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

## BOOK X.

HISTORY OF THERMOTICS AND ATMOLOGY.

Introduction. 137

_THERMOTICS PROPER._

##