Cosmos, Vol. 5

Since the first insights that Huygens and Newton, Grimaldi and Robert Hooke had gained into the causal connection between double refraction and interference, one hundred and thirty years had passed without any notable expansion of theoretical optics: until Thomas Young, Malus, Arago, and Fresnel announced the most brilliant discoveries regarding the true nature of interference The phenomenon where two light waves overlap to reinforce or cancel each other out. when light rays cross and travel different paths, both in ordinary and polarized light; regarding polarization The orientation of light waves in a specific direction. through reflection, refraction, and double refraction; as well as regarding chromatic and circular polarization. (Works of Fr. Arago Vol. VII. p. 307, 344—369, 375—392.) These discoveries, and the beautiful works by Fizeau and Foucault (1849 and 1850) prompted by Arago, have proven the groundlessness of the idea of the materiality of light The "corpuscular theory" which suggested light was made of physical particles.; and through the assumption of propagating ether-vibrations The historical belief in a medium called "ether" that carried light waves through space., the most complex optical phenomena have become accessible to mathematical associations (higher analysis) in a fruitful connection that also clarifies meteorology and some parts of physical astronomy. (Arago in the Reports of the Academy of Sciences Vol. VII. 1838 p. 956, Cosmos Vol. III. p. 130.)

In physics as in theoretical chemistry, important generalizations have been presented in groups through the discovery of the law which links the specific heat of simple and compound bodies with their atomic weights in the sense of the convenient and widespread metaphorical language of atomism;9 through the insight into the crystallographic relationships of isomorphism The similarity in crystalline form between different chemical compounds. and the stoichiometric The calculation of relative quantities of reactants and products in chemical reactions. doctrine of chemical equivalents,