Radiation Temperature: Dew

THE letter in NATURE of October 23 on radiation temperature from Mr. Spencer Pickering reminds me that the theory of the equilibrium temperature is given by Clerk Maxwell in his little-known article on Diffusion (“Ency. Brit.,” ninth edition, p. 218). Maxwell shows that in still-air temperature θ 0 a thermometer will gain heat per sec. 4πCK(θ 0 θ 1 ), where C is the electrical capacity of the bulb, K the conductivity constant for air; and that it will give up heat per sec. AR(θ 1 θ), where A is the area of the bulb, R the radiation constant, and θ the temperature towards which radiation occurs. If the bulb be spherical C = r , its radius. Consequently,