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Grow Rapidly:
While these innovations, along with many more minor ones, enabled man to grow greater quantities of food, it seemed that the number of mouths that needed feeding grew almost as rapidly as (and sometimes more rapidly than) his agricultural skills. It is estimated that when man first began farming, the world's population numbered no more than ten million. By the time of Christ, this figure had grown to 250 million; by the mid nineteenth century, 1,000 million; by 1900, 1,650 million; and by 1975 the world population was nearly 4,000 million [7].Igneous rocks [5] are divided into extrusive and intrusive rocks. Extrusive rocks are those that were ejected by volcanoes and cooled as lavas on the surface of the earth. Intrusive rocks are those that solidified beneath the earth's surface. The grain or crystal size of a rock depends on how fast it cooled; coarsegrained rocks are the result of slow cooling which has given crystals time to grow to sizes greater than two millimetres in length. Rocks cool slowly when deep in the earth's crust and coarseness is characteristic of intrusive rocks. Fine-grained rocks have cooled rapidly either on or near the earth's surface; most extrusive rocks are fine grained although some are cooled so rapidly that no crystals have time to grow and obsidian is formed.
As the fry grow and begin to feed they are distributed to other troughs and finally to rearing ponds, constructed in a manner to insure cleanliness and an abundance of flowing water. The young are fed on ground liver and are transplanted when several months old. They grow rapidly, but in the East never attain the large size which they do in their native streams. They feed on insect larvae, etc., and may be fed artificially on chopped beef or liver mixed with corn meal. For angling purposes the rainbow is inferior to the brook-trout, but is a fair substitute.
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