LKSSUNS IN AHCIIITl-XTUliK. 



313 



control ono of 030 foot ; but tho masonry of tho piers is of tnuoh 

 . proportion than in the ctno of the 

 IJnUnni.i Kn>i;-, \ , \ -. i the forco of the great manses of 

 ioo whii-h in wii. 

 aro brought down 

 th.' sln-uin. 



liritamiiti 



was justly 



. iv.l, at tho 



of its con- 



'.n, a. groat 



mitf tri- 



iiinph ; but, bril- 



liant as was tho 



;i great im- 

 provement has 

 sinuo boon made 

 upon it. This im- 

 provement consists 

 in tho substitution 

 of la / 



for those of a tu- 

 bular form. In tho 

 tubular girders tho 



:ro formed of 

 solid plates. In tho 

 lattice girders, as 

 tho name implies, 

 the sides are com- 

 posed of a kind of 

 open lattice-work 



A good example of the lattice-girder bridge U seen in that of 

 the London, Chatham, and Dover Kailk/uy over the Thames at 

 Blaokf riant, the girders in this ease resting on columns of iron, 



which are set on 

 tone foundations. 

 Railway bridge* 



BRITANNIA TUBULAB BRIDGE ACROSS THE 3IKNAI STRAIT. 



formed of bars 

 or rods of iron, which cross each other diagonally. By this 

 means, in tho first place, a great saving is effected in the 

 material employed j next, every portion of that material can 



tion are 

 all of this fora. 

 Tho riveting is car. 

 ried out on the 

 same principle and 

 to the same extent 

 an in tho case of U,o 

 Britannia Bridge, 

 and the same 

 amount of strength 

 which is there af- 

 forded by the cel- 

 lular arrangement 

 of material above 

 and below, is given 

 in the lattice 

 bridges by iron- 

 beams which, at 

 frequent intervals, 

 cross tho principal 

 girders, both at 

 top and bottom, at 

 right angles. 



Tho use of iron 

 girders has greatly 



facilitated the construction of what are known as skew bridges, 

 i.e., bridges tho lino of which ruiia askew or obliquely to 

 that of tho stream. The peculiar formation which, it was 



BKIDOE ACROSS T11K NIA'.i.\i:v UIVER, BKI.'UV !K 



be so adjusted as to bear a full share of the strain of the 

 traffic ; and lastly, the whole fabric presents a smaller surface 

 to the action of the wind and weather, while at the same time it 

 can be more easily repainted or repaired. 



necessary to give to tho component parts of the arches in 

 stone bridges, on the skew principle, rendered these difficult 

 of construction, and they were comparatively unsafe for the 

 enormous strain of general railway traffic. 



