This series of texts is based on the theory that the success ful citizen should know the chemical, physical, and biological forces with which he has to contend; that he should under stand the laws under which these forces operate; and that he should acquire some skill in directing them. He should ultimately become able to adjust and correlate these forces so as to bring them all under the orderly operation of economic law. In conformity with the above theory this series has been made to cover the following fundamental divisions.