Chapter Xii.--Sequel to the Epoch of Young and

FRESNEL.--RECEPTION OF THE UNDULATORY THEORY. 111

CHAPTER XIII.--CONFIRMATION AND EXTENSION OF THE UNDULATORY THEORY. 118

1. Double Refraction of Compressed Glass. 119 2. Circular Polarization. 119 3. Elliptical Polarization in Quartz. 122 4. Differential Equations of Elliptical Polarization. 122 5. Elliptical Polarization of Metals. 123 6. Newton's Rings by Polarized Light. 124 7. Conical Refraction. 124 8. Fringes of Shadows. 126 9. Objections to the Theory. 126 10. Dispersion, on the Undulatory Theory. 128 11. Conclusion. 128