no HISTORY OF SCIENCE. 



observed with the naked eye. Up to this period the only circumstance 

 that had distinguished planets from the fixed stars was their change of 

 place. Now it was proved that they were globes like our earth, and 

 that, like it, they might have moons circling round them. It need hardly 

 be said that in many quarters Galileo's assertions were received with 

 scorn and incredulity. The leading professor of philosophy at Padua 

 absolutely declined to look through Galileo's glass to view for himself 

 the Jovian satellites, though repeatedly urged to do so ; and he proved 

 to the' Grand Duke of Tuscany by the strictest academical deductive 

 reasoning that they could not possibly exist. But Cosmo, having him- 

 self seen the satellites many times, trusted to the evidence of his senses 

 in preference to the professor's syllogisms. Another line of objection 

 was advanced by a Florentine astronomer, which is curious, as it illus- 

 trates the tendency towards the notion that the congruities and pro- 

 portions of numbers, being in some degree pleasant for us to contem- 

 plate as forming very definite mental conceptions, must be found also 

 in nature, in accordance with our preconceptions of her perfections. 

 The reader will remember how completely the system of Pythagoras 

 turned upon doctrines of numerical relations, and so on. It certainly 

 supports our view of the ancient philosophies not being the mere va- 

 garies of individual thinkers, but representative either of some aspect 

 of truth or of some permanent tendency of the human mind, when we 

 find these same notions about numbers still in many instances in- 

 fluencing the minds of the present age. For example, a living as- 

 tronomer of great eminence has published a work in which he traces 

 the most extraordinary relations between the dimensions of a very 

 ancient edifice, the chronology of Jewish history, and the standard 

 British weights and measures. Now, the objections of Sizzi, the Flo- 

 rentine astronomer, to Galileo's Medicean planets, turned upon num- 

 ber. There are, said he, seven openings in the head which commu- 

 nicate with the outer world, namely, two nostrils, two ears, two eyes, 

 and a mouth ; there are seven metals, there are seven days in the 

 week, and many other things are reckoned by sevens, from which we 

 may gather that the number of the planets is necessarily also seven. 

 A similar argument was drawn from the seven branches of the golden 

 candlestick in the Jewish temple, and from the seven Churches of 

 the Apocalypse. Some of Galileo's opponents advanced the most 

 audacious denials of the reality of his discoveries. " The telescope," 

 said one, " does wonders upon the earth, but represents celestial objects 

 falsely. I do not more surely know that I have a soul in my body than 

 that reflected rays are the sole cause of Galileo's erroneous observa- 

 tions. I will never concede his four new planets to that Italian from 

 Padua, though I die for it." 



Galileo soon recognized the fact that Jupiter's satellites might be 

 made the means of solving a problem which was then engaging the 

 attention of astronomers, namely, a method for finding the longitudes 



