SCHUYLKILL PERMANENT BRIDGE. 75 



teports of the '•^Select Committee^'' of the British Parlia- 

 ment, ^^upon the improvement of the Port of London^'* 

 printed in 1801. — The advantages and disadvantages, 

 and the theor\'' and practice of arches, single and multi- 

 plied — the strength, application and quality of materials 

 — the uses and inconveniencies of piers — and all points 

 relating to a project for erecting the single arch before 

 mentioned, over the Thames^ vvill there be found, learn- 

 edly and ably discussed, by men of the first talents, both 

 professional and theoretical, in Great Britain. 



In one of the reports there are two elevations of 

 bridges — one wdth a single arch of iron, 600 feet span^ 

 Calculated for vessels "^0 pass under zY"— the other of 

 a stone bridge, of 9 arches, on piers ^ with an ingenious 

 plan of a draw, designed to exemplify a "mode of ad- 

 mitting ships to pass through it, at all times; without 

 occasioning any interuption to the land communication 

 over it." The relative and positive merits of these and 

 other projects, are elaborately and scientifically discussed 

 and examined, in this, and several precedent reports. 



