FREE BOOKS

Author's List




PREV.   NEXT  
|<   132   133   134   135   136   137   138   139   140   141   142   143   144   145   146   147   148   149   150   151   152   153   154   155   156  
157   158   159   160   161   162   163   164   165   166   167   168   169   170   171   172   173   174   175   176   177   178   179   180   181   >>   >|  
ed with tin ore. The ore got from different mines, he said, differed in quality, as well as in the percentage of tin which it contained. Some had much iron mixed with it, in spite of all the washings it had undergone; some had a little copper and other substances; while some was very pure. By mixing the tin of different mines, better metal could be procured than by simply smelting the produce of each mine separately. Pointing to one of the bins, about three yards square, he told them it contained tin worth 1,000 pounds. There was a large quantity of black sand in one of the bins, which, the agent said, was got by the process of "streaming." It is the richest and best kind of tin ore, and used to be procured in large quantities in Cornwall--especially in ancient times--being found near the surface, but, as a matter of course, not much of that is to be found now, the land having been turned over three times in search of it. This black sand is now imported in large quantities from Singapore. The agent then conducted his visitors to the testing-house, where he showed them the process of testing the various qualities of tin ore offered, to the House for sale. First he weighed out twenty parts of the ore, which, as we have said, resembled snuff. This, he remarked, contained about five-sixths of pure tin, the remaining one-sixth being dross. He mixed it with four parts of fine coal dust, or culm, and added a little borax--these last ingredients being intended to expedite the smelting process. This compound was put into a crucible, and subjected to the intense heat of a small furnace for about twenty minutes. At the end of that time, the agent seized the crucible with a pair of tongs, poured the metal into an iron mould, and threw away the dross. The little mass of tin thus produced was about four inches long, by half an inch broad, and of a dull bluish-grey colour. It was then put into an iron ladle and melted, as one would melt lead when about to cast bullets, but it was particularly noteworthy here, that a very slight heat was required. To extract the metal from the tin ore, a fierce heat, long applied, was necessary, but a slight heat, continued for a few minutes, sufficed to melt the metal. This remelted metal was poured into a stone mould, where it lay like a bright little pool of liquid silver. In a few seconds it solidified, retaining its clear purity in all its parts. "That," said the agent, "is tin
PREV.   NEXT  
|<   132   133   134   135   136   137   138   139   140   141   142   143   144   145   146   147   148   149   150   151   152   153   154   155   156  
157   158   159   160   161   162   163   164   165   166   167   168   169   170   171   172   173   174   175   176   177   178   179   180   181   >>   >|  



Top keywords:
process
 

contained

 

quantities

 

poured

 

slight

 
minutes
 
crucible
 

testing

 
twenty
 

procured


smelting

 

quality

 
percentage
 

inches

 
differed
 

produced

 
compound
 
subjected
 

expedite

 

intended


ingredients

 

intense

 

bluish

 

seized

 

furnace

 

melted

 

bright

 

liquid

 

sufficed

 

remelted


silver

 
purity
 

retaining

 

seconds

 

solidified

 
continued
 

colour

 
bullets
 

extract

 
fierce

applied
 

required

 
noteworthy
 
surface
 

ancient

 

Cornwall

 
mixing
 

matter

 
turned
 

pounds