Scientific Intellir/ence, Sfc, 237 



XVIII. — Emfployment of Iron in Suspension Bridges. 

 By M. E. Martin. 



M. Martin has concluded from his observations that the employ- 

 ment of bars of iron in suspension bridges is more proper than that 

 of wire cables, as being more solid, more durable, and more economi- 

 cal. The experiments of the French marine prove that in relation 

 to resistence to fracture by extension, there are two distinct classes of 

 iron, soft and hard iron. The soft is the only one proper for the 

 manufacture of ship cables. In consequence of its softness it can 

 suffer an elongation of one-fifth of its length before breaking. This 

 quality of iron answers w^ell for suspension bridges. The security of 

 cables would appear to depend upon their property of not breaking 

 until they have suffered great elongation. Hemp cables, from ex- 

 periments made at the hydraulic press of the forge of Guerigny, un- 

 dergo a much less elongation before breaking than chain cables. It 

 appears that iron chain cables are cheaper than wire cables for sus- 

 pension bridges. The greatest objection against the employment of 

 iron is its tendency to oxidation ; but this is remedied, in a great mea- 

 sure, by the mode of suspension, so as that the chains may be placed 

 in a condition to last, in proportion to the other parts. The Langon, 

 on the Garonne, is referred to by Martin as an example of iron last- 

 ing well. — Ann. des Mines y v. 



XIX. — Oil of Canella. 



There are two kinds of this oil, one of which comes to us from 

 China the other from Ceylon ; both are obtained by distilling the 

 bark of canella. The root of canella contains camphor. The 

 Chinese oil possesses a reddish yellow brown colour, and a disagree- 

 able smell. The Ceylon oil has a sweet smell, and is much more 

 valuable, in a commercial point of view, than the other. Dumas 

 and Peligot prepared a pure oil by distilling some good Chinese 

 canella bark after digestion for 12 hours in water saturated with 

 salt. A milky liquid was procured, from which an oil separated. 

 This, when digested with muriate of soda, may be considered as pure. 

 The water, from which the oil is separated in the course of a few 

 hours, contains needle lamellar crystals. 



The oil of canella strongly resembles common camphor, by the 

 action which concentrated nitric acid has upon it, forming a true salt. 

 Muriatic acid gas also combines with it. It combines completely 

 with ammonia, producing a crystalline product. 



Oxygen gas is rapidly absorbed by the oil, giving origin to a new 

 acid, termed cinnamic acid. When the oil is submitted to the 

 action of hot nitric acid, a smell of bitter almonds is disengaged, and 

 benzoic acid formed. When the oil is boiled with a solution of 

 chloride of calcium much benzoic acid or benzoate of lime is formed. 

 Liquid potash has no effect on the oil, but the hydrate, when heated 

 with it, disengages pure hydrogen, and cinnamate of the oil is formed. 

 Chlorine at first forms a substance resembling chloride of heuzoyle, 

 which is gradually transformed into a substance like chloral. 



