112 HISTORY OF SCIENCE. 



clined to believe that they were planets revolving very near to the sun, 

 and appearing as black spots when opposed to his luminous disc. He 

 soon saw, however, that the spots belonged to the sun's surface, for 

 they sometimes reappeared in the same order; at other times several 

 spots would unite into one, or a single spot would divide into three 

 or four. They had also different degrees of darkness, and as they ap- 

 proached the edge of the sun's disc he noticed that they always ap- 

 peared to contract in breadth, without losing their length. Finally, he 

 arrived at the true conclusion that the movement of these spots was 

 due to the rotation of the sun about his axis, which occupied a period 

 of about twenty-eight days. Like all Galileo's other discoveries, the 

 announcement of this one led to bitter controversies. Galileo also 

 discovered the bright patches on the sun's surface which are called 

 thkf acute. 



In the year 1 6 1 1 Galileo visited Rome, and was received by the 

 great ecclesiastical dignitaries and others with the consideration due 

 to his talents and reputation. We are informed that he took with him 

 his best telescope, in order to exhibit to his friends at Rome the solar 

 spots, and the crescent form of the planet Venus when in a similar 

 position with regard to the sun as our moon in the first quarter, and 

 his other recent discoveries. While at Rome Galileo joined a scientific 

 society which had not long before been established, and which may 

 be noted as one of the first associations for the encouragement of 

 scientific study. It bore the somewhat fanciful name of the Lyncean 

 Academy, in reference to the acute vision which is supposed to be 

 possessed by the lynx ; and the name was thought emblematic of the 

 penetrating insight that should belong to those who seek to investigate 

 nature. Several of Galileo's minor treatises were originally printed at 

 the expense of the Lyncean Academy. 



Soon after his return from Rome Galileo published at Florence his 

 " Discourse on Floating Bodies," in which he confirms the doctrines 

 of Archimedes on that subject, and refutes by convincing experi- 

 ments the prevailing Aristotelean notion that the sinking or floating 

 of bodies in a liquid depends upori their shapes. The Aristoteleans 

 proclaimed that ice floats upon water, not because it is lighter, " for," . 

 said they, " ice is produced from water by cold, which is attended by 

 condensation." Galileo affirmed that a piece of ice of any shape will 

 float in water, and that ice, so far from being denser than water, was 

 more rarified, and the fact of its floating was the proof of this. 



Galileo's bold manner of announcing new truths, and his energy in 

 defending them against the attacks which never failed to be made 

 upon them, excited much personal hostility against himself and his 

 discoveries ; for the teachers and professors of the older systems found 

 their knowledge and their reputation vanishing together, and were the 

 more exasperated by the sarcasm and ridicule which Galileo some- 

 times resorted to in exposing the absurdities of the current doctrines. 



