REFERENCES.--“Gen. Biogr. Dict.” (Gorton), London, 1833, Vol. I; Hutton’s abridgments of the _Phil. Trans._, London, 1739, Vol. IV. p. 103; “Dict. of Nat. Biog.,” Leslie Stephen, London, 1886, Vol. V. pp. 157 and 271–272; “Gen. Biog. Dict.,” Alex. Chalmers, London, 1812, Vol. V. pp. 370–371; “Biog. Univ.,” Paris, 1843, Vol. IV. p. 397; “Nouv. Biog. Générale” (Hœfer), Paris, 1853, pp. 170–171; Baddam’s abridgments of the _Phil. Trans._, London, 1739, Vol. IV. p. 103; “Ames’ Typog. Antiq.” (Herbert), pp. 693, 694, 697–701; Bloomfield’s “Norfolk,” Vol. LXIV. pp. 68–70; Cooper’s “Athenæ Cantab.”; Davy’s “Suffolk Coll.,” Vol. LXXXIX. p. 215; Hazlitt, “Coll. and Notes,” 1876, also the second series. =A.D. 1609.=--Kepler (Johann), who succeeded Tycho Brahé in 1601 as astronomer to the German Emperor Rudolph II, is the author of a treatise “On the Magnet,” which was followed, during 1609, by his greatest work, the “Astronomia Nova.” The latter was deemed by Lalande of such importance that he considered it the duty of every astronomer to read it from beginning to end at least once in his lifetime. The “Astronomia” contains the extraordinary book “on the motion of Mars,” and is said to hold the intermediate place, besides being the connecting link between the discoveries of Copernicus and those of Newton. Kepler’s doctrine is thus enunciated by Dr. Whewell (“Physical Astronomy,” Chap. I): “A certain Force or Virtue resides in the sun by which all bodies within his influence are carried around him. He illustrates (‘De Stella Martis,’ Chap. XXXIV. p. 3) the nature of this Virtue in various ways, comparing it to Light and to the Magnetic Power, which it resembles in the circumstances of operating at a distance, and also in exercising a feebler influence as the distance becomes greater.” In the Table of Contents of the work on the planet Mars, the purport of the chapter to which allusion has been made is stated as follows: “A Physical speculation, in which it is demonstrated that the vehicle of that virtue which urges the planets, circulates through the spaces of the universe after the manner of a river or whirlpool (vortex), moving quicker than the planets.” It will doubtless be found by any one who reads Kepler’s phrases concerning the _moving force_--the _magnetic nature_--the _immaterial virtue_ of the sun, that they convey no distinct conception, except so far as they are interpreted by the expressions here quoted: “A vortex of fluid constantly whirling around the sun, kept in this whirling motion by the rotation of the sun himself and carrying the planets around the sun by its revolution, as a whirlpool carries straws, could be readily understood; and though it appears to have been held by Kepler that this current and vortex was immaterial, he ascribes to it the power of overcoming the inertia of bodies, and of putting them and keeping them in motion, the only material properties with which he had anything to do.