404 MENAI BRIDGE. 



in this bridge. For considering it as a common 

 catenary, with this span and versed sine, the 

 incHnation of the top hnk to the horizon would 

 be about 16**. 49'; and as the strain on the 

 links is as the secant of their inclination, the 

 strength of the top and bottom links ought to 

 be as 10447 to 10000. This difference is 

 usually neglected: whether it has been paid 

 any attention to in this much more perfect struc- 

 ture, I have not particularly noticed. 



ADDITIONS. 



The effect on the equilibrium of the bridge 

 from expansion and contraction is but small. 

 I was informed by an intelligent person who 

 resided near to it, and had paid particular 

 attention to it, at different times of the year, 

 that the center of the suspended part rises 

 from contraction about 11 inches higher in 

 winter than in summer; and that the saddles 

 on the pillars recede, each about 1| inches, 

 both together 3 inches, from each other through 

 that cause. 



In this sti'ucture, the versed sine, though 

 larger than was at first contemplated, is less 



