4. The principal features of the progress of science spoken of in the last chapter are clearly exhibited in these Tables; namely, the _Consilience of Inductions_ and the constant Tendency to Simplicity observable in true theories. Indeed in all cases in which, from propositions of considerable generality, propositions of a still higher degree are obtained, there is a convergence of inductions; and if in one of the lines which thus converge, the steps be rapidly and suddenly made in order to meet the other line, we may consider that we have an example of Consilience. Thus when Newton had collected, from Kepler's Laws, the Central Force of the sun, and from these, combined with other facts, the Universal Force of all the heavenly bodies, he suddenly turned round to include in his generalization the Precession of the Equinoxes, which he declared to arise from the attraction of the sun and moon upon the protuberant part of the terrestrial spheroid. The apparent remoteness of this fact, in its nature, from the other facts with which he thus associated it, causes this part of his reasoning to strike us as a remarkable example of _Consilience_. Accordingly, in the Table of Astronomy we find that the columns which contain the facts and theories relative to the _sun_ and _planets_, after exhibiting several stages of induction within themselves, are at length suddenly connected with a column till then quite distinct, containing the _precession of the equinoxes_. In like manner, in the Table of Optics, the columns which contain the facts and theories relative to _double refraction_, and those which {102} include _polarization by crystals_, each go separately through several stages of induction; and then these two sets of columns are suddenly connected by Fresnel's mathematical induction, that double refraction and polarization arise from the same cause: thus exhibiting a remarkable _Consilience_.