PREFACE. Never before in this country has there been so insistent a demand for a more thorough and more comprehensive system of instruction in practical science. Forced by recent events to compare our education with that of other nations, we have suddenly become aware of our negligence in this matter. Industrial and educational experts and commissions are united in demanding a change. While on the whole there has been a steady increase in the amount of time given to science work in the secondary and elementary schools, the attention paid to it, especially in the elementary schools, has been somewhat spasmodic, and its administration has been more or less chaotic. This is not due to lack of interest on the part of school officials but to their dissatisfaction with the methods of instruction employed. There is no doubt that superintendents would gladly introduce more science if they felt sure that the educational results would be commensurate with the time expended. This is indicated by a recent survey of about one hundred and fifty cities in seven states of the Central West. The survey shows that two-thirds of them have nature-study in the elementary schools and that all are requiring some science for graduation from the high school. The average high school is offering three years of science. Since 1890 there has been a greater increase in the percentage of students enrolled in science in the high scl-iools, than in any other subject, and the present enrolment in science is greater than in any other subject. Moreover, greater attention is now being paid to the training of teachers in methods of presentation of science. The chief needs in science instruction today are a more efficient organization of the course of study with a view to its socialization and practical application, and a clear-cut realization on the part of the teacher of the aims, the principles of organization, and the methods of instruction it is to meet these needs that this series is being issued. The books attempt to present such generalizations of science as the average pupil should carry away from his school experience and to organize them for the preparation of the teacher and for presentation to the class. The volumes are therefore of three kinds I source books with accompanying field and laboratory guides for the use of teachers and students in normal schools and schools of education 2 pupils texts and notebooks and 3 books on the teaching of the various science subjects. In the first the material is organized with special reference to the training of the teacher and the most effective methods of presenting the subject to students. In the second the matter is simplified, graded, and arranged in such a way that the books will serve as guides in science work for the pupils themselves...