ASTRONOMY OF THE INCAS. 829 



offered in October, and in November the princely youth who 

 were to be given arms in the next month had their ears pierced.* 



These Peruvian ceremonials were very like those which Ovid 

 has described. They were not the only ones ; an edict of the Inca 

 Pachacutec mentions three regular festivals occurring in each 

 lunar month ; there were also days for fairs and markets, and a 

 rest day occurring every nine or ten days, like the nondines of 

 the Romans, but not corresponding either with the quarters of 

 the moon or the week, although the phases of the moon were well 

 known to the Incas. As their lunar year fell behind the true 

 time, they rectified their calendar constantly, trying to make it 

 conform roughly with the phases of the moon. 



The hours were not determinate spaces of time corresponding 

 with a mathematical division of the day, but simple indications 

 of such conditions as dawn, or morning, noon, sunset, and night. 



The astronomical observations of the Incas were at first very 

 elementary and empirical. They marked the day when the sun 

 passed over the zenith. An experiment of the simplest character 

 will be sufficient to account for the conclusions they drew from 

 this observation. If we plant a stick vertically, and observe the 

 shadow which it casts when shone upon by the sun, we shall find 

 that at noon toward the end of December, this shadow is very long 

 and directed toward the north ; then it diminishes gradually till 

 the day when it is shortest at noon. In the Southern hemisphere 

 the shadow follows an inverse direction to this, and is longest at 

 noon in June and shortest in December. The days when the 

 shadow is longest, beyond the tropics, are the same for all places 

 in the same hemisphere. But the days when there is no shadow 

 at noon are not the same for all latitudes in the same hemisphere 

 within the tropics. A day's difference exists for every forty kilo- 

 metres. For this reason the Incas established observations at 

 different distances from north to south, over the whole extent of 

 their empire. 



In order to verify the equinoxes, the amantas, or astronomers, 

 arranged richly sculptured columns in the courts of the temples 

 of the sun. On the approach of the equinox, they observed the 

 shadow projected by the columns. These were placed in the 

 center of a large circle through which a line, exactly oriented by 

 experiment, ran from east to west. When they saw that the 

 shadow struck this line in the middle, and that at noon the column 

 was bathed with light on every side, they announced the equinoc- 

 tial day. They then adorned the columns with flowers and fra- 

 grant herbs, and brought offerings of gold, silver, precious stones, 

 and fruit to the god. The gnomon, or column, was surmounted 



* Desjardins. 



