SCHUYLKILL PERMANENT BRIDGE. 70 



We therefore found ourselves compelled to progress, on the 

 plan we have been executing ; let the expence or difEcultv be 

 never so discouragmg. Happily we have thus far succeeded ; 

 but it is with some emotion, v/e look back at the dangers we 

 have escaped." 



By a report of December 26th 1 803, it appears that (although 

 the work was not then finished,) " The whole of the stone 

 work from its commencement consisted of 105,780 feet of cut 

 and hammered stone, included in 15,131 perches of masonry. 

 When it is considered that one half, at least, of this rvas erec- 

 ted under -water, it is not extraordinary that the work should 

 have been tedious, difficult and expensive." 



The cut stone Avas very expensive ; though an expedient of 

 putting the faces of those under xvater only at the joints, about 

 two inches broad, was suggested to, and adopted by the mason. 



The eastern pier is 40 feet high from the foundation, and 

 contains 3635 perches of masonry. 



The western pier is 55 feet 9 inches high from the foun^ 

 dation, and contains 6178 perches of masonry'. 



Seeing, then, that such difficulties and unavoidable 

 expenditures attend bridges erected on piers, especially 

 xvhere batterdeaus, or coffer dams are used, it is to be re- 

 gi'etted that the genius of hydraulic engineers and archi- 

 tects, or others, whose minds have been occupied in such 

 subjects, has not, in a long course of time both enlight- 

 ened and active, produced some practical specimens of 

 single arches, of such span as to supersede the use of 

 piers \ in deep and navigable streams, at least. This 

 not having been done, sufficiently proves, that (however 

 plausible the theory) the practice has not, though indu- 

 bitably desirable, been thought safe or justifiable. There 

 have been sundry plans proposed; but none accom- 



K 



