TEE GENESIS OF THE LAW OF GRAVITY 2,19 



III. The system seemed adequate, was geocentric and appealed to 

 the popular imagination. 



Some of the more obvious criticisms of the system may be men- 

 tioned : 



I. The ancients believed the sun to be larger than the earth — it 

 would be more likely to be the center of the system. 



II. The diurnal motion of the earth offered a simple explanation 

 of the apparent motion of the heavens — the simple should prevail when 

 opposed to the complex. 



III. The Pythagorean system gave the same law of motion (the 

 circle) to all the members of the system, while in the Ptolemaic system 

 the moon and sun moved in circles and the rest in epicycles. 



The cumbersome Ptolemaic system, having been adopted, became 

 with the passage of time deeply rooted in the philosophy and religion 

 of the race. Its complexity became greater and greater, for with more 

 accurate observations came the necessity of adding "cycle on epicycle, 

 orb on orb " to keep track of the required corrections. It is not sur- 

 prising, therefore, to find Alphonso X., in the thirteenth century, when 

 contemplating the system, exclaiming, " if the Deity had called him to 

 His councils at the creation of the world, he could have given Him 

 good advice." Indeed the system finally crumbled and fell from the 

 very weight of its superstructure. 



We have spoken of the ravages of time and of war as hindering the 

 progress of knowledge. We have now to note the greatest calamity that 

 has in modern history overtaken the cause of human knowledge. In 

 the third century before Christ, was founded the Alexandrian library 

 with its treasures of art, of literature and of science collected from 

 every part of the known world. Century by century it grew, and could 

 it have survived what untold treasures would have been ours to-day ! 

 But in the seventh century a.d. the Caliph Omar in a day reduced to 

 ashes this storehouse of wisdom, and by one act set the world back a 

 thousand years. Perhaps this disaster can be overrated; perhaps, in 

 the dissemination of copies of the old masters, the Alexandrian library 

 had done its real work; but to me it seems otherwise; for many a 

 priceless gem of literature and of science must have perished in the 

 wanton Arab's destruction. As a single example, it is doubtless due 

 to this cause that we have none of the astronomical writings of Hip- 

 par chus. 



To Alphonso X., of Castile, belongs the honor of being the first 

 European monarch to foster astronomy. In the thirteenth century he 

 founded a college in Toledo, and gathered together savants from all 

 parts of his realm. From the Arabs they acquired much both in 

 mathematics and in astronomy. Original sources were also sought out 

 in the Greek. Other schools were rapidly established and centers of 



