Scientific American; Supplement Volume . 70

Scientific American; Supplement Volume . 70

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1910 edition. Excerpt: which pressure can be reckoned--first, that which includes the pressure exercised by the atmosphere, this is called "absolute pressure"; and secondly, that which does not take the pressure of the atmosphere into account; the latter is that generally shown by gages, and is usually talked of as "pressure." If now the pint measure be closed at the top, and another pint of air be forced into it, there will be a double quantity of air in the measure trying to force its way out in all directions; the original pressure will therefore be doubled, and there will be an absolute pressure of 30 pounds on the square inch inside the measure on the top, bottom, and sides; but, of course, only 15 pounds "pressure" above that of the atmosphere inside the measure. The same result could have been obtained if an India-rubber ball containing a quart of air had been pressed on from the outside, and the ball squeezed in until its capacity had been reduced to one pint. A quart of air (that is, two pints of air) would then be held in one pint of space, and the pressure inside it therefore doubled. It is convenient to use the word "volume" to express the quantity of air in any receptacle at atmospheric pressure. The following simple rule can, therefore, be used, viz.: If one volume of air is present in a receptacle, the pressure is atmospheric pressure, or 15 pounds absolute pressure. If above atmospheric pressure Is required, we have merely to divide 90 by 15 to see how many volumes of air, in addition to the one already present due to the atmosphere, must be forced in. In this case six more volumes will produce a pressure of 90 pounds on the square inch above atmospheric pressure. These facts constitute what is more

Product details

  • Paperback | 706 pages
  • 189 x 246 x 36mm | 1,238g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236554787
  • 9781236554789