PREFACE Howehold Physics was written primarily for girls. The principles of physics in such a book are of course the same as in a text-book for boys or for mixed classes. But in household Physics these principles are applied in such a way as to interest girls, by using examples and refererices with which they are thorouglly famiIiar. The work was developed in the classroom. At first the author used an outline, filling in with applications and drawings in the recitation periods. The following year the text was written and mirneograph copies put into the hands of the students. After this material had been carefully- worked over with various classes, it was revised into the present book. The subject of Heat is taken up first, since it is one which has many applications of vital importance to the household. Thus the girl becomes interested in physics from the first, and looks forward to recitations with pleasure. The language of the book has been kept as simple as possible throughout. The topics are carefully explained and these explanations are illustrated by a wealth of line drawings and photographs. The problems are especially easy and practical. The author wishes to take this opporturlity to thank the several industrial concerns which supplied many of the photographs, and also those teachers and pupils who so kindly assisted him in bringing the work to compIetion....