78 COSMOS, 



Brahe, the most exact of the measuring astronomers of that 

 great age, had been dead seven years. I have already men- 

 tioned, in a preceding volume of this work (see p. 711), that 

 none of Kepler's contemporaries, Galileo not excepted, be- 

 stowed any adequate praise on the discovery of the three laws 

 which have immortalised his name. Discovered by purely 

 empirical methods, although more rich in results to the whole 

 domain of science, than the isolated discovery of unseen cosmical 

 bodies, these laws belong entirely to the period of natural 

 vision, to the epoch of Tycho Brahe arid his observations; 

 although the printing of the work entitled Astronomia nova 

 seu Physica coelestis de motibus Stellce Martis, was not com- 

 pleted until 1609, and the third law, that the squares of the 

 periodic times of revolution of two planets are as the cubes of 

 their mean distances, was first fully developed in 1619, in the 

 Harmonice Mundi. 



The transition from natural to telescopic vision which cha- 

 racterizes the first ten years of the seventeenth century, was 

 more important co astronomy (the knowledge of the regions of 

 space), than the year 1492, (that of the discoveries of Columbus) 

 in respect to our knowledge of terrestrial space. It not only in- 

 finitely extended our insight into creation, but also, besides en 

 riching the sphere of human ideas, raised mathematical science 

 to a previously unattained splendour, by the exposition of new 

 and complicated problems. Thus the increased power of the 

 organs of perception re-acts on the world of thought, to the 

 strengthening of intellectual force, and the ennoblement of 

 humanity. To the telescope alone we owe the discovery, in 

 less than two-and-a-half centuries, of thirteen new planets, 

 of four satellite-systems, (the four moons of Jupiter, eight 

 satellites of Saturn, four, or perhaps six of Uranus, and one of 

 Neptune), of the sun's spots and faeulee, the phases of Venus, 

 the form and height of the lunar mountains, the wintry polar 

 tones of Mars, the belts of Jupiter and Saturn, the rings of 



