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SCIENCE. 



[N. S. Vol. XX. No. 508. 



point. Hence a body as large as our earth, 

 which was known to be a globe from the 

 time that the ancient Phoenicians navigated 

 the Mediterranean, if placed in the heavens 

 at a sufficient distance, would look like a 

 star. The obvious conclusion that the stars 

 might be bodies like our globe, shining 

 either by their own light or by that of the 

 sun, would have been a first step to an un- 

 derstanding of the true system of the world. 



There is historic evidence that this de- 

 duction did not wholly escape the Greek 

 thinkers. It is true that the critical stu- 

 dent will assign little weight to the cui-rent 

 belief that the vague theory of Pythagoras 

 that fire was at the center of all things, 

 implies a conception of the heliocentric 

 theory of the solar system. But the testi- 

 mony of Archimedes, confused though it 

 is in form, leaves no serious doubt that 

 Aristarchus of Samos not only propounded 

 the view that the earth revolves both on its 

 own axis and around the sun, but that he 

 correctly removed the great stumbling- 

 block in the way of this theory by adding 

 that the distance of the fixed stars was 

 infinitely greater than the dimensions of 

 the earth's orbit. Even the world of phi- 

 losophy was not yet ready for this concep- 

 tion, and so far from seeing the reasonable- 

 ness of the explanation, we find Ptolemy 

 arguing against the rotation of the earth 

 on grounds which careful observations of 

 the phenomena around him would have 

 shown to be ill foiinded. 



Physical science, if we can apply that 

 term to an uncoordinated body of facts, 

 was successfully cultivated from the earli- 

 est times. Something must have been 

 known of the properties of metals, and the 

 art of extracting them from their ores must 

 have been practised from the time that 

 coins and medals were first stamped. The 

 properties of the most common chemical 

 compounds were discovered by alchemists 

 in their vain search for the philosopher's 



stone, but no actual progress worthy of the 

 name rewarded the practitioners of the 

 black art. 



Perhaps the first approach to a correct 

 method was that of Archimedes who, after 

 careful thinking, worked out the law of 

 the lever, reached the conception of the 

 center of gravity, and demonstrated the 

 ■ first principles of hydrostatics. It is, 

 therefore, all the more remarkable that he 

 did not extend his researches into the phe- 

 nomena of motion, whether spontaneous or 

 produced by force. The stationary condi- 

 tion of the human intellect was most 

 strikingly illustrated by the fact that not 

 until the time of Leonardo was any sub- 

 stantial advance made on his discovery. 

 To sum up in one sentence the most char- 

 acteristic feature of ancient and medieval 

 science, we see a notable contrast between 

 the precision of thought implied in the con- 

 struction and demonstration of geometrical 

 theorems and the vague, indistinct char- 

 acter of the ideas of natural phenomena 

 generally, a contrast which did not disap- 

 pear until the foundations of modern sci- 

 ence began to be laid. 



We should miss the most essential point 

 of the difference between medieval and 

 modern learning if we looked upon it as 

 mainly a difference either in the precision 

 or the amount of knowledge. The devel- 

 opment of both of these qualities would, 

 under any circumstances, have been slow 

 and gradual, but sure. We can hardly 

 suppose that any one generation, or even 

 any one century, would have seen the com- 

 plete substitution of exact for inexact ideas. 

 Slowness of growth is as inevitable in the 

 case of knowledge as in that of a growing 

 organism. The most essential point of dif- 

 ference is one of those seemingly slight 

 ones, the importance of which we are too 

 apt to overlook. It was like the drop of 

 blood in the wrong place, which some one 

 has told us makes all the difference between 



