302 Mr Sang on the Construction of Oblique Arches. 



diately chalked out. One miglit almost imagine that a mono- 

 mania had seized us, and that the tulip, the dog, the pigeon, 

 and all the other fanciers had deserted their peculiar depart- 

 ments to concentrate their energies on this one grand matter 

 of roads. The madness is a very reasonable one ; for if there 

 be a hill, multitudes daily climb and descend it ; or if a road 

 be circuitous, the quantity of unnecessary travelling might 

 soon be sufficient to carry one comfortably round tho globe. 



While journeying, we are often annoyed by bridges. Some- 

 times, for cheapness, they have been erected far out of the 

 luae of road, and we enjoy on one side of a river the dehghtful 

 prospect of doubling along the other. At other times, after 

 skirting the banks as if on a journey to the source, we are all 

 at once wheeled right across the water, and ere we are certain 

 that our necks are yet safe, an equally sudden turn restores 

 us to our original direction. And occasionally our vexation 

 is crowned by an altercation between the drivers as to which 

 of tAvo vehicles is bound to back down the steep slope of some 

 antiquated erection. That time has now gone bye when a 

 bridge of any kind was hailed with satisfaction ; we have 

 scarcely such a thing as a ford wherewith to contrast it, and 

 having only bridges to compare with bridges, we have become 

 somewhat nice in our taste. Many of the old high-backed 

 bridges have been replaced by othei's with level road-ways ; 

 these again by bridges with road-ways inclined to suit the 

 elevation of the opposite banks, and now another improvement 

 is beginning to be called for, that of crossing the river 

 obhquely, so as to make the bridge harmonize with the gene- 

 ral line. This we may consider as the ne plus ultra in bridge 

 building, for then the road-way over the bridge coincides both 

 in plan and in section with the rest of the road, and therefore 

 conducts us in the easiest manner possible from the one bank 

 to the other. The skewed arch is inseparable from the rail- 

 way, as by its introduction alone the engineer is able to free 

 the line from awkward and injui'ious turnings. 



Having been consulted concerning the construction of an 

 oblique bridge of considerable magnitude, and never having 

 met with any regular investigation into the theory of such 

 structures, I was induced to undertake the analysis. The 



