COPPERNICUS 169 



theless fixing clearly in the mind of the reader that a simple 

 way exists to measure these distances and magnitudes, and 

 that this is all a part of the solid chain of his theory. 



In the fifth book he sketches the placing and the motion of 

 the planets, determines their relative distances, and for the first 

 time in history, so far as we know, the human eye has seen 

 the world machine in motion, just as it is. True, he does not 

 see it whole ; he knows nothing, of course, of the two outer- 

 most planets, Uranus and Neptune. He knows nothing of the 

 asteroids, of the " shattered planet " ; he knows nothing of the 

 moons of Jupiter, and neither for him nor for any man for a 

 long time after do the comets come and go in obedience to 

 natural law. 



But such of it as his unarmed eyes could see, he saw true. 

 For the first time, so far as we know, all of the known planets 

 were set in their true position, with the sun at their centre of 

 motion. Some of the ancients, Apollonius of Perga perhaps, 

 had correctly pictured Mercury and Venus as satellites of the 

 sun. Aristarchus, in picturing the motion of the earth, must 

 have conceived the moon describing its epicyclic motion about 

 the moving earth, and having caught the truth so near, he may 

 have seen it all ; we do not know. If he left any treatise other 

 than the slender brochure which has come down to us, it is 

 lost. More sheerly than it has been given to many great dis- 

 coverers in the history of science, Coppernicus' vast theory 

 was his own. 



He quoted little ; he showed, indeed, a kind of aloof in- 

 difference to the opinion of friend or foe. He must have cared 

 but slightly for applause. He seems to have shared something 

 of the old Pythagorean idea that the truth was for the elect 

 alone. It was his original intention to communicate his theory 

 only to friends. You catch a little of his spirit when he refers 

 to Lactantius, " who had spoken so childishly of the form of 

 the earth, deriding those who held it to be spherical." He 

 observes : "On mathematical subjects one should write only 

 to mathematicians." His style is simple, homely, direct. Occa- 

 sionally you feel that his quiet pulses might, in TyndalTs phrase, 

 have been the seat of a nascent thrill. Defending his helio- 

 centric arrangement of the planets, there is a passage which 

 runs : 



"By no other arrangement have I been able to find so 



