But even after the omission of all cometary objects we can still count in the solar system upwards of five hundred bodies, almost every one of which pronounces distinctly, though with varying emphasis, in favour of the nebular theory.
His observations of the great comet of January 1672 supplied the basis of modern cometary astronomy.
The prize was again awarded to Lagrange; and he earned the same distinction with essays on the problem of three bodies in 1772, on the secular equation of the moon in 1774, and in 1778 on the theory of cometary perturbations.
In the Berlin Memoirs for 1778 and 1783 Lagrange gave the first direct and theoretically perfect method of determining cometary orbits.
It has not indeed proved practically available; but his system of calculating cometary perturbations by means of "mechanical quadratures" has formed the startingpoint of all subsequent researches on the subject.
In addition to magnesium and sodium the lines of potassium, lithium and also the carbon flutings exhibited in cometary spectra, has been seen.
In 1868 he proved incandescent carbon-vapours to be the main source of cometary light; and on the 23rd of April in the same year applied Doppler's principle to the detection and measurement of stellar velocities in the line of sight.
He studied medicine at GÃ¶ttingen, 1 7771 7 80, attending at the same time Kaestner's mathematical course; and in 1779, while watching by the sick-bed of a fellow-student, he devised a method of calculating cometary orbits which made an epoch in the treatment of the subject, and is still extensively used.
His great contribution to astronomy dates from 1866, when he showed that meteors or shooting stars traverse space in cometary orbits, and, in particular, that the orbits of the Perseids and Comet III., 1862, and of the Leonids and Comet I., 1866, were practically the same.