—, natural, of tourmaline in mica, B. Silliman, Jr., xlvii, 418.

Polarity, new kind of, in light, D. Brewster, xxxv, 292.

— of molecules in crystallization, J. D. Dana, xxx, 275.f

—, electric, see under [Electricity.]

Polarization of heat, xxviii, 366, 397.

— —, remarks on, J. D. Forbes, xl, 317.

— of light by reflection, D. Brewster, xxii, 277.f

— by refraction, laws of, D. Brewster, xxiii, 28f, 227.f

—, use of mica in, J. D. Forbes, xxxviii, 101.

—, elliptical, of reflected light, B. Powell, xliv, 171; xlvi, 390.