Proceedings of the Polytechnic Association. 853 



blade of the driver, so that it may be employed by itself as a small 

 and convenient wrench in cases where its use may be applicable. 



The Oak ajs^d its Pkoducts. 



Dr. "W. A. "Weatherbee read a paper on the oak tree and its pro- 

 ducts, and remarked that no variety of wood will last longer than the 

 oak, citing several problematical wooden relics to prove this point, 

 and thus confound the advocates of red cedar, chestnut, and white pine. 

 The paper was succeeded by a discussion which elicited the somewhat 

 well known items of information that an acid may be obtained by the 

 distillation of different kinds of wood, and that the oaks which grow in 

 California are quite different from those found on the Atlantic 

 coast. 



Dr. D. D. Parmelee remarked that wood vinegar is now being made 

 very extensively in this country. 



Dr. P. Yanderweyde said there was a large manufactory in Phila- 

 delphia in which wood vinegar is made. Acetic acid, obtained from 

 the destructive distillation of wood, is diluted, and forms this vinegar. 

 The bichromate of potash is now much used to take out the flavor 

 and burnt taste of the wood vinegar. 



Nitko-Glyceeine. 



Mr. George M. Mowbray, manufacturer of the nitro-glycerine 

 used at the Hoosic tunnel, gave an account of his experiments with 

 that article. JS^itro-glycerine, he said, was first brought into notice 

 as an explosive agent in 1846, on the invention of gun cotton. 

 Nitro-glycerine, as usually made, was constantly giving off a color- 

 less gas in balloon -shaped bubbles ; these bubbles are easily made by 

 agitating the nitro-glycerine in the air. He had exploded the fulmi- 

 nate of silver in nitro-glycerine, and the latter was blown out, but 

 not exploded. Many of the faults attributed to nitro-glycerine are 

 due to its being made impure. As we become better acquainted 

 with this article it will become more safe. Some thirty-five pounds 

 of it are used in the Hoosic tunnel every day. Nitro-glycerine 

 freezes at about forty-eight degrees Fahrenheit ; and in a frozen state 

 he tried to explode it, but failed to do so. In that condition it is next 

 to impossible ; and therefore it is only dangerous in the liquid state. 

 It was also stated that gunpowder and gun cotton might explode in 

 contact with the nitro-glycerine without exploding the latter. 



Dr. Vanderwevde remarked that the chloride of nitrogen is one 



