192 VEGETABLE SUBSTANCES. 



making the bridge upon which the spectator stands 

 shake under his feet, as if it were rocked by an 

 earthquake." 



The bridge of Schaffhausen, across the Rhine 

 at the town of Schaffhausen, was one of the 

 most celebrated of wooden bridges ; and the cele- 

 brity was the greater, on account of the architect 

 being an illiterate man, who was not likely to have 

 derived much profit from the works that had been 

 written upon the subject. This architect was Ulric Gru- 

 benman. The construction of the SchafThausen bridge 

 was his first effort; but he was afterwards employed 

 in various other structures of the same description. 

 The width of the Rhine at Schaffhausen is three 

 hundred and sixty-four feet; and the main framing 

 of the bridge was thrown into the form of a single 

 arch, although a pier in the centre of the river 

 divided the water-way into two parts, and also 

 afforded material support to the structure. In this 

 bridge there are regular uprights about seven- 

 teen feet and a half apart, and they were crossed by 

 braces resting on the abutments, and inclining to- 

 wards the centre of the bridge. There were also 

 braces radiating from the central pier, some of them 

 below the roadway, extending to thirty-five feet on 

 each side, and others above. The whole bridge was 

 covered by a ponderous roof. The principal beams 

 in the roadway were joggled throughout the whole 

 length with indentures, like the teeth of two sets of 

 saws, and they were tightened by wedges at each of 

 the cross faces. There were also iron ties from the 

 beam that formed the eaves of the roof, to the prin- 

 cipal beam of the floor, which tended to stiffen the 

 bridge for about a fourth part at each extremity of 

 each of the divisions. Some parts of this bridge 

 were overloaded with timber; but the*whole of it 

 evinced a very considerable and even uncommon 



