222 THE WORLD MACHINE 



been observed. When it reached the borders of the sun he 

 was able to follow its exit distinctly ; there could be no doubt 

 that it was in reality the planet. He had the pleasure of ob- 

 serving a phenomenon unknown to antiquity ; he liked a good 

 phrase, and in allusion to the ancient quest for the philosopher's 

 stone, he said : "I have seen what sages have sought with 

 such ardour ; I have found Mercury in the sun." 



It was one more heavy buttress added to the Coppernican 

 fabric. In the ancient Ptolemaic system, Mercury had been 

 set in revolution round the earth like Venus and the sun ; but 

 it was difficult on this theory to understand how Mercury could 

 be eclipsed by the sun and march across its face as well. The 

 thing was simply inexplicable. 



Gassendi sought likewise the transit of Venus, equally pre- 

 dicted by Kepler for a month later. Unluckily for him and 

 for other observers, awakened by his discovery of the transit 

 of Mercury, the passage of Venus seems to have occurred during 

 the night. At any rate the first actual observation was reserved 

 for a young Englishman, Robert Horrox, eight years later. 



Gassendi was a voluminous writer ; several astronomical works 

 were among the number. He had in a high degree the historical 

 sense ; he was one of the earliest of the moderns to adopt the 

 historical form in the treatment of scientific questions. He 

 wrote excellent lives of Coppernicus and of Tycho Brahe", on 

 the life and death of Epicurus as well ; it is by the latter work, 

 perhaps, that he is best known. His criticisms of Descartes 

 were models of polemic, keen, politely ironical, good-natured, 

 and substantial none the less. He was the first to point out 

 that the principle of doubt expounded by Descartes was but a 

 fiction, and that the famous " I think, therefore I am " involves 

 a quantity of dogmas no one of which have we any absolute 

 proof for whatever. He anticipated the nihilism of Berkeley 

 by a century. 



Of interest merely as noting the advancement of the new 

 ideas, was the unqualified adhesion to the Coppernican doctrine 

 by the English philosopher Hobbes. While Bacon was making 

 the ideas of Gilbert, Harvey, and Coppernicus a triangular 

 target for his fretful animadversions, the father of English 

 materialism boldly embraced them all. It is true that he was 

 only thirty-two when the Novum Organum appeared, and that 



