Distinctive characters of light completely or partially polarized. LESSONS 32-34. _Theory of Undulations._ Hypothesis of luminous undulations. Vibratory state of a simple ray of homogeneous light. Vibratory state at the intersection of two simple rays of homogeneous light intersecting at a very small angle. Experimental proofs in support of this hypothesis: 1st. Experiment with interferences, fringes. Their breadth is different for different colors; they give the various colors of the prism in white light. The alternately bright and dark sheets are hyperboloids of revolution. The measure of the fringes give the means of estimating the lengths of the undulations corresponding to different colors. 2nd. Colored rings of Newton, observed by reflection, by refraction. Law of the diameters; these vary in absolute length for different colors. Variously colored rings with white light. Reflected rings with a white spot at the center. The theory of the undulations does not apply merely to theses phenomena. Explication of the laws of reflection and refraction. Definition of polarization in the system of waves. Elementary application of double refraction and the polarization which accompanies it in uniaxial crystals when the face of the crystal is parallel to the axis, and the plane of incidence normal or parallel to this axis. _Chemical and Calorific Radiations._ Chemical and calorific radiations are subject, like luminous radiations, to the laws of reflection, refraction, dispersion, double refraction, polarization, interferences. LESSONS 35-36. _Revision._ Considerations on the totality of the subjects of the course. MANIPULATIONS IN PHYSICS. The practical exercises which constitute the subject of this programme will be performed in part by the pupils under the direction of the professors and _répétiteurs_, in part by the professors and _répétiteurs_, with the coöperation of the pupils. _FIRST YEAR._ Use of various instruments, designed for measuring lengths. Experiments on weight with Atwood’s machine, the inclined plane, Morin’s apparatus, and the pendulum. Some experiments on elasticity. Various verifications of the principles of hydrostatics and hydrodynamics. Construction of aerometers. Construction of a barometer, of a manometer. Various verifications of the law of Mariotte. Various experiments with the air-pump. Determination the density of solids or liquids by different methods. Construction of a thermometer. Experiments on the dilatation of liquids and solids by means of the ordinary thermometer and by means of the statical thermometer. Experiments upon the dilatation of air by various methods. Experiments upon the tension of vapors by different methods. Determination of the density of vapors and gases by various methods. Leading experiments on calorific radiation. Experiments on cooling. Determination of specific heats, heats of fusion, heats at which bodies pass into vapor. Cooling mixtures.