THE sudden movement that causes a great earthquake must alter the conditions of strain in the surrounding crust. The strain may be increased in some regions and decreased in others and the changes may be great enough to precipitate or prevent the occurrence of what Mr. Oldham has called “sympathetic earthquakes”. It thus becomes of some interest to ascertain how far the influence of a great earthquake may extend from its source, and the present brief note is an attempt to examine this point in the case of one well-known and well-studied earthquake, that of Mino-Owari in Japan on 28th October, 1891.