The American Educator; Completely Remodeled and Rewritten from Original Text of the New Practical Reference Library, with New Plans and Additional Material Volume 6

The American Educator; Completely Remodeled and Rewritten from Original Text of the New Practical Reference Library, with New Plans and Additional Material Volume 6

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1922 edition. Excerpt: ...to the air at common temperatures, it undergoes slow combustion, emits a white vapor of a peculiar odor, appears luminous in the dark and is gradually consumed. On this account phosphorus should always be kept under water when it is desirable to preserve it. A very slight degree of heat is sufficient to inflame phosphorus in the open air. Gentle pressure between the fingers, friction, or a temperature not much above its point of fusion, kindles it readily. Phosphorus is very poisonous. Burns from it are difficult to heal, and a small quantity taken into the system causes death. It should not be handled except under water. Phosphorus was formerly extensively used in the manufacture of matches, but its use is now forbidden by law in most countries because of the disease known as phossy jaw, caused by it. Its compounds known as phosphates are used in medicine, and phosphate rock is extensively used as a fertilizer, since phosphorus is an important plant food. It is also an important animal food, and is found in bones and in the brain and nerves in larger proportions than in other tissues. PHOTO-ENGRA'VTNG, a process of engraving, by which the picture is first transferred to the block or plate by means of photography. The result is a printed surface, corresponding to the original from which the photographic image was taken. For a description of the different phases of the process, see Electrotyping; Halftone; Lithography) subhead PhotoLithography; Photogravure; Zinc Etching. PHOTOGRAPHIC SURVEYING, a form of surveying which originated with the French and adopted to a limited extent in America, particularly in the prairie provinces of Canada. The camera is provided with cross wires and a leveling apparatus. In surveying, two stations (or more)...show more

Product details

  • Paperback | 350 pages
  • 189 x 246 x 19mm | 626g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236927257
  • 9781236927255