44 TRANSACTIONS OF THE [NOV. 24, 



metals, but the silver compound is not blackened by light ; the 

 mercurous, copper, and ferrous salts are explosive. 



Advantage is taken of the insoluble silver salt to prepare the 

 acid in a pure state ; boiled with dilute sulphuric acid it yields 

 hydrazoic acid. An aqueous solution containing 27 per cent of 

 the gas is much heavier than water and sinks to the bottom of 

 the vessel into which it is poured. The solution yields white 

 clouds with ammonia, just like hydrochloric acid. Prof. Cur- 

 tius plans to build up an entire new series of nitrogen compounds 

 of greatest interest to the chemical world. 



Dr. Bolton spoke of the great importance of the discovery of 

 the new strong acid from industrial, analytical, and physiological 

 points of view. 



November 24th, 1890. 



Stated Meeting. 



The President, Dr. Newberry, in the chair. 



About two hundred persons present. 



The minutes of November 17th were read and approved. 



Dr. Bolton announced that a joint meeting of the Academy 

 and the American Folk-lore Society would be held at Columbia 

 College, Friday evening, November 28th, at 8 o'clock. 



President Newberry announced the opening of the Pablic 

 Lecture Course of 1890-1891, and introduced Mr. Frederick H. 

 Chapin, of Hartford, Conn., who spoke on the 



CLIFF DWELLINGS OF THE MANGOS CANONS. 



The lecture was highly novel and interesting, and was illus- 

 trated by a large number of lantern views taken by the lecturer. 



At the close of the entertainment a vote of thanks was unani- 

 mously given Mr. Chapin. 



