"With this agrees also the reasonable difference of other animals, and each one being suited to its own use and service. This also is testified by the variety of trees and the diversity of herbs, varying both in form and in juices. This also is asserted by the change of seasons, distinguished into four periods, and the circle closing the year with certain hours, days, months, and not deviating from the appointed reckoning by a single hour. Hence, in short, the age of the world itself is reckoned by a certain and fixed account, and a definite number of years.