X. On the elliptic polarization of light by reflexion from metallic surfaces

In a former paper, inserted in the Philosophical transactions, 1843, Part I., I detailed observations on some phenomena of elliptic polarization by reflexion from certain metallic surfaces; but with reference only to one class of comparative results. From these I have been led to pursue the subject into other relations besides those at first contemplated; but, from various causes, have only been able tat this interval to submit to the results to the Royal Society as a sequel to my former observations. The changes in the degree of ellipticity, investigated in my former paper, correspond to certain changes in the thickness of metallicfilms . If we now consider the case of reflexion from asimple polished metallic surface , and admit that in this case it may be supposed to take place by the penetration of the ray to a certain minute depth, or to some action of a thin transparent lamina of the metal, then, in like manner, —dependent on the law of metallic retardation, —the effect would vary with a difference in theeffective thickness of the lamina, produced by changing the inclination of the incident ray; and that this is the case in general is well known, viz. that as the incidence is increased, the ellipticity increases up to a maximum, which occurs for most metals at an incidence between 70° and 80°, beyond which it decreases up to 90°.