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Contributions to Geology and Plant Physiology
Contributions to Geology and Plant Physiology Author:Johns Hopkins University General Books publication date: 2009 Original publication date: 1917 Original Publisher: The Johns Hopkins Press Subjects: Geology Botany Nature / Plants Science / Life Sciences / Botany Science / Earth Sciences / General Science / Earth Sciences / Geology Notes: This is a black and white OCR reprint of the original. It has no... more » illustrations and there may be typos or missing text. When you buy the General Books edition of this book you get free trial access to Million-Books.com where you can select from more than a million books for free. Excerpt: ATMOMETRIC UNITS By Burton E. Livingston The increasing interest in atmometry 1 and the fact that this subject is becoming recognized as of general and fundamental importance in many branches of scientific and practical endeavor, make it desirable that there be some uniformity in our conceptions as to the units employed in atmometric measurements. To approach the subject it is first necessary that the purpose of atmometric observations be clearly in mind; much vagueness still prevails in this connection. The rate of evaporation of water from any surface is dependent on two sets of conditions. One set (internal ones) are effective in or behind the surface and the other (external ones) are effective in front of the surface, that is, in the gas phase of the system. The internal conditions are the characteristics of the evaporating surface and include such features as the concentration of solutes in the liquid water, the influence exerted by the presence of a solid in which the water is imbibed, the shape and extent of the surface, its direction of exposure, its ability to absorb or emit radiant energy, the heat-conducting capacity of the material back of the surface, etc. The external conditions include primarily four characteristics of the space in front of the evaporating surface: the temperature of the gas phase, its moisture condition, the influence of movement or circulation of the gas over the surface, an...« less