( 312 )

very nearly; and, consequently, the greater thedroop, the less the strain in the same propor-tion ; so it is evident that the droop, or versedsine, should be made as great as other circum-stances will permit.

In applying these Rules to the bridge de-scribed at page 302, where the span = 130 feet,the droop =12 feet, the weight of the bridgeunloaded = 12490 lbs., and when loaded withinfantry = 34090 lbs., we shall find

1. The whole length of the curve8 x 12*

= >30 + 3ln3o =132 - 95f “ t -

2. The weight of 1 foot of the bridge,

12490

when unloaded = 132 ^ = 93.94 lbs.

, , , , 34090

when loaded = t t .". or = 256.41 lbs.

3. The strain at the lowest point,when unloaded = 178.04 x 93.94 = 16726 lbs.when loaded = 178.04 x 256.41 = 45652 lbs.

4. The greatest strain, or the strain at thehighest point,

when unloaded = 190,04 x 93,94 = 17853 lbs.when loaded = 190.04 x 256,41 = 48729 lbs.

5. The angle which the chain makes with thevertical at the highest point =» 69°.32'.