The Theory of Universal Gravitation, and of the Undulatory Theory of Light, are, indeed, full of examples of this Consilience of Inductions. With regard to the latter, it has been justly asserted by Herschel, that the history of the undulatory theory was a succession of _felicities_[15\2]. And it is precisely the unexpected coincidences of results drawn from distant parts of the subject which are properly thus described. Thus the Laws of the _Modification of polarization_ to which Fresnel was led by his general views, accounted for the Rule respecting the _Angle at which light is polarized_, discovered by Sir D. Brewster[16\2]. The conceptions of the theory pointed out peculiar _Modifications_ of the phenomena when _Newton's rings_ were produced by polarised light, which modifications were {90} ascertained to take place in fact, by Arago and Airy[17\2]. When the beautiful phenomena of _Dipolarized light_ were discovered by Arago and Biot, Young was able to declare that they were reducible to the general laws of _Interference_ which he had already established[18\2]. And what was no less striking a confirmation of the truth of the theory, _Measures_ of the same element deduced from various classes of facts were found to coincide. Thus the _Length_ of a luminiferous undulation, calculated by Young from the measurement of _Fringes_ of shadows, was found to agree very nearly with the previous calculation from the colours of _Thin plates_[19\2]. [Note 15\2: See _Hist. Ind. Sc._ b. ix. c. xii.] [Note 16\2: _Ib._ c. xi. sect. 4.] [Note 17\2: See _Hist. Ind. Sc._ b. ix. c. xiii. sect. 6.] [Note 18\2: _Ib._ c. xi. sect. 5.] [Note 19\2: _Ib._ c. xi. sect. 2.] No example can be pointed out, in the whole history of science, so far as I am aware, in which this Consilience of Inductions has given testimony in favour of an hypothesis afterwards discovered to be false. If we take one class of facts only, knowing the law which they follow, we may construct an hypothesis, or perhaps several, which may represent them: and as new circumstances are discovered, we may often adjust the hypothesis so as to correspond to these also. But when the hypothesis, of itself and without adjustment for the purpose, gives us the rule and reason of a class of facts not contemplated in its construction, we have a criterion of its reality, which has never yet been produced in favour of falsehood.