ELEMENTARY NATURAL PHILOSOPHY, DESIGNED FOR HIGH SCHOOLS AND ACADEMIES. BY LA ROY F. GRIFFIN, PROFESSOR OF THE NATURAL SCIENCES AND ASTRONOMY IN LAKE FOREST PHILADELPHIA : 1882. PREFACE. This Natural Philosophy has been written for a text-book for classes that have no further acquaintance with the Mathematics than simple equations and the properties of the square and the parallelogram. It is the result of many years experience in teaching the subject, and the author has tried to present the principles and discussions in such a form as to be readily comprehended by the student. His experience has been that in the use of many text-books upon this subject, a large part of the teacher's time is employed in explaining the language of the text to the pupils, since not only are the ideas of the science new to them, but these ideas are so expressed that the very words are met for the first time. Recollecting that most students begin their acquaintance with the vast field of Natural Science with this branch, an effort has been made to use familiar language, as far as possible, so avoiding too great a transition in their work. The love of science should be developed from the outset. The definitions, especially, have been prepared with an eye to brevity and perspicuity. Since the principles and laws of this science are deduced from experiments, the usual order pursued in the following pages has been to describe the apparatus used and the experiments performed before introducing the laws which result from them. This aids in teaching the student to observe and experiment for himself. Problems illustrating and applying the principles have been introduced throughout Mechanics, and to some extent under the Undulatory Forces, and these have been given |