Suburbanization If by suburb is meant an urban margin that grows more rapidly than its already developed interior, the process of suburbanization began during the emergence of the industrial city in the second quarter of the nineteenth century. Befor...
Statistics There were two widely divergent influences on the early development of statistical methods. Statistics had a mother who was dedicated to keeping orderly records of governmental units (state and statistics come from the same Latin root stat...
Sleep Sleep is part of a person's daily activity cycle. There are several different stages of sleep, and they too occur in cycles. If you are an average sleeper, your sleep cycle is as follows. When you first drift off into slumber, your eyes will ro...
Skyscrapers and Environment In the late 1960's,many people in North America turned their attention to environmental problems,and new steel-and-glass skyscrapers were widely criticized.Ecologists pointed out that a cluster of tall buildings in a city...
Scientific Theories In science, a theory is a reasonable explanation of observed events that are related. A theory often involves an imaginary model that helps scientists picture the way an observed event could be produced. A good example of this is...
Schooling and Education It is commonly believed in the United States that school is where people go to get an education.Nevertheless, it has been said that today children interrupt their education to go to school. The distinction between schooling an...
Raising Oysters In the past oysters were raised in much the same way as dirt farmers raised tomatoes - by transplanting them. First, farmers selected the oyster bed, cleared the bottom of old shells and other debris, then scattered clean shells about...
Pottery Ancient people made clay pottery because they needed it for their survival. They used the pots they made for cooking, storing food, and carrying things from place to place. Pottery was so important to early cultures that scientists now study...
Population Growth The growth of population during the past few centuries is no proof that population will continue to grow straight upward toward infinity and doom. On the contrary, demographic history offers evidence that population growth has not b...
Police and Communities Few institutions are more important to an urban community than its police, yet there are few subjects historians know so little about. Most of the early academic interests developed among political scientists and sociologists,...
Plate Tectonics and Sea-floor Spreading The theory of plate tectonics describes the motions of the lithosphere, the comparatively rigid outer layer of the Earth that includes all the crust and part of the underlying mantle.The lithosphere is divided...
Plants in the Deserts Some cacti, like the saguaro, grow to tree size, but true trees need more moisture than most desert environments can supply, so they are scarce on deserts. Close to streambeds, cottonwoods can sometimes be found. Though these st...
Plankton Scattered through the seas of the world are billions of tons of small plants and animals called plankton. Most of these plants and animals are too small for the human eye to see. They drift about lazily with the currents, providing a basic f...
Piano The ancestry of the piano can be traced to the early keyboard instruments of the fifteenth and sixteenth centuries -- the spinet, the dulcimer, and the virginal. In the seventeenth century the organ, the clavichord, and the harpsichord became t...
Oil Refining An important new industry, oil refining, grew after the Civil War. Crude oil, or petroleum -- a dark, thick ooze from the earth -- had been known for hundreds of years, but little use had ever been made of it. In the 1850's Samuel M. Kie...
