A Short Account of Experiments and Instruments: Depending on the Relations of Air to Heat and Moisture

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William Blackwood, and J. Ballantyne & Company; and for Longman, Hurst, Rees, Orme, & Brown; and John Murray, London, 1813 - Heat - 178 pages

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Page 31 - The quantity of evaporation from a wet ball is mésame as from a circle having twice the diameter of the sphere. In the atmometer, the humidity transudes through the porous substance, just as fast as it evaporates from the external surface ; and this waste is measured by the corresponding descent of water in the stem.
Page 53 - This heat will continue to accumulate, till its farther increase comes to be counterbalanced by an opposite dispersion, caused by the rise of temperature which the ball has come to acquire. At the point of equilibrium, therefore, the constant accessions of heat derived from the action of the incident light, are exactly equalled by the corresponding portions of it again abstracted in the subsequent process of cooling. But, in still air, the rate of. cooling is, •within moderate limits, proportioned...
Page 123 - ... the 80th part; at that of 86°, the 40th part; at 113°, the 20th part ; and at that of 140°, the 10th part ; so that the air has its dryness doubled at each rise of temperature, answering to 27° of Fahrenheit. While the temperature, therefore, advances uniformly in arithmetical progression, the dissolving power, which this communicates to the air, mounts with the accelerating rapidity of a geometrical series.
Page 13 - IS shades of Autumn ; and it enables us to compare, with numerical accuracy, the brightness of different countries, — the brilliant sky of Italy for instance, with the murky atmosphere of Holland.
Page 55 - ... her sober mantle ; it marks the growth of light from the winter solstice to the height of summer, and its subsequent decay through the dusky shades of autumn...
Page 32 - The mean quantity held in solution in a cubic foot of air, is 3.789 gr. The rate of exhalation from the surface of the ground is scarcely of less consequence than the fall of rain, and a knowledge of it might often direct the most important operations. Mr. Leslie invented an instrument for measuring the quantity of moisture exhaled from a humid surface in a given time. This he called the Atmometer, and he has estimated that the daily exhalation from a sheltered surface of water would, at the mean...
Page 130 - ... parts ; the difference, or 8.6 parts, forms the measure of precipitation, corresponding to the 2325th of the whole weight of the commixed air. It would thus require a column of air 30 miles in length to furnish, over a given spot, and in the space of an hour, a deposit of moisture equal to the height of an inch. If the sum of the opposite velocities amounted to 60 miles an hour, and the intermingling influence extended but to a quarter of an inch at the grazing surfaces, there would still, on...
Page 139 - Nay, a far less tenuity of the medium, when combined with the action of sulphuric acid, is capable of producing and supporting a very intense cold. If the air be rarefied only 50 times, a depression of temperature will be produced, amounting to 80 or even 100 degrees of Fahrenheit's scale.
Page 81 - ... bearing divisions, each of them corresponding to an internal annular section, equal to a film of liquid that would cover the outer surface of the ball to the thickness of the thousandth part of an inch.
Page 142 - ... will shoot beautifully through the liquid mass, and entwine it with a reticulated contexture. As the process of congelation goes forward, a new discharge of air from the substance of the water takes place, and marks the regular advances of consolidation. But after the water has all become solid ice, which, unless it exceed the depth of an inch, may generally be effected in less than half an hour, the circle of evaporation and subsequent absorption is still maintained. A minute film of ice, abstracting...

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