1887.] NEW TOEK ACADEMY OF SCIENCES. 157 



and finished in 1732, consists of thirty-five arches of various di- 

 mensions, the largest having a span of 108 feet. 



The bridge of Neuilly, which crosses the Seine, built between 

 the years 1768 and 1780 by the famous Perronet, is considered 

 one of the most beautiful of existing bridges. It consists of five 

 equal arches of 128 feet span each, each arch being composed of 

 eleven arcs of circles of different diameters, the resulting effect 

 being a curve in appearance like an ellipse, but even more pleas- 

 ing to the eye than an ellipse. 



In England the oldest bridge remaining entire is the bridge of 

 Croyland, in Lincolnshire. It was erected about the year 860. 



The first bridge over the Thames was of wood, built ia the 

 reign of Ethelred II., about the year 1000. 



The Old London Bridge was begun in 1176, under Henry II., 

 and finished in 1209. The length was 940 feet, the height 44 

 feet, and the width between the parapets 47 feet. It was hardly 

 much more than a wall of stone thrown across the river, a few 

 openings being left for the passage of the waters of the Thames, 

 half the water-way being taken up by the piers. It was exten- 

 sively repaired and altered five hundred years after its erection, 

 and in 1823, the obstruction which it offered to traffic on the 

 river having become the subject of persistent and loud com- 

 plaints, this bridge was removed and the New London Bridge 

 erected in its place by Mr. John Rennie. The new bridge was 

 placed near the site of the old bridge, and is formed of five semi- 

 elliptical arches, the least of which is larger than any elliptical 

 arch ever before erected . 



The Westminster Bridge over the Thames was constructed by 

 a Swiss Engineer, Mr. Labalye. It is 1,220 feet long, and con- 

 sists of thirteen large and two small arches. It was opened to the 

 public in 1750. 



Blackfriars Bridge, also one of the London bridges, was built 

 by Mr. L. Mylne, between the years 1760 and 1771. It is 999 

 feet long and consists of nine elliptical arches. 



The Waterloo Bridge across the Thames, nearly midway be- 

 tween the Westminster and the Blackfriars bridges, is, perhaps, 

 the most magnificent structure of its kind in Europe. It was 



