228 PROFESSOR A. E. H. LOVE ON THE 



northward extension towards Australasia. The contour-line of the continental blocks 

 at mean-sphere-level is a very important and fairly well ascertained datum of the 

 problem. If, however, we attend exclusively to it, we are liable to emphasise unduly 

 those parts of the block which do not rise above the level of the sea. 



56. I calculated the coefficients of a spherical harmonic expansion up to harmonics 

 of the third degree for two different assumptions as to the " value of land." lu the 

 first assumption the value 1 was attached to those points of the surface which are 

 below mean-sphere-level and the value to those points which are above it. In 

 the second assumption the value 1 was attached to those points of the surface which 

 are above sea-level and the value to those below it. The coefficients obtained by 

 the two assumptions were then added. The somewhat greater importance of the 

 mean sphere may perhaps be sufficiently represented by the result that the maxima 

 obtained by using the first set of coefficients are larger than those obtained by using 

 the second set. The combined distribution for the two sets of coefficients is shown in 

 the following table, in which 6 stands for co-latitude measured from the North Pole, 

 and <f) for longitude measured eastwards from the meridian of Greenwich : 



