27 DECEMBER 1890, Page 24

rather an amplification, of the " Operatives' Lecture " which

Professor Perry delivered at the Leeds meeting of the British Association. The author, on that occasion, had the gyratal, or

spinning-top in his hand, and explained its action viva voce ; now he is driven to put into words what was then presented before the eyes. The first and greatest of spinning-tops—at least of those with which we have to do—is the earth itself. Professor Perry shows in an interesting way how this affects us.