The study of environmental biophysics probably began earlier in man's history than that of any other science. The study of organism-environment interaction provided a key to survival and progress. Systematic study of the science and recording of experimental results goes back many hundreds of years. Ben­ jamin Franklin, the early American statesman, inventor, printer, and scientist studied conduction, evaporation, and radiation. One of his observations is as follows: My desk on which I now write, and the lock of my desk, are both exposed to the same temperature of the air, and have therefore the same degree of heat or cold; yet if I lay my hand successively on the wood and on the metal, the latter feels much the coldest, not that it is really so, but being a better conductor, it more readily than the wood takes away and draws into itself the fire that was in my skin. 1 Franklin probably was not the first to discover this principle, and certainly was not the last. Modem researchers rediscover this principle frequently in their own work. It is sometimes surprising how slowly progress is made. Progress in environmental biophysics, since the observa­ tions of Franklin and others, has been mainly in two areas: use of mathematical models to quantify rates of heat and mass transfer and use of the continuity equation that has led to energy budget analyses.

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Microenvironments.- Energy Exchange.- Mass and Momentum Transport.- Applications.- Units.- Transport Laws.- 2 Temperature.- Typical Behavior of Atmospheric and Soil Temperature.- Microenvironment Temperatures.- Soil Temperature.- 3 Environmental Moisture.- Saturation Conditions.- Conditions of Partial Saturation.- Vapor Densities in Nature.- Liquid-phase Water.- Relation of Liquid- to Gas-phase Water.- 4 Wind.- Characteristics of Atmospheric Turbulence.- Flux and Profile Equations.- Fetch and Buoyancy.- Wind within Crop Canopies.- 5 Radiation.- Blackbody Radiation.- Definitions.- Directional Relations.- Attenuation of Radiation.- Radiant Emittance.- Spectral Distribution of Blackbody Radiation.- Spectral Characteristics of Short-wave Radiation.- Radiant Fluxes in Natural Environments.- Estimating Direct and Diffuse Short-wave Irradiance.- Atmospheric Long-wave Radiation.- Radiant Energy Budgets.- 6 Heat, Mass, and Momentum Transfer.- Molecular Diffusion.- Convection.- Resistances to Heat and Mass Transfer in Laminar Forced Convection.- Free Convection.- Combined Forced and Free Convection.- Application in Nature.- Momentum Transport.- 7 Animals and Their Environment.- The Energy Budget Concept.- Specifying Radiant Energy Fluxes for Animals.- Metabolism.- Latent Heat Exchange.- Conduction of Heat in Animal Coats and Tissue.- Application of Energy Budget Equations.- The Climate Space.- The Equivalent Blackbody Temperature.- The Transient State.- Animals and Water.- 8 Humans and Their Environment.- Area, Metabolic Rate, and Evaporation.- Survival in Cold Environments.- Survival in Hot Environments.- Equivalent Wet Blackbody Temperature.- Comfort.- 9 Plant and Their Environment.- Photosynthesis.- Transpiration and the Leaf Energy Budget.- Leaf Temperature.- Optimum Leaf Form.- 10 Exchange Processes in Plant Canopies.- Radiation in Plant Canopies.- Evapotranspiration.- The Energy Budget.- Potential Evapotranspiration.- Non-potential Evapotranspiration.- Appendix: Reconciliation of Terminology.- Table A.3.- Table A.2.- Table A.3.