment of the bridge player is experience. Prac- 

 tice is the best teacher, but the beginner is 

 advised also to accept advice from better play- 

 ers and to consult at least one of the standard 

 books mentioned at the end of this article. 



Regular Bridge. The play in bridge is sim- 

 ilar to that in whist, except that the dealer 

 or his partner must declare the trump. The 



