Coniributions to Experimental Chemistry. 379 



Nitrate of silver and chloride of gold are very readily reduced 

 by the protoxide of iron, just precipitated from its solution; 

 Thus, a diluted solution of nitrate of silver in ammonia 

 indicates the crystallized protosulphate of iron, if only amount- 

 ing to T(7TFluiy(J of the liquid. 



German Spa^ Brighton, June Ut, 1828. 



Letter from Dr. Nicholas Mill. 

 Sir, Bogota, Colombia, November 23, 1827. 



I TAKE the liberty to forward you, for insertion in the 

 ' Quarterly Journal,' an account of the earthquake which has 

 just desolated this city, and also of a new mineral substance 

 consisting of sulphuric acid and alumine. This mineral salt is 

 unknown, I believe, except as an artificial production ; I shall, 

 therefore, take leave to call it Davite, in honour of Sir Humphry 

 Davy. 1 also send you an analysis of a salt spring in the Andes, 

 containing iodine in the shape of hydriodide of potassium. I 

 have also discovered a new vegetable alkali in the Quina Blanca 

 of Mutis, (Cinchona O valifolia, Cinchona Macrocarpa of Vahl,) 

 which I call Blanquinine, to distinguish it from others, and to 

 convey an idea from whence it proceeds. I am now engaged 

 in examining its salts, the results of which I shall forward you 

 Upon another occasion. 



Earthquake in Colombia, November 16, 1827. 



On the 16th of November, 1827, at a quarter past six o'clock 

 in the evening, the inhabitants of Bogota in Colombia were 

 thrown into the greatest consternation and alarm by the 

 severest shock of an earthquake which has ever been known 

 to visit that city. 



At the moment of its occurrence, a subterraneous noise was 

 very distinctly heard, resembling the noise of a carriage passing 

 briskly over the pavement, and a white thin transparent cloud 

 was seen to hang over the city ; this cloud has been noticed in 

 Italy, as generally, if not always, present near the volcanic 

 commotions of that country, previously, and at the time of 

 these commotions. This cloud is entirely unlike any other 

 which I have ever noticed_, and resembles a thin gauze veil^ 



