What is "four elephants"

As the earth orbits around the sun, the sun's direct point moving orbit in the north and south tropic of cancer, namely, the ecliptic.The ancients will be near the ecliptic sky separated east, south, west and north, and respectively with corresponding representatives of auspicious spirit beast, the four animals image, called four elephants.East seven nights like flying in the late spring early summer night sky dragon, so called east officer black dragon;Northern seven nights like snakes, turtles appeared in summer or early autumn night sky, so called north officer basalt;Western seven nights of tigers jumping out of the night sky of autumn winter so called west officer white tiger.Seven nights like a spread your wings and fly south rosefinch, appear in the winter night sky of early spring, so called south officer zhu exhibition.