SEQUEL TO COPERNICUS. 277 



heliocentric theory, in other ways than by throwing light npon its 

 physical principles. I speak of the new views of the heavens which 

 the Telescope gave ; the visible inequalities of the moon's surface ; the 

 moon-like phases of the planet Venus ; the discovery of the Satellites 

 of Jupiter, and of the Ring of Saturn. These discoveries excited at 

 the time the strongest interest ; both from the novelty and beauty of 

 the objects they presented to the sense ; from the way in which they 

 seemed to gratify man's curiosity with regard to the remote parts of 

 the universe ; and also from that of which we have here to speak, 

 their bearing upon the conflict of the old and the new philosophy, the 

 heliocentric and geocentric theories. It may be true, as Lagrange 

 and Montucla say, that the laws which Galileo discovered in Mechan- 

 ics implied a profounder genius than the novelties he detected in the 

 sky : but the latter naturally attracted the greater share of the atten- 

 tion of the world, and were matter of keener discussion. 



It is not to our puqDose to speak here of the details and of the occa- 

 sion of the invention of the Telescope ; it is well known that Galileo 

 constructed his about 1G09, and proceeded immediately to apply it to 

 the heavens. The discovery of the Satellites of Jupiter was almost 

 immediately the reward of his activity ; and these were announced in 

 his Nuncius Sidereus, published at Venice in 1G10. The title of this 

 work will best convey an idea of the claim it made to public notice : 

 " The Sidereal Messenger, announcing great and very wonderful spec- 

 tacles, and offering them to the consideration of every one, but espe- 

 cially of philosophers and astronomers ; which have been observed by 

 Galileo Galilei, &c, &c, by the assistance of a perspective glass lately 

 invented by him ; namely, in the face of the moon, in innumerable 

 fixed stars in the milky-way, in nebulous stars, but especially in four 

 planets which revolve round Jupiter at different intervals and periods 

 with a wonderful celerity ; which, hitherto not known to any one, the 

 author has recently been the first to detect, and has decreed to call the 

 Medicean stars." 



The interest this discovery excited was intense : and men were at 

 this period so little habituated to accommodate their convictions on mat- 

 ters of science to newly observed facts, that several of the " paper-phi- 

 losophers," as Galileo termed them, appear to have thought they could 

 get rid of these new objects by writing books against them. The effect 

 which the discovery had upon the reception of the Copernican system 

 was immediately very considerable. It showed that the real universe 

 was very different from that which ancient philosophers had imagined, 



