Where are the principal tin mines, and of what is this metal composed?
Jonathan Trexlar.
Answer.—Pure tin is an elementary metal, as much so as lead, iron, silver, or gold. The principal tin-producing country is England. The Phœnicians traded with England for tin 1,100 years before the Christian era. There is reason to believe that they got tin from Spain also; but England was depended on for nearly all the tin used in Europe until this ore was discovered in Germany in 1240. It was discovered in Northern Africa, in the Barbary States, in 1640; in India in 1740; in New Spain in 1782. Tin was mined in Mexico before the Spanish conquest, and used in T shaped pieces for money, and in a bronze composition for sharp tools; the principal mines being at Tasco. Peru has valuable mines of this metal, so have New South Wales, Australia, and Banca, and Malacca in the Malay peninsula. Tin has been discovered in Pennsylvania, Missouri, California, and other States of the Union, but not in quantities to tempt capital to engage in mining it. The chief tin-producing countries are the following, arranged in the order of importance: England, about 10,000 tons a year; Malacca, about 8,500 tons; Australia, about 6,000 tons; Banca, about 4,000 tons, and Billiton, about 3,000 tons. Both of these last-named places are islands of the Dutch East Indies.
THE ZERO POINT OF THERMOMETERS.
O’Kane, Neb.
Why was not zero on thermometers placed at the freezing point instead of 32 degrees below?
M.
Answer.—Zero is placed at freezing point on some thermometers, although this is not the case on the Fahrenheit scale, the one in common use in England and the United States. When Fahrenheit graded his thermometer he supposed that there was no greater degree of cold than had been observed in Iceland, or discovered by experimenting with freezing mixtures. This point he marked zero; i. e., empty or nought, as denoting the absence of all heat. It is 32 degrees below freezing, and corresponds to the cold produced by a freezing mixture composed of snow and salt, or sal-ammoniac; from which it has been inferred that this was the test used by Fahrenheit, the instrument-maker of Amsterdam, who introduced this scale into common use, and after whom it is named, but who never actually divulged the secret of his process. It is now known that this is an arbitrary point, far above the lowest temperature in the polar regions and several hundred degrees above the greatest cold produced by artificial methods. In the Reaumer thermometer, generally used in Germany, and the Centigrade thermometer, commonly used in France and by scientists of all nations, zero marks the freezing point of distilled water at the sea level, or under an atmospheric pressure of 14.73 pounds to the square inch. To reduce Fahrenheit to Centigrade, subtract 32 and multiply by 100/180, or 5/9. Conversely, to reduce Centigrade to Fahrenheit, multiply by 9/5 and add 32.