1813.] Royal Society. JCI 



general, the glass was broken by an explosion ; and when that 

 did not happen, the proportion of chlorine and azote evolved 

 could not be determined, on account of the unknown proportion 

 of atmospheric air that remained in the vessel. When the 

 detonating compound is brought in contact with mercury, a 

 white powder is formed, and azotic gas disengaged. In one 

 experiment a detonation took place, which obliged him to work 

 upon smaller quantities. The white powder was found to be a 

 mixture of calomel and corrosive sublimate; and it sublimed 

 entirely without the disengagement of any gas, indicating the 

 absence both of hydrogen and oxygen. Muriatic acid does not 

 destroy the colour of solution of indigo in sulphuric acid; but 

 if it be impregnated with chlorine, it destroys a determinate 

 quantity of the blue colour, according to the proportion of chlo- 

 rine present. The same thing happens when the detonating 

 compound is dissolved in muriatic acid. This furnished a method 

 for determining the proportion of chlorine contained in the deto- 

 nating compound. The result of all these methods of analysis 

 is, that the detonating compound is composed of 



Chlorine 91 



Azote 9 



100 



reckoning by weight, or if we reckon by bulks of 



Chlorine 400 



Azotic gas 1 00 



500 



>>ir H. Davy proposes to call this detonating compound 

 irotaiie. 



At the same meeting were read some observations on a new 

 comet, observed by Capt. Hill, in the Hon. East India Com- 

 pany's service. 



On Thursday, the 8th of July, the following papers were read: 



1. A catalogue of the positions of a number of circumpolar 

 stars by the Astronomer Royal, Mr. Pond. 



2. An analysis of a substance thrown out of Mount Vesuvius, 

 by James Smithson, Esq. This substance had been sent to Mr. 

 Smithson when in Italy in 1 /94, in order to determine its 

 nature; and he ascertained, by a number of trials, that it con- 

 sisted chiefly of sulphate of potash. This result was published soon 

 after in an Italian Journal, but no subsequent notice was taken of 

 it by mineralogists. Mr. Smithson was induced to examine it 

 with more accuracy lately, and the result of his experiments is, 

 that it consists of sulphate of potash, sulphate of soda, sulphate of 

 ammonia, muriate of ammonia, muriate of copper, and muriate 



