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Stories of the Great Scientists by  Charles R. Gibson




[33] IN the preceding chapter we have seen how Alexander the Great was tutored by the Greek Philosopher Aristotle. Although Alexander did not become a Scientist, we have his name connected indirectly with the great University of these Ancient days. This was the Alexandrian Museum and Library, or what we should now describe as a University. Alexander's connection is that he founded the city of Alexandria, which city soon took the place of Athens as the seat of learning.

The great University was founded by Ptolemy I, King of Egypt, and no expense was spared in the equipment of this great school. Its library is said to have contained seven hundred thousand books, the literature of Rome, Greece, India, and Egypt. This gigantic library was practically destroyed during the siege of Alexandria by Julius Caesar.

Our present interest lies in the lives of the professors and distinguished scholars. Some readers may be surprised to learn that there were as many as fourteen thousand students in this Ancient University.

Unfortunately, we know very little of the lives of these Ancient professors, but the first professor of Mathematics [34] is of special interest to us. This was none other than; Euclid, whose Elements of Geometry  was written two thousand years ago. But his is one of the biographies, which is an entire blank.

Among the other professors of this far-off time was Aristarchus, who with the aid of Geometry attempted to calculate the distance of the Sun and Moon from the Earth. His results were far from the truth; his geometry was right, but his error lay in the measurement of the angle, and that was due to the very imperfect instruments he possessed.

Another succeeding professor, named Eratosthenes, attempted to measure the Earth, and he came remarkably near the truth. His calculation gave the circumference as thirty thousand miles, whereas we know now that it is about twenty-five thousand miles. We have much more accurate means of measuring angles, but it was Eratosthenes who showed us how to measure this great globe upon which we reside, and of which we can only see a very small part at one time. This old Greek Philosopher, at the age of eighty years became blind, and was so wearied of life that he voluntarily starved himself to death.

Another person living about this time, whose name is quite familiar to the general reader, was the great Greek, Mathematician Archimedes. Although Archimedes lived at Syracuse, Sicily, where he was born in 287 B.C., he went as a student to this great University of Alexandria. By that time Euclid had passed away, but other eminent men filled the important posts of professors.

Archimedes was the devoted friend of Hiero, the King of Syracuse; indeed, Archimedes seems to have been a [35] relative of the King, on whose behalf he invented many terrifying engines of war.

To the general reader Archimedes is best known in connection with his detection of the fraud of the jeweller who made King Hiero's crown. It will be remembered that the King had given a certain quantity of pure gold to an artificer to make into a crown, and when the crown was made, the King for some reason or other suspected that he had been cheated. He had suspicions that the jeweller had kept some of the pure gold and used silver to make up the shortage. But the King could not think of any means by which such a fraud might be detected; the crown had the appearance of pure gold and its weight corresponded with the amount of gold supplied by him. In his difficulty he very naturally, consulted his scientific friend Archimedes. The problem puzzled the great mathematician. So much so that his mind became absorbed by it, and on going to the Baths one day he was doubtless trying to seek some solution of the difficulty. His attention was attracted by water overflowing from his bath as he stepped into it. This very simple occurrence suggested a plan by which he might solve the King's difficulty, and jumping out of the bath, and without stopping to dress, he rushed along the streets, shouting in his excitement "Eureka! Eureka!" (I have found it! I have found it!).

Galileo believed that Archimedes had discovered a [36] much more exact method of testing this matter than is given in the story handed down by the Greeks. Galileo's explanation is that Archimedes used a long beam as a. balance, a piece of gold being placed at one end, and weights added to the other end until an exact balance was obtained. Having done this in the ordinary fashion, he allowed the gold to dip into a vessel of water, so that the gold was entirely immersed. Now he found that the gold appeared to weigh less, for it was supported in some measure by the water. Archimedes noted the exact difference in weight. He then repeated the experiment with a piece of silver, noting carefully the exact difference in weights. And again with the crown, which was supported by the water in a manner indicating that its density was intermediate between that of gold and silver. The fraud was apparent. And so Archimedes was the first to discover the laws of hydrostatics.

Archimedes' end was very sudden. His friend King Hiero had died a few years previously at the age of ninety-two. When the Romans took Syracuse in 212 B.C., old Archimedes, then seventy-five years of age, was absorbed in his mathematics. He was busy drawing geometrical figures on the sand, when a Roman soldier rushed upon him. And although Archimedes shouted to him not to spoil his circles, the soldier cut him down. The soldier who thus ended the life of the greatest mathematician of Antiquity must be held responsible for so cruel a deed. For the Roman general Marcellus, who was besieging Syracuse, had given specific instructions that Archimedes and his house were to be spared. It is to the credit of Marcellus that he desired this, for he was aware that the two years' struggle in overcoming Syracuse had been [37] so long only because of the ingenuity of Archimedes. And that the Roman general was sincere in his instructions is evident, for the joy of his triumph over the city was marred when he learnt of the death of Archimedes. Marcellus directed an honourable funeral, and he befriended the relatives of the great mathematician.

By the expressed desire of Archimedes, the figure of a cylinder encircling a sphere was put upon his tombstone, to commemorate his discovery of the relation between the volume of a cylinder and sphere. When the great Roman orator Cicero visited Syracuse one hundred and forty years later, he found the tombstone of Archimedes overgrown with thorns and briars, and he blamed the people of Syracuse for neglecting the memory of their most ingenious citizen.

Returning to our consideration of the great University at Alexandria, of which Archimedes was at one time a student, we come to the name of Hipparchus. We should like very much to study the life of Hipparchus, the real founder of Astronomy, but unfortunately we know nothing whatever of his life. We do not even know whether he acted as a professor in the University, or whether he was merely a student there, but we have a record of his astronomical achievements. As these, however, tell us nothing of the hero himself we must pass them over, except to remark that Hipparchus practically founded that system known later as the Ptolemaic system, which sought to account for the motion of the planets with the Earth as the central body.

This brings us to the name of Ptolemy, another great astronomer at Alexandria, but we should remember that [38] Hipparchus and Ptolemy were separated by three centuries, the former having lived about 160 B.C., and the latter about A.D. 140. Again we find another blank as far as the biography of this great man is concerned. One sometimes finds this great astronomer being confounded with Ptolemy, King of Egypt, who founded the great University of Alexandria, and who was succeeded by a very long line of Ptolemies. Of course, there is no connection between him and the famous astronomer who followed some centuries later.

Ptolemy was also a great geographer, but it is in connection with his planetary system that his name is best known. As already stated, it was the older idea of Hipparchus that Ptolemy extended and perfected. This so-called Ptolemaic system seemed to account so well for the motions of the planets that it held sway for the next fifteen hundred years. We shall see later what trouble Copernicus and Galileo experienced in displacing the Ptolemaic system.

Of course, we shall remember that while Ptolemy's system was counted right for so many centuries, he regarded the Earth as a stationary body in the centre, whereas the real explanation of the Sun being the central body had been taught more than seven hundred years previously.

Ptolemy is the last outstanding figure of this great University of two thousand years ago, and we have seen that our old school friend Euclid was its first professor of mathematics.

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