461.There is evidence that prehistoric humans used fire as early as 400,000 B. C.
462.In the late 1800's Ellen Richards, began work in the new field of "sanitary science" which was concerned with waste removal, water purification and adequate ventilation.
463.The red clover, high in protein content, is an extremely important leguminous hay and pasture plant of the eastern United States.
464.The topology of Mars is more like that of the Earth than that of any other planet.
465.Ostriches are the largest and strongest of living birds, attaining a height from crown to foot of about 2.4 meters and a weight of up to 136 kilograms.
466.The glaciers that reached the Pacific Coast were valley glaciers, and between those tongues of ice were many sanctuaries that allowed the original forests to survive.
467.As it orbits the Sun, Uranus rotates on its axis, an imaginary line through its center.
468.Ordinarily, tariff duties are placed on commodities according to their value.
469.Folktales sometimes tell stories about individuals who really existed and things that actually happened.
470.Whenever matter in one form is transmuted to another form, a phase change is said to have taken place....
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