DISCOVERIES IN THE CELESTIAL SPACES. 317 



the Novum Organon. The invention of the telescope, and 

 the greatest discoveries in physical astronomy (viz., Jupiter's 

 satellites, the sun's spots, the phases of Venus, and the remark- 

 able form of Saturn), fall between the years 1609 and 1612. 

 Kepler's speculations on the elliptic orbit of Mars* were be- 

 gan in 1601, and gave occasion, eight years after, to the com- 

 pletion of the work entitled Astronomia nova seu Physica ce- 

 lestis. " By the study of the orbit of Mars," writes Kepler, 

 " we must either arrive at a knowledge of the secrets of astron- 

 omy, or forever remain ignorant of them. I have succeeded, by 

 untiring and continued labor, in subjecting the inequalities of 

 the movement of Mars to a natural law." The generaliza- 

 tion of the same idea led the highly-gifted mind of Kepler to 

 the great cosmical truths and presentiments which, ten years 

 later, he published in his work entitled Harmonices Mundi 

 libri quinque. " I believe," he well observes in a letter to 

 the Danish astronomer Longomontanus, " that astronomy and 

 physics are so intimately associated together, that neither can 

 be perfected without the other." The results of his researches 

 on the structure of the eye and the theory of vision appeared 

 in 1604 in the Paralipomena ad Vitellionem, and in 161 If 

 in the Dioptrica. Thus were the knowledge of the most im- 

 portant objects in the perceptive world and in the regions of 

 space, and the mode of apprehending these objects by means 

 of new discoveries, alike rapidly increased in the short period 

 of the first ten or twelve years of a century which began with 

 Galileo and Kepler, and closed with Newton*and Leibnitz. 



The accidental discovery of the power of the telescope to 

 penetrate through space originated in Holland, probably in the 

 closing part of the year 1608. From the most recent investi- 

 gations it would appear that this great discovery may be 

 claimed by Hans Lippershey, a native of Wesel and a spec- 

 tacle maker at Middleburg ; by Jacob Adriaansz, surnamed 

 Metius, who is said also to have made burning glasses of ice ; 

 and by Zacharias Jansen.$ The first-named is always called 



1 Delambre, Hist, de V Astronomic Ancienne, t. ii., p. 381. 



t See Sir David Brewster's judgment on Kepler's optical works, in 

 the " Martyrs of Science," 1846, p. 179-182. (Compare Wilde, Gesch. 

 der Optik, 1838, th. i., s. 182-210.) If the law of the refraction of the 

 rays of light belong to Willebrord Snellius, professor at Leyden (1626), 

 who left it behind him buried in his papers, the publication of the law 

 in a trigonometrical form was, on the other hand, first made by Des- 

 cartes. See Brewster, in the North BriHsh Review, vol. vii., p. 207 ; 

 Wilde, Gesch. der Optik, th. i., s.,227. 



I Compare two excellent treatises on the discovery of the telescope, 

 by Professor Moll, of Utrecht, in the Journal of the Royal Institution, 



