46 A SYSTEM OF PHYSICAL CHEMISTRY sram-atom. if a monatomic solid be considered, and if the atoms be identified with the resonators.^ Hence, the term 2U reckoned for N " linear " atoms where N is now regarded as the number of atoms in a gram-atom (or molecules in a gram-mole) should be identical with RT, That is, RT = >^NT, or R = /^N. The constant k is therefore simply the gas constant reckoned for a single molecule. We may see in another way that k has this significance. As has ^ been pointed out already, Jeans has shown that for very long waves the law of the partition of energy, or of energy-density between waves of different lengths, as expressed in a formula, must contain the wavelength term to the inverse fourth power. A similar formula was de-
THE QUANTUM THEORY 47 Numerical Values of the Size of the Qua^itum e in different Spectral Regions. In the following table are collected some values of [hv) extending over a wide range. The longest wave measured by Rubens, in 1910, was A = 90/A, though still longer waves have been measured more recently. The shortest wave-length measured is of the order o'lju, or loo/i/x (Schumann). Wave-length A.