To those readers who are really interested in the education of children, M. Leray, the French translator of this book, recommended a series of excellent little works “conceived,” he wrote, “in the very spirit of the ideas developed in this chapter. Their leading principle is that ‘in order to be soundly educative, all teaching must be objective, especially at the outset.’ and that ‘systematical abstraction, if it be introduced into the teaching without an objective (concrete) preparation, is noxious.’” M. Leray meant the series of initiations published by the French publishers, Hachette : Initiation mathématique, by C. A. Laisant, a book completed by the Initiateur mathématique, which is a game with small cubes, very ingenious and giving in a concrete form the proofs of arithmetics, the metric system, algebra and geometry; Initiation astronomique, by C. Flammarion; Initiation chimique, by Georges Darzens; Initiation à la mécanique, by Ch. Ed. Guillaume; and Initiation zoologique, by E. Brucker. The authors of these works had — it would not be just not to mention it — predecessors in Jean Mace’s L’ Arithmétique du grand-papa, and René Leblanc, I, whose excellent manual, Les Sciences physiques à l’Ecole primaire” — M.