Meteorological Perturbations of Sea-Level and Tides.

Perturbatioszs I. 4, or more than 3.4.and 0.56, and a between 0'82 and 0'75.On either hypothesis a* exceeds 8, and the Radau-Darwin approximation is valid.T h e extensive regions of uniform density postulated by Wiechert are theoretically impossible, since both heterogeneity and compressibility would make the density increase towards the centre ; i t might increase discontinuously, but it could not remain constant whcn varies.Thus Wiechert's hypothesis represents an extreme case, in which all the variation of density takes place a t the discontinuities ; Laplace's and Roche's hypotheses make all the variation continuous ; and the actual variation is probably intermediate i n character.The Radan approximation, having been proved valid for the extreme cases, is therefore probably correct for the actual case.Thus a2 must lie between Meteorological Perturbations of Xea-Level and Tides.By A. T.