... demand for lead and its products has steadily increased. Lead's usefulness stems from the metal's many desirable properties: softness, high density, low melting point, ability to block radiation, resistance to corrosion, readiness to form alloys and chemical compounds, and ease of recycling. Its versatility, as well as its physical and chemical properties, accounted for its extensive use. Lead can be rolled into sheets which can be made into rods and pipes. It can also be molded into containers and mixed with other metallic elements. Lead was used in ancient times for making coinage, art objects and water pipe ...

... Darwin did not understand how or why variation existed. Today scientists realize that variation arises through random changes (called mutations) to existing genes. Genes are the chemicals that determine the traits and characteristics of animals and plants. Every trait has one or more gene associated with it. Thus, natural selection provides the animals and plants with the best genes. Supporters of neo-Darwinism believe that natural selection operating upon random variation gave rise rise to all animals and plants. While the source of variation is random, the direction of evolution is not. In effe ...

... particular season as does the common cold, although studies show that the most cases are reported during the fall and spring. The actual way that mononucleosis is passed is unknown, although what is known is that the virus can travel in saliva which is the primary source, therefore it may be spread through coughing , mouth to mouth contact of mucous membranes during kissing. This is where the common nickname was derived "the kissing disease". In rare cases this disease may be transmitted through blood transfusions. The disease is usually transmitted to family members, friends and people that you may go ...

... kept in computers. In the early days, we had used papers and pens to record data that we gathered. As a breakthrough technology today, computers have replaced pens and papers. Many businesses are now relying on computers because their statistics and calculations are more accurate than manual calculations. These machines are enabling us to perform many different tasks in less time and making our lives easier. Computers in telecommunications have allowed us to do many things from the comfort of our homes that could never be done before; such as talking with distant friends and relatives, buying merchandise, ...

... floating on the sea of the basaltic ocean floors. The frictional drag along the leading edges of the drifting continents created mountains. Wegener's theory met controversy until 1954, when British geophysicists seeking to explain the phenomenon of polar wandering revived it. Since then, the modern theory of Plate Tectonics has evolved from and replaced Wegener's original thesis. Plate Tectonics is the theory that deals with the structure, history, and dynamics of the earth's crust. The earth's crust is formed of 13 continental plates. The boundaries of the zones are where tectonic activities occur, and where ...

... a often explored subject that interests people of all ages. Parapsychology is one of the most interesting of all sciences. "Most sciences try to explain observable phenomena, parapsychology tries to observe unexplainable phenomena." (http://wheel.ucdavis.edu) This science is widespread throughout the world and pops up in many different cultures. "Scientific methodology in this field dates from the foundation in London of the Society for Psychical Research (1882) which sought to distinguish psychic phenomena from spiritism and to investigate mediums and their activities." (http://wheel.ucdavis.edu) The research star ...

... a classification according to landfill strategy. The EU Draft Landfill Directive recognises three main types of landfill: Hazardous waste landfill Municipal waste landfill Inert waste landfill Similar categories are used in many other parts of the world. In practice, these categories are not clear-cut. The Draft Directive recognises variants, such as mono-disposal - where only a single waste type (which may or may not be hazardous) is deposited - and joint-disposal - where municipal and hazardous wastes may be co-deposited in order to gain benefit from municipal waste decomposition processes. Th ...

... of food is done on the surface of the ground but the behavior of shrews that have been caught suggests that occasionally they may tunnel through dead leaves and loose soil in search of food. The shrews burrow is a small underground number of shallow tunnles under flat stones or logs. Burrows found in east Texas were about 2.5 cm round, from 25 cm to 1.5 m long, and not more than 20 cm below the surface. Each burrow has a large area at the end for the nest which was composed of shredded grass. These nests were used for young or as a resting place for groups of adult shrews. Compared to most types of shrews, t ...

... redeeming feature of DDT is its ability to protect crops from a variety of different pests. This is why DDT is known as the most effective pesticide ever produced (Ray 71). It is proven to have been the most effective chemical ever to prevent the spread of malaria all over the world. It nearly wiped out the disease in some countries altogether. It has been repeatedly proven that DDT does not cause any form of cancer in humans. Contrary to what environmentalist attacks on the pesticide have alleged, the benefits of DDT far exceed the flaws. DDT was first synthesized in 1887 and patented as an insecticide in 1939 ...

... C. The American Indian V. Conclusion We are not Alone. On June 24th, 1947 while searching for the remains of a downed Marine C-46 transport, lost somewhere in the Mount Ranier area, a young Idahoan businessman named Kenneth Arnold spotted something that would change his life forever. Just north of his position flying at an altitude of 9,500 feet and an unprecedented airspeed of 1,700 mph he spotted nine circular aircraft flying in formation. According to his estimate the aircraft were approximately the size of a DC-4 airliner ( Jackson 4). This account was the first sigh ...