PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 457 



ing thousands of pounds are found scattered over the country, and 

 several thousand specimens have been enumerated. 



The nitrate of soda was of great importance to us during our 

 war. It enabled us to use all our saltpetre for the manufacture 

 of gunpowder, as it supplied the demand for nitric acid, and thus 

 released nitrate of potash from various other uses w'here it was 

 formerly considered indispensable. The soda salt cannot be used 

 for gunpowder as it absorbs moisture, but in other respects it 

 can be substituted for nitre, especially in the preparation of nitric 

 acid. The origin of the deposit is supposed to be the same as 

 that of the beds of guano. Large accumulations of decaying 

 organic matter have furnished the nitrogen, and alkaline lakes have 

 provided the soda. It is to be hoped that the beds will not soon 

 be exhausted, as the article is of great importance in the arts. 



Indium. 



Professors Eeich and Richter published a preliminary notice of 

 this metal in Erdmanii's Journal, September 1st, 1863. 



F, Reich is Professor of Physics at the School of Mines, Frei- 

 berg, Saxony. He is about seventy years of age, and is well 

 known for his important investigations upon the density of the 

 earth. He no longer delivers lectures but directs the practical 

 operations of the laboratory. 



Th. Richter is about thirty years of age, and was assistant to 

 Professor Reich in the laboratory. He gives instruction in the 

 blow-pipe, and has edited the work of the late Professor Plattner 

 on metallurgy. He is a great favorite of the pupils of the School 

 of Mines, and is destined, if he lives, to become one of the most 

 prominent professors of the ancient school of Freiberg. 



In consequence of the fact that thallium had been detected in 

 a number of furnace products, it occurred to the professors to 

 examine some impure chloride of zinc which they had obtained 

 by distilling an ore which contained arsenic, sulphur, iron, zinc, 

 manganesg, copper, tin, and cadmium. To their surprise there 

 was no green line of thallium, but two blue lines made their 

 appearance on a different part of the spectrum. They immedi- 

 aitely set to work to isolate the unknown body, and were soon 

 successful. They proposed the name of indium from the color 

 of the lines which lead to its detection. At tbis early stage all 

 that they could say of it was that sulpberetted hydrogen did not 

 precipitate it from acid solutions of the chloride; that ammonia 



