Religious ceremonials were closely connected with the daily life of the people, and especially with the course of the seasons and the succession of months, as they affected the operations of agriculture. It was important to fix the equinoxes and solstices, and astronomical knowledge was a part of the priestly office. There were names for many of the stars; their motions were watched as well as those of the sun and moon; and though a record of the extent of the astronomical knowledge of the Incas has not been preserved, it is certain that they watched the time of the solstices and equinoxes with great care, and that they distinguished between the lunar and solar years. Pillars were erected to determine the time of the solstices, eight on the east and eight on the west side of Cuzco, in double rows, four and four, two low between two higher ones, twenty feet apart. They were called _Sucanca_, from _suca_, a ridge or furrow, the alternate light and shade between the pillars appearing like furrows. A stone column in the centre of a level platform, called _Inti-huatana_, was used to ascertain the time of the equinoxes. A line was drawn across the platform from east to west, and watch was kept to observe when the shadow of the pillar was on this line from sunrise to sunset, and there was no shadow at noon. The principal _Inti-huatana_ was in the square before the great temple at Cuzco; but there are several others in different parts of Peru. The most perfect of these observatories is at Pissac, in the valley of Vilcamayu.[1185] There is another at Ollantay-tampu, a fourth near Abancay, and a fifth at Sillustani in the Collao. There is reason to believe that the Incas used a zodiac with twelve signs, corresponding with the months of their solar year. The gold plates which they wore on their breasts were stamped with features representing the sun, surrounded by a border of what are probably either zodiacal signs or signs for the months. Whether the ecliptic, or _huatana_, was thus divided or not, it is certain that the sun’s motion was observed with great care, and that the calendar was thus fixed with some approach to accuracy.[1186] The year, or _Huata_, was divided into twelve _Quilla_, or moon revolutions, and these were made to correspond with the solar year by adding five days, which were divided among the twelve months. A further correction was made every fourth year. Solar observations were taken and recorded every month. The year commenced on the 22d of June, with the winter solstice, and there were four great festivals at the occurrence of the solstices and equinoxes.[1187]