Abstract
The fundamental normal mode of the free oscillation of water in a lake of elliptic boundary with small eccentricity and of uniform depth is investigated by means of a kind of boundary perturbation method. An approximate formula for the relationship between the frequency of the fundamental normal mode of oscillation and the eccentricity of the elliptic boundary of the lake is derived correct to the sixth power of the latter, which may be adequately used in case when the eccentricity is not so large.
