ioo PROGRESS OF SCIENCE. 



His labours were pursued with unsurpassed success by one 

 who may be called the greatest representative of modern 

 science with Newton, viz. Galileo. 



Galileo invented the earliest (air) THERMOMETER, and 

 improved Janssen's useless TELESCOPE and MICROSCOPE. By 

 the invention of these three instruments, he ensured the rapid 

 development of THERMOLOGY, ASTRONOMY, and PHYSIOLOGY. 

 By means of his telescope, which magnified only eight times, 

 he discovered the SUN'S SPOTS and the revolution of the sun 

 on its axis in 28 days ; discovered the four MOONS OF 

 JUPITER (1610)* demonstrating the Jupiter system to be a 

 miniature of the solar system ; discovered Venus to be a 

 planet of our system, and the phases of that body a discovery 

 which was another solid support of the Copernican doctrine, 

 and caused its general acceptance ; explained the revolutions 

 of the planets to be in the same direction as that of the sun 

 on its axis ; discovered the mountains and valleys of the 

 moon, also the reflection of the earth-light on its dark disk, 

 and determined the true nature of our satellite ; he also 

 determined the true nature of the nebulae resolving some 

 into stars; discovered innumerable fixed stars which had 

 never been seen or suspected by man forty in the 

 PLEIADES alonef a death-blow to the doctrine of the 

 human destiny of the universe, since these bodies could 

 not have been created for the purpose of illuminating the 

 night for human beings. So far the ASTRONOMER. As a 

 MATHEMATICIAN and PHYSICIST, his discoveries were not 

 less important and decisive. 



DYNAMICAL MECHANICS are under great obligation 

 to him. He discovered the LAWS OF FALLING BODIES in 

 which the descent is due to the influence of a permanently 

 acting force (attraction), the velocity increasing (at the rate 

 of 32 feet per second) in consequence thereof; saw that a 



* A fifth moon was discovered (September 9th, 1892) by Professor 

 Barnard (of the Lick Observatory). This is the smallest of Jupiter's 

 satellites ; it is close to the planet (112,000 miles from the centre), makes 

 two revolutions in one day, and is the fastest satellite known to us with 

 the exception of Mars' minor moon, discovered in 1877. 



t There are no less than 2,600 in that system. 



