Cassini seemed likely to win for Italy the glory of completing the great structure; but he was sadly fettered by Church influences, and was obliged to leave most of the work to others.
Early among these was Hevel.

He gave reasons for believing that comets move in parabolic curves toward the sun.

Then came a man who developed this truth further--Samuel Doerfel; and it is a pleasure to note that he was a clergyman.

The comet of 1680, which set Erni in Switzerland, Mather in New England, and so many others in all parts of the world at declaiming, set Doerfel at thinking.

Undismayed by the authority of Origen and St.John Chrysostom, the arguments of Luther, Melanchthon, and Zwingli, the outcries of Celich, Heerbrand, and Dieterich, he pondered over the problem in his little Saxon parsonage, until in 1681 he set forth his proofs that comets are heavenly bodies moving in parabolas of which the sun is the focus.