Hoovervilles and the economy. As the economic crash of the 1930s dragged on, more and more people were ruined. Delinquent taxes, drastically rising unemployment and mortgage foreclosures were heavy burdens to overcome. Those factors forced ordinary people to either move into Hoovervilles or become transients.
Carbon is the sixth most common element in the universe and the fourth most common element in the solar system. It is the second most common element in the human body after oxygen. About 18 percent of a person's body weight is due to carbon. The black color of smoke is caused by unburned specks of carbon.
Carbon is an extraordinary element. It occurs in more different forms than any other element in the periodic table. The periodic table is a chart that shows how chemical elements are related to each other. More than ten million compounds of carbon are known. No other element, except for hydrogen, occurs in even a fraction of that number of compounds. As an element, carbon occurs in a striking variety of forms. Coal, soot, and diamonds are all nearly pure forms of carbon. Carbon also occurs in a form, discovered only recently, known as fullerenes or buckyballs. Buckyball carbon holds the promise for opening a whole new field of chemistry (see accompanying sidebar).