154 JV>7/' Method of constructing wooden Bridges, 



periodical works, not to be hasty to commit themselves in 

 questions of science, on the authority of reports drawn up 

 by jealous rivals for national fame. We could name a 

 most respectable journal which has fallen into this blunder. 

 As to some more obscure writcrs/who have ventured to talk 

 about " the pretended discovery of the decomposition of 

 the alkalies," they will probably show a little more modesty 

 in their remarks in future. 



XXVIII. Intelligence mid Miscellaneous Articles. 



jVI. Wikbkking, director of roads and bridges to the 

 king of Bavaria, has discovered a method of constructing 

 wooden bridges, which in point of strength and solidity 

 promise a duration of several centuries. They are also re- 

 markable for the elegance of their form and the width of 

 the arches. A bridge has been constructed on the above 

 plan over the river Roth, five leagues from Passau, consist- 

 ing of a single arch two hundred feet wide: another 

 has been made for a large city, two hundred and eighty six 

 feet wide. These arches mav be so constructed as to ad- 

 mit of ships of war or merchant vessels passing through 

 them, an aperture being made in the centre, which can be 

 opened and shut at pleasure. Another advantage possessed 

 by these bridges is that of being speedily taken to pieces : 

 if it be necessary to stop the progress of an enemy, the 

 arch may be removed in one day, and th2 abutments in 

 another, without cutting the smallest piece of timber. 



With respect to the advantages in point of ceconomy 

 resuliing from the adoption of M. Wiebeking's plan ; it has 

 been estimated that a stone bridge of similar dimensions to 

 a wooden one of a given size would cost two millions of 

 florins, whereas the latter would cost only 50,000 florins ; 

 and on the supposition that a wooden bridge will only last 

 100 years, it follows that, taking the interest on the prin- 

 cipal sum into the computation, there will result a sav- 

 ing of eleven millions six hundred and eighty thousand 

 florins. 



The Pharmaceutical Society of Paris has announced the 

 following as prize questions for the present year : 



1. Ascertain as far as possible, whether there exists in 

 vegetables an identical principle which chemists have de- 

 signated by the name of extractive? — Ought we to retain 



the 



