402 MENAl BRIDGE. 



■f 2176 = 4129 tons for the whole vertical 

 pressure on the pier. 



Subtracting equation (4) from (3) gives 

 6742 — 6674 = 68 tons = horiz. force caused 

 by the inequality of the angles 16^* 10' and 

 18^. 3', and supported only by the pillar which 

 it tends to draw in direction AD. This force 



CO 1 



however is but ^-^29 == qj^ th of the vertical 

 pressure upon the pillar. 



The deflection of the force down the piljar, 

 from the vertical line, is half the difference of 

 the angles, 18°. 3' and 16^ 10', = 57': therefore 

 the deviation from the vertical at 171 feet from 

 the top is 171 X nat. tan. 57' =: 171 x .01658 

 == 2.83 feet, or less than a yard at the surface 

 of the water* 



The ends of the chains of this unrivaled 

 structure are, at the Anglesea side at least, 

 fastened deeply in a rock that has never 

 been removed. There seems then no proba- 

 bility that it would fail first in that part; and 

 therefore, if the angles are rightly assigned, it 

 appears from above, that the bridge ought 

 ultimately to bear 3909 tons. Now the weight 

 of the chain and its appendages is perhaps little 



