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LXII. On the Construction of Skew Arches. By 
Cuartes Fox, Esq.* 
[With a Plate. ] 
atid bridges have hitherto been comparatively little used ; 
but since railways have been introduced, in which it is 
highly important to preserve as direct and straight a line as 
possible, they are very frequently required, as a railway 
passes through the various districts without the possibility of 
regarding the angle at which it may cross canals and roads, 
its course being in great measure controlled by the naturai 
features of the country. 
Wherever a canal is thus crossed at an angle, we must 
either divert the canal, so as to bring it at right angles to the 
railway; or we must build a common square bridge of suffi- 
cient span to allow the canal, its course being unaltered, to pass 
uninterruptedly under it; or we must erect a proper skew _ 
bridge. The first of these is often impracticable, as provisions 
are generally inserted in the Acts of Parliament, for preserving 
the canal from any alteration in its course; and even if this 
were not the case, the diversion of a canal causes great expense, 
and is attended with much inconvenience to its traffic: the se- 
cond is a most unscientific mode of overcoming the difficulty, 
and would also involve very serious expense, arising from the 
necessity of making use of an arch of much larger dimensions 
than would be required were the proper oblique arch erected 
initsstead. By referring to Plate III. figs. 1 and 2, this will be 
apparent: for this diagram I have selected the angle at which 
the London and Birmingham railway crosses the Grand Junc- 
tion Canal, being an angle of 30 degrees. It is for the above 
reasons that oblique arches are now so frequently erected; and 
a good method of building them is, therefore, of considerable 
importance. 
As many practical men with whom I am acquainted have 
experienced considerable difficulty in the construction of 
skew bridges, I was led to turn my attention to the subject ; 
and haye at length succeeded in rendering the principles of 
it easy to be understood. 
All persons are acquainted with the manner in which com- 
mon square arches are built, where all the courses are square 
to the face, and parallel both to the direction and surface of 
the road or river running under it, by which means the thrust 
or strain is always at right angles to the joints or beds of the 
* Communicated by the Author. 
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