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point in the direction of the chain or curve, isfound by adding the droop to the length ob-tained from the preceding rule, and multiplyingthis sum by the weight of one foot.

(5) To find the angle which the curve makeswith the vertical. From the sum of the log.radius and the logarithm of the length found inRule 3, subtract the logarithm of the length ofhalf the rope or chain; this will give the log.tangent, of the angle which the curve makeswith the vertical, at the point of support.

If the continuation of the rope or chain overthe point of support, be equally inclined to thevertical as on the side of the bridge—which isvery desirable, in order that the direction of theresultant, or the combined effort of the twoforces, may be vertical, and consequently fallwithin the pier—we shall have these additionalRules :—

(6) The pressure upon each pier is equal tothe weight of the bridge.

(7) The tension, or strain, at the point wherethe chain is fixed to the ground, is equal to thetension at the highest point (Rule 4).

As it appears from Rules 1 and 3 that thelength of the curve is but little affected by themagnitude of the droop, whereas the strain atthe lowest point varies inversely as this droop