It is well known that study in physics remains incomplete without the practical knowledge. This book is intended for the assistance of students and teachers in Physical Laboratories, to write out the practical details of the different experiments. The general aim of the book is to place before the students a description of a course of experiments which shall not only enable him to obtain a practical associate with methods of measurement, but also as far as possible illustrate the more important principles of the various subjects. Authors aim is to enable the student to make use of his practical work to obtain a clear and more real approaching into the principles of the subjects.