The author has created a series of books on the natural sciences carefully adapted to the different periods of the course of study, with this textbook intended for the older scholars in what are commonly called grammar-schools. At the same time they are suited to scholars who are advanced to a higher grade who have not gone through the previous books of the series. The general plan and style of these books are very different from what are seen in most of the books for schools on the same subjects. The order of the subjects and the mode of developing them differ from the stereotype plan which has so generally been adopted. One prominent feature is the free use of illustrations from familiar phenomena. It makes the books suitable for use in the family as well as the school, between which there should be more common ground than the present mode of education allows.