Thus cycles revolve within cycles as they revolve even within the smallest cycle, called Throughout the Iron Age, the conditions of the first three cycles prevail one after the other, and when this influence of the Copper Age conditions in the Kali Age spends itself, conditions of darker Kali prevail for a time: Then again signs are visible of Golden Age influence and after a time degenerate into Silver Age phases, then into Copper Age mixed light, then again into the deep gloom of Kali within Kali, and so on. As Kali advances more and more the successive, rotatory influences of the other three cycles become feebler and feebler, and at last under the deepest gloom of Kali gaining fullest power, their influences are kept down absolutely. Here begins the end of the Kali period. Soon after the signs of the coming Golden Age are visible. These ever recurring conditions of the Golden and Silver Ages, though feeble in their influence, counteract the destructive influences of vice and sin and thus help to save the life of Kali from coming to an end all too soon. The Kali Yuga is called the Iron Age, because gold, silver and copper becoming scarcer, people use all sorts of mixed metals, but chiefly iron, in making household utensils, iron being found in great abundance. The average stature of mankind is three and a half cubits or 5 feet 9 inches. Virtue is reduced to one-quarter, the other three-quarters being made up by vice. With the decrease of spirituality ill every succeeding age, the root of vitality has been transferred from marrow to bone, from bone to blood. Now, in the Kali that root of life is destroyed. Life in this age is generally sustained by food alone. The effect of constant concentration upon changeful, external objects rebounds upon the body, causing loss of tissue greater than that in the former ages, which men still have their minds turned inwards, between whiles, to have a dip in the source of All-Life—the soul. The Vedas in the Iron Age are no more understandable to the people in their original sound-embodiments except to a small portion of spiritual Brāhmans. They are therefore presented to the people in general in the form of Shāstras and Purānas. These embody the Vedic truths, principles and ideas in easy constructions and simple language, illustrated by examples and stories drawn from facts in life of the past ages. The Shāstras are, therefore, nothing but the Vedas, simplified, explained and illustrated, with the object of enabling the deteriorated intellect of the Iron Age man to grasp the light and the spirit of the Storehouse of Revealed Wisdom. The ceremonial parts of the Vedas are likewise modified and rendered easier for practice in the form of Smritis (forms of spiritual duties and sacrifices) the daily performance of which is enjoined upon the four-caste people.