r 59 ] 



X. An Account of the Improvements of the Port of London, 

 a?id more particularly of the intended Bridge, conjijling of 

 a Jingle Arch of 600 Feet Span, 



N. 



OTHING tends fo much to promote the improve- 

 ments of a ftate, as the eftablifhing of an eafy and uninter- 

 rupted communication through all its diftricts. It has there- 

 fore been a leading object with every well-wifher of his 

 country, to render the general intercourse as perfect and con- 

 venient as pofiible. Public roads and bridges have been the 

 means chiefly employed to eftablifh this intercourfe : bridges, 

 as requiring fcientific and mechanical knowledge, and, in 

 many cafes, the utmoft exertions of talents and (kill, have 

 frequently engaged the attention of perfons of eminence and 

 learning. 



It would be an amufing tafk to trace the progrefs of this 

 nfeful art, from the rude efforts of the favage, in his unaudited 

 ■ftate, to the magnificent works of civilized nations, when 

 fcience, wealth, and increafed population, have united ta 

 overcome difficulties confidcred before as unfurmountable. 



When a work is to be performed, mankind, at firft, make ufc 

 of the materials which are nearetl at hand, and which require 

 the leaft (kill in the preparation; timber and (lone were there- 

 fore the materials with which bridges were firft conftructed, 

 and thofe edifices have been rendered more or lefs perfect, in 

 proportion to the quality of the materials, the ftate of the 

 arts, and the degree of wealth and power, in the countries 

 in which they were erected. 



In our oldeft bridges, it is evident, there has been much 

 timidity, and only a fmall portion of (kill : in deep water, the 

 lower parts of the piers have been constructed with timber, 

 and the mafonry begins to take place at the line of low water; 

 the arches are of narrow fpan, and the mafonry employed in 

 them is frequently compofed, partly of rubble, and partly of 

 fquared {tone. In time, means were devifed (by ufing coffer- 

 dams and caiflbons) to place the mafonry as low, commonly 

 lower than the natural bed of the river; the arches were alfo 

 formed of a bolder fpan, and the mafonry was made much 

 more perfect, being all of fquared ftone. In this manner, 

 bridges have been conftructed in Italy, France, and the Britifh. 

 ides, which have juftly been confidered, not only as works 

 of general utility, but of great magnificence. 



In like manner, timber bridges have been gradually im- 

 proved, from the rough trunk of a tree thrown acrofs a fmall 



ftream^ 



