First principles of chemistry for the use of colleges and schools / by Benjamin Silliman.

  • Silliman, Benjamin, 1816-1885.
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: First principles of chemistry for the use of colleges and schools / by Benjamin Silliman. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    part of his body, beneath his feet as well as on his head; and in the inner cavities as well as on the outer surface. 32. Limits of the Atmosphere.—A person who has risen in a balloon, or on a mountain, to the height of 2*705 miles, or 14,282 feet, has passed through one-half of the entire weight of the air, and finds his barometer to indicate this by standing at 15 inches. The air grows more and more rare as we ascend, and tho barometer falls in exact proportion. The inconvenience which travellers have experienced in ascending high moun- tains has, it is said on good authority, been very much ex- aggerated. The heart continues its action under a diminished external pressure, and no serious consequences, it is believed, ever follow, as the bursting of bloodvessels or lesion of the lungs, as some have asserted. On the summit of Chimbo- razo, Baron von Humboldt found that his barometer had sunk to 13 inches 11 lines; and the same philosopher de- scended into the sea in a diving-bell until the mercurial co- lumn rose to 45 inches : he consequently has safely expe- rienced a change of 31 inches of pressure in his own person. The upper limits of the atmosphere cannot be determined very accurately ; but, from the refraction of light as observed in the rising and setting of stars, astronomers have inferred that it is probably about forty-five miles high. Weight and Specific Gravity. 33. Weight is the measure of the force of gravity, and is directly proportional to the quantity of matter in a given space. Weight is determined by the balance, an instru- ment to which the chemist appeals at every step of his in- vestigations. Modern instruments enable us to determine this element of accurate science, to the greatest nicety. The specific gravity of a body is its weight as compared with an equal bulk of some other substance assumed as the unit of comparison. A cubic inch of gold is more than 19 times as heavy as a cubic inch of ice or of water: hence the gold is said to have a specific gravity of 19, compared with water. Pure water has been adopted as the standard of compari- 32. What is the height of the atmosphere? 33. What is weight? What is specific gravity ? What is the standard of specific gravity ?