British Columbia is the third largest Canadian provinces, both in area and population. It is nearly 1.5 times as... [查看全文]
Botany, the study of plants, occupies a peculiar position in the history of human knowledge. For many thousands ... [查看全文]
Scattered through the seas of the world are billions of tons of small plants and animals called plankton. Most ... [查看全文]
An important new industry, oil refining, grew after the Civil war. Crude oil, or petroleum – a dark, thick... [查看全文]
The theory of plate tectonics describes the motions of the lithosphere, the comparatively rigid outer layer of th... [查看全文]
Icebergs are among nature’s most spectacular creations, and yet most people have never seen one. A vague ai... [查看全文]
Topaz is a hard, transparent mineral. It is a compound of aluminum, silica, and fluorine. Gem topaz is valuable.... [查看全文]
If the salinity of ocean waters is analyzed, it is found to vary only slightly from place to place. Nevertheles... [查看全文]
Atmospheric pressure can support a column of water up to 10 meters high. But plants can movewater much higher; ... [查看全文]
Collectibleshavebeenapartofalmosteveryculturesinceancienttimes.Whereassomeobjectshavebeencollectedfortheirusefulness,othershavebee... [查看全文]