The work, begun so happily by _Copernicus_ and _Kepler_, was completed by the great Englishman, _Newton_ (died 1727). It was he who in his immortal work, _Philosophiae naturalis principia mathematica_, laid bare the law of the universe, which compels the heavenly bodies to revolve about one another. Therewith the laws of _Kepler_, and consequently the Copernican hypothesis, became established. When, in 1727, this scientist, at the age of eighty-five, died, his mortal remains were entombed in Westminster Abbey, the Pantheon of the British nation. Lofty science and the reverent worship of his Creator were combined in the noble mind of this great Briton. In an appendix to his master-work, referred to above, he cited his proofs for the existence of God, and stated that “the entire order, as to space and time of all things existing, must have necessarily proceeded from the conception and will of an existing Being,” that “the admirable arrangement of sun, planets, and comets could only emanate from the decree and the design of an All-wise and Omnipotent Being,” that “we admire Him for His perfections, we adore and worship Him as the ruler of the world, we, the servants of the great Sovereign of the Universe.” According to _Voltaire_, it was stated by _Newton’s_ disciple, _Clarke_, that his master invariably pronounced the name of God with reverent attitude and expression. Inseparably connected with the history of the Copernican system there is the name, which recalls harsh accusations and painful memories, the name of _Galileo_. That he had nothing in common with the aims of those who have broken with faith and Christianity, nor with that hostility against his Church for which his name is so often misused, has been made evident by what we have said on another page (see page 189). Not only during his early life was his religious turn of mind evidenced, but also later on and up to the end of his life he continued to observe faithfully the duties of his religion. One of the greatest physicists of recent times was _Christian Huygens_, who died in 1695 at his native city, The Hague. To him we owe the epoch-making discovery of the undulation of light, while _Newton_ had held light to be a matter of emission. But while _Huygens_ advanced over _Newton_ in this respect, he paid tribute to human limitation by remaining prejudiced against _Newton’s_ theory of gravitation, which he rejected. _Huygens_ was a believing Christian.