370 THE EOYAL INSTITUTION. [CHAP. VI. 



The battery consisted of forty double plates, thus 

 arranged : Each trough, excepting the end ones, was 

 separately connected with a glassful of mercury by 

 polished copper wire, and each pair of glasses was 

 connected by very fine polished iron wire. 



The effects took place at the moment of contact 

 at all the wires, so that there could have been no 

 neutral point. 



For the last time, after innumerable failures, he re- 

 turned to the decomposition of nitrogen. 



On August 13 'experiment very cautiously made of 

 the action of potassium on nitrogene. Light green 

 when mercury is employed, red when potassium.' 



On October 23 the Laboratory Book says: 



e A series of experiments to attempt to decompose 

 hydrofluoric acid, and to ascertain the constitution of 

 the fluoric combinations. 



6 1. To obtain pure hydrofluoric acid. 



< 2. To obtain silicofluoric acid gas, and to decompose 

 it by potassium and by potash, and to ascertain the 

 quantity of fluate of lime they will give. 



c 3. To make pure prussic acid. 



c 4. To act upon pure prussic acid by chlorine.' 



On November 5 a new detonating compound was 

 formed ; this was the chloride of nitrogen. 



This year Davy gave his last course of lectures on 

 Chemical Philosophy at the Eoyal Institution. 



An account of four of these lectures c was taken off 

 from notes by Mr. Faraday.' The subjects were 

 Eadiant Matter, Chlorine, Simple Inflammables, and 

 Metals. After the report of each lecture he gave the 



