GALILEO AND HIS JUDGES. 7 



of Nicholas de Cusa does not appear to have had any 

 extensive circulation it is usual to speak of this 

 system as the Copernican one, notwithstanding the 

 errors from which its great author was unable to 

 extricate himself, and which have long since been 

 rectified by subsequent writers ; so that even at 

 this day we retain the name. 



It is always useful in scientific subjects to intro- 

 duce a definition ; and this is my definition of the 

 sense in which I employ the word Copernican, that it 

 is simply as opposed to the system in which the 

 Earth is the centre of the visible universe, and the 

 Sun revolving about it. It is, in fact, less accurate 

 but more convenient than the employment of the 

 Greek words heliocentric and geocentric to denote the 

 two systems. Greek words, no doubt, abound in our 

 scientific vocabulary, as the following plainly show : 

 astronomy, geology, geography, barometer, thermo- 

 meter, microscope, telescope ; but these have become 

 naturalised in our language by long use, which helio- 

 centric and geocentric have not as yet been. 



After Copernicus there arose an astronomer of 

 great merit, a Dane, Tycho Brahe by name, who 

 attempted to start a fresh system a modification, in 

 fact, of that of Ptolemy. He made all the 

 planets revolve round the Sun, and the Sun, 

 accompanied by the planets, round the Earth. 

 He deserves great credit for his painstaking ob- 

 servations ; but he lived just before the invention of 

 the telescope or, at least, before it was used for 



