On the Curve-Of Method.

In the calculation of tile theoretical curve of growth, physical parameters, such as the Doppler velocity, the damping constant, etc., are supposed to be constant for the entire atmosphere. Investigations have therefore been made in this paper to show, in the first place, what is the meaning, if any, of the values determined for such parameters by the curve of growth, when, as a matter of fact, all these parameters vary with depth in real stellar atmospheres; and, second, among many theoretical curves of growth so far computed by various authors, what particular one should be used in order to have the best approximation. For lines formed according to the mechanism of local thermodynamic equilibrium we conclude that the observationally determined value can be regarded as a certain mean value properly weighted according to the formula given by equation (22) in the present paper. And the theoretical curve of growth computed independently by and by Menzel is one of the best for practical use. The temperature, the turbulent velocity, and the damping constant in stellar atmospheres derived from the curve of growth are individually discussed in the light of the present analysis. The observationally determined values for these quantities are, on the whole, consistent with the predicted values as given by the proposed averaging formula.