1890.] NEW YORK ACADEMY OF SCIENCES. 43. 



moved, and large tracts given over to the cultivation of corn, 

 grain, etc. This was the Mound Age, and these constructions 

 were certainly abandoned over one thousand years since. The 

 Pueblo Indians now existing in Arizona and New Mexico took 

 their origin from Central America and spread as far north as 

 Salt Lake, Utah, and south as far as Chili. Their structures 

 were permanent stone buildings, many of which still exist in a 

 good state of preservation. 



Prof. Munroe found rocks on the Ohio River, near the Penn- 

 sylvania line, inscribed with figures of men, horses, and other 

 animals. At low water these figures can be distinctly observed. 



Dr. Nkwberry announced that the next meeting of the Geo- 

 logical Congress would be held in Washington, D. C, August 

 26th, 1891 ; that of the American Association for the Advance- 

 ment of Science at the same place August 19th, 1891. 



Dr. H. C. Bolton spoke briefly on the remarkable addition to 

 chemical knowledge recently made by Prof. Th. Curtius, of 

 Kiel, viz., a new strong acid called in German " Stickstoffwasser- 

 stoifsaure" — in English hydrazoic acid — having the formula 



N 

 HN3; or, H-N( II 



^N 



Curtius obtained it in several ways, the most convenient meth- 

 od being by converting hippurylhydrazin into nitrosohippuryl- 

 hydrazin, and decomposing the latter with alkali. 



NO 



/ /N 



C,H,CONHCH,CO. N =C,H,CONHCH,COOH + HN || 



Nitrosohippurylhydrazin, \ Ilippuric acid. \N 



NH, 



Hydrazoic 

 acid. 



The new acid is a gas, having a frightful suffocating odor, ir- 

 ritating the mucous membrane and producing headache. It is 

 very soluble in water, yielding a strong acid solution, like hy- 

 drochloric acid. This solution dissolves iron, zinc, copper, alu- 

 minium, and magnesium, with liberation of hydrogen and forma- 

 tion of nitrides of the metals. With salts of silver and mercury 

 white precipitates are formed resembling chlorides of these 



