PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 537 



sun's rays for several hours becomes of a bluish green, and at night is 

 again colorless. He supposes an atom of oxygen leaves the molybdic acid 

 and forms oxygenated water, which is again freed at night and passes to 

 the acid; and he proposes to use this substance for the purpose of measuring 

 the force of the actinic rays. This substance is not as sensitive as several 

 others, and a method of using it expeditiously is not so easily devised as 

 the doctor supposes. 



Anesthetic. 



The Nitrate of amyle, according to Dr. B. W. Richardson, when inhaled, 

 acts more powerfully than an}'' other known agent in increasing the action 

 of the heart. Its cflect upon the lower animals is remarkable; in frogs 

 animation could be suspended for nine days, with perfect after-recovery. 



Reciprocal Action between Plants and Gases. 



The question how plants are affected by the contaminations of the at- 

 mosphere, is becoming a serious one in some of the manufacturing dis- 

 tricts of Great Britain. In the coal and mining localities the air is tainted 

 chiefly with sulphurous and hydrochloric acids and ammonia. According 

 to the experiments of Mr. R. Garner, reported to the British Association, on 

 plants by means of gases applied to both the leaves and roots, it appears 

 that annuals suffer less than evergreens. Some plants which luxuriate on 

 the coal strata, such as the oak, the holly, and some ferns, died soon after 

 the mines began to be worked. It was fortunate, however, for the agri- 

 culturist, that wheat and corn flourish, when nothing else could, in such 

 districts. 



Aluminium Bronze. 



The manufacture of this alloy, having the beauty of gold and the strength 

 of iron, has become of great importance. The French now obtain the alu- 

 mina from a mineral called bauxite, containing 51 per cent, of alumina, 25 

 of oxide of iron, a small portion of titanium and silica, a trace of carbon- 

 ate of lime, and 11 per cent of water. 



Preservation of Stone. 



M. Kuhlman has continued his researches on the preservation of mate- 

 rials for building and ornamentaticm, and has presented to the French 

 Academy an account of his experiments on the action of different gases on 

 colored stcjnes, at elevated temperatures, but not so high as to effect any 

 decomposition of the materials. The stones were exposed to a current of 

 gas in a porcelain tube. Tlie fjllowing results were obtained : 



Oxygen decolorized marbles colored with bituminous matters. Agates 

 and grt-eu aud yellow jasper turned brown or bright red. Smoky quartz, 

 amethyst and topaz were decolorized, but preserved their transparency. 

 Emeralds and sapphires turned pale; caruelians were decolorized and 

 slightly decomposed; binoxide of nitrogen and chlorine behaved nearly 

 the same as oxygen. 



Hildrogen turned all the stones colored with metallic compounds black 

 by reducing the metals. Ammonia ,x\&o reduced the metals. Cyanogen acted 

 energetically as a deoxidizer. 



Bulpkuretted Hydrogen did not affect colored diamonds and sapphires, but 



