ii4 SECTION PHYSICS. 



maculas. Solem incumbrantes aliud non vtilt esse, etc." Hero it is 

 beyond all doubt that Galileo was the first to discover the solar 

 spots, upon which he afterwards wrote his " Lettere Solari," in 1613, 

 in which he rebuffs, with solid arguments, all the objections raised 

 against him ; gives an account of the spots, teaches the way to draw 

 them on paper, and, with happy intuition, compares them to terres- 

 trial clouds ; speaks of the rotation of the sun on its own axis, and 

 admits that that luminary, to maintain its own heat, must be con- 

 tinually requiring fresh aliment (pabulo). 



Another important work of Galileo is the one entitled, " Concerning 

 the Things that Float on the Water, or that Move in it," in which, for 

 the first time, light is thrown upon the principle of potential velo- 

 cities. Most important, then, is his " Saggiatore," which was pub- 

 lished in 1623, in answer to an astronomical work of the Jesuit 

 Grassi, chiefly on the subject of comets. Among the many treatises 

 which Galileo wrote, are some in which may be discerned the founda- 

 tions of the sciences of hydrostatics and hydraulics ; and it is certain 

 that he conceived and made use of the theory of indivisibles before 

 his disciple the celebrated Cavalicri. Coming to the " Dialogue on 

 the Great Systems of the Universe," which brought such persecution 

 on Galileo's head, it will not be out of place to recall how his incom- 

 parable knowledge and honesty and frankness brought clown upon 

 him the envy and hatred of the greater part of the clergy. That body 

 knew full well that they could not for long battle against the light of 

 truth, by means of the dark mist in which they had sought to en- 

 velop the minds of men, in order that every appearance of knowledge 

 should belong to them alone, the absolute masters of the human con- 

 science. At each new publication or discovery by Galileo there 

 never failed a most bitter storm of reproof, incited by that caste which 

 most of all hated and feared him, and which was often most disgrace- 

 fully supported by some peripatetic, who, measuring Aristotle's vast 

 mind by his own most limited intelligence in interpreting him, could 

 not conceive that if that great philosopher were now to know of one 

 of Galileo's sublime conjectures, very different would be his reasoning 

 on the nature of things. It is enough to mention, that to such an 

 extent was the hostility towards Galileo carried, mainly through the 

 agency of the Dominicans, that one of them, Fra Tommaso Caccini. 



