Elementary Treatise on Natural Philosophy: Sound and light

æther angle of incidence beam beats body called centimetre centre colours concave mirror conjugate foci convex convex lens corresponding crystal curvature denote density direction displacement distance eclipse emitted employed equal experiment eye-piece flame focal length fork frequency of vibration fundamental note glass harmonics Iceland-spar incident ray index of refraction interval inverted law of sines lens lenses luminous point magnifying medium minimum deviation musical node normal number of vibrations object object-glass oblique observer obtained octave optical ordinary parallel particles pass pencil perpendicular pipe pitch placed plane mirror plate polarization portion position principal axis principal focus prism produced propagation rarefaction ratio reflected ray rotation screen secondary axis seen side slit sonorous spectra spectrum spherical string surface telescope tion tone traversing tube tuning-fork unison velocity of light velocity of sound vertical vibrations per second virtual image visual angle wave-length waves