BRIDGES. 



681 



A mere plank or tree, when thrown across 

 a stream, assumes a character of gran- 

 deur. It commands respect, from its 

 powers of effecting for man what he could 

 not by any possibility effect for himself. 

 On the other hand, when a trifling stream, 

 or an artificial river, displays a highly 

 architectural bridge of masonry or cast- 

 iron, the effect is offensive, because the 

 means seem out of all proportion to the 

 end. In short, a massive architectural 

 stone bridge, built across a tame piece of 

 water, not, perhaps, more than knee- 

 deep, and an elaborate covered seat of 

 rustic cabinet-work, which cannot endure 

 many seasons, offend precisely for the 

 same reason — viz., the unsuitableness of 

 means to ends." 



Fig. 952 is an iron tension and suspen- 

 sion bridge, also intended for foot-passen- 



Fig. 952. 



gers, but which by an extension in width 

 and strength of material may be adapted 

 for carriages also. For short spaces, the 

 tension bridge, as represented in our 

 woodcut, has all the advantages of the 

 suspension, and is in some situations 

 more suitable. It can be erected at a 

 trifling cost ; that for a bridge for foot- 

 passengers not exceeding 25s. per foot in 

 span — a cost probably below that of any 

 other bridge of equal strength, durability, 

 and elegance of form. 



Rustic bridges are of more humble pre- 

 tensions than those already noticed. 

 They, however, have the merit of being 

 cheap, the material in general being on 

 the proprietor's own property. They also 

 associate well with garden scenery, and 

 admit of great variety of form. We be- 

 lieve that, with one or two exceptions, the 

 designs of the following bridges have not 

 been published. 



Figs. 953, 954, have stone abutments, 

 upon which the principal timbers rest. 

 They are adapted to cross rivulets, or 

 spaces from ten to twenty feet in width. 

 They are best constructed if from three 

 to five feet in width — a breadth quite 



VOL. I. 



sufficient for foot-passengers, for which 

 purpose they are chiefly intended ; but 



Fig. 953. 



they can be so built as to carry carts 

 or carriages, by laying from each abut- 

 ment three 6 -inch Baltic battens, set 

 on edge across, and tied together at the 

 ends and middle with an iron bar, to 

 keep them in their places. Over this a 

 flooring of deal or oak is laid, rough from 

 the saw, the upper surface of which is 

 to be covered with a coat of asphalt, 

 to form the footway, and to keep the 

 flooring dry. The outer sides of the two 

 outer battens are covered with larch 

 bark, and the parapets or hand-rails are 

 constructed of pieces of the same kind of 

 tree, cut into the necessary lengths, and 

 selected so as to be of as near the same 

 thickness as possible. The middle of 

 the footway should be rather higher 

 than the sides, to allow of the escape of 

 rain water, which can easily be done, by 

 laying on the asphalt rather thicker in 

 the middle than at the sides. 



If the span be great, or the contem- 

 plated weights to which it may be sub- 

 jected considerable, struts may be placed 

 in the abutments; and if partially curv- 

 ed, as shown in the figure, the effect will 

 be improved, and considerable strength 

 added to the bridge, by shortening the 

 length, as it were, of the principal beams. 



Fig. 954 is somewhat differently con- 

 structed. A slight curvature is given to 



Fig. 954. 



the principal bearers * and instead of their 

 being covered with boarding, they are 



4 R 



