Treatise on Physical Optics

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. Those who are acquainted with the Mathematical Theories of Hydrodynamics, Sound and Elasticity on the one hand, and of Electricity and Light on the other, cannot fail to have been struck with the difference, which exists between the two classes of subjects. In the former class, certain equations are obtained, which approximately, though not quite accurately, specify in a mathematical form, the physical state of fluids and solids as they exist in Nature; and the subsequent investigation of these branches of Science, is thereby in great measure reduced to a question of mathematics. As soon as the fundamental equations are established, the subject is brought within the dominion of mathematical analysis, and mathematicians are enabled to exercise their ingenuity and analytical skill, in elaborating and developing the results which flow from them.