ASTRONOMY OF THE INC AS. 831 



between the smaller towers, being illuminated by the rising or 

 setting sun, were for the solstices, and the towers on the east an- 

 swered to those on the west, at the winter or at the summer sol- 

 stice. In order to verify the event the Inca placed himself in a 

 convenient spot, whence he watched whether the sun rose or set 

 between the two small towers on the east and on the west, and 

 thus the most skilled of the Indians found the astrology of their 

 solstices.* 



This description, equally naive and unintelligible, requires 

 some explanation. The towers and turrets went by fours, two 

 large and two small, and there were two systems, intended for the 

 observation, by one system of the winter solstice, by the other of 

 the summer solstice. In position and relative distances they were 

 so arranged that when the sun reached the tropic of Cancer the 

 shadow cast by the northeastern turret was exactly tangential, at 

 the moment of sunrise, to the southern face of the northwestern 

 turret, and at the same time hid the sun from the amantas on ob- 

 servation in the corresponding tower ; and vice versa at the mo- 

 ment of sunset. As the sky might be cloudy at sunrise, the 

 astronomers posted to observe the setting sun replaced, confirmed, 

 or rectified, when necessary, the determinations of the morning. 

 The southern turrets were used in the system of observatories for 

 the summer solstice. 



Montesinos gives another version which seems different when 

 taken literally, but substantially confirms the former. He relates 

 that the Inca Capac Raymi assembled his learned men and astron- 

 omers to find the solstices. " There was a kind of solar quadrant 

 formed by shadows, and with it they knew what day was long and 

 what other was short, and at what time the sun went toward the 

 tropics and returned from them. I saw four very ancient walls on 

 a hill, and a son of the country afiirmed to me that this building 

 had served the ancient Indians as a clock." Though precise for 

 that time and place, and quite original, no account has been 

 taken in this method of the change in the obliquity of the eclip- 

 tic, forty-eight seconds a year, according to Delambre, the effect 

 of which upon the azimuth is very sensible in those latitudes. 

 Houzeau says that the Incas had no idea of this displacement ; 

 that they observed the June solstice only, and that the continued 

 observations of the amantas proved the absence of a solar calen- 

 dar. It is very possible that the Incas perceived that their observ- 

 atory system finally became useless, and that, without stopping 

 to inquire into the reason, they constructed new ones. There is 

 no doubt that the Incas recognized the movement of the ecliptic 

 some time before the other people of the Old World, but without 



* Garcilaso, Book II, chap, xxiii. 



