382 Geolof/ical Society : — 



diffraction, iu which no direct mention is made of the optical 

 phenomena involved. These will be taken up in the second volume. 

 It is not easy, nor is it desirable, for an author of a book on general 

 physics to bring forward many novelties or new modes of treatment. 

 What vve desire in a book of this kind is well digested material, 

 well arranged, and clearly expounded. In these respects Professor 

 Chwolson's Lelirhuch could scarcely be excelled. If the later 

 volumes on electricity and light are as well planned as the present 

 first volume, an admirable text-book on physics, free from the 

 faults which too often mar a mere compendium of scientific know- 

 ledge, will have been given to the world of students. 



XLIX. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from vol. v. p. 17o.] 



January 21st, 1903.— Prof. Charles Lapworth, LL.D., P.P.^., 

 President, iu the Chair. 



''PHE following communications were read : — 

 -■- 1. 'The Figure of the Earth.' By William Johnson Sollas, M.A., 

 D.Sc, LL.D., F.P.S.,F.G.S., Professor of Geology in the University 

 of Oxford. 



The almost precise correspondence of great terrestrial features 

 with a circular form seems to be frequently overlooked. The 

 Aleutian curve has its centre in lafc. 6° N., long. 177° W., that of 

 the East Indies about 15° N. and US'" E., and round the latter 

 centre are several concentric curves. The northern part of South 

 America, the Alpine-Himalayan chain, the western shore of North 

 America, and a portion of Australia, may be similarly reduced 

 to geometric form. A great circle swept through the centres of the 

 East Indian and Aleutian arcs runs symmetrically through the 

 bordering seas of Asia as far as Alaska, borders the inland lakes of 

 America, passes the Californian centre, extends through the middle 

 of the Caribbean Sea, runs parallel with the coast of the Antarctic 

 Continent, and returns to the East Indian centre without touching 

 Australia. This course is in remarkable correspondence with the 

 general trend of the great zone of Pacific weakness. If the pole 

 of this circle in the Libyan Desert is placed towards an observer in 

 a globe, the African Continent appears as a great dome surrounded 

 by seas and separated from the Pacific by an irregular belt of land. 

 A second great circle defined by Lake Baikal, and with its centre at 

 ' the morphological centre of Asia ' of Suess, and passing through 

 the East Indian centre, may be regarded as the direction-circle for 

 the Eurasian folding. These two centres intersect at an angle of 

 39°, and, on bisecting this angle, a mean directive circle is found, 

 with its pole near the sources of the White Kile, 6° north of the 



