420 A Resultant System for the [Oct. 



already have the Bailee KM1 bridge, the Kubudduk bridge, and five 

 other bridges of spans varying from 200 feet to 1 20, which were origin- 

 ally constructed on the extreme Taper chain principle, been (as far as 

 was practicable) remodelled on the system I am about to advert to, 

 and most of which have now been erected 3 years, fully proved by 

 previous loading, and subjected to very heavy traffic and storms. It 

 is merely a different application of the uniform chain system, though 

 it partakes of both that and the Taper chain ; I term it " The Resul- 

 tant," indicating thereby that the chains by construction, are in absolute 

 strength, and in the direction of their links, " Resultants" of the 

 tensions due to the adjoining link and auxiliary depending therefrom. 

 It is in fact emphatically a system of equilibrium. The chief differences 

 between it and the old system consist in a modified reduction of the 

 section of iron in the chains from standard to centre, with a correspond- 

 ing increase in the horizontal power in the opposite direction ; in fact, 

 transfering in part the horizontal tension, which, together with the ob- 

 lique, is borne by the chain in the uniform system, to the line of the 

 platform by means of the deviation of the suspending rods from the 

 perpendicular. 



21. In the uniform chain system, as is well known, the suspending 

 rods are vertical. In the "Resultant," they are set at an angle with the 

 roadway, and in proportion to the deviation of this angle from the 

 vertical line, a new element is brought into operation, viz. tension in the 

 horizontal line. This does not affect the principle of construction, but 

 only renders necessary a new distribution of the forces required to sup- 

 port the structure ; this will be evident from the consideration of annexed 

 diagram (Fig. 5.) which represents the principle of the uniform chain, in 

 which the oblique and horizontal tensions are borne by the chain alone, 

 and as these are nearly equal, the power or section of the chain in 

 either direction from point D must be equal also. (See Fig. 5). 



Here the weight of the portion of platform A to be supported is 

 sustained by a single force B, from the main chain C. C. If therefore 

 A=8 tons, the rod B must be equal to that strain. Fig. 6, is an 

 example of the " Resultant" principle, in which the portion (See 

 Fig. 6) of platform weighing, as before, 8 tons, is supported by two 

 forces, viz. the oblique rod B, in the direction b D. and the horizontal 

 force £. Supposing the angle at b to be 30° the rod B. will be strain- 



