io SCIENCE OF THE GREEKS. IT. I. 



was the next Greek who made some important discoveries in 

 science. He invented a sun-dial, by making a flat metal 

 plate with the hours of the day marked upon it in a certain 

 order, so that a large pin, or style as it is called, standing in 

 the middle of the plate, cast a shadow on the right hour 

 whenever the sun shone upon it. You can understand that 

 as the sun is low down in the morning and gradually passes 

 overhead during the day, it will cause the pin to throw its 

 shadow in a different direction at different hours. 



In this way Anaximander taught the Greeks to measure 

 the time of day. He is also said to have been the first as- 

 tronomer who understood why we see the bright face of the 

 moon growing from a crescent to a full moon and then di- 

 minishing again. To know this he must also have known 

 that the moon moves round the earth every month. You can 

 imitate the changes of the moon if you take a round stone 

 and hold it just above your head between you and the sun; 

 you will then have its shady side towards you; pass it slowly 

 round your head, you will find that you see first a bright edge 

 appearing, then more and more of the bright side, till when 

 the stone is on one side of your head and the sun the other, 

 you will see the whole of one side of the stone reflecting the 

 sun's light this is a full moon. Pass it on slowly round, and 

 you will see this bright side disappear gradually till you 

 bring it back to its old position between you and the sun, 

 when it will be again dark. This is what the moon does 

 every month, producing what are called the phases of the 

 moon. Anaximander also made a map of the world, or at 

 least of as much of it as was known in his time. 



Pythagoras, one of the most celebrated of the learned 

 men of Greece, is the next who tells us anything about science. 

 The time and place of his birth is uncertain, but he lived 



