91色情片

In Cycles of Life: Civilization and the Biosphere (Scientific American
Library, $32.95, ISBN 0 7167 5079 1), Vaclav Smil tracks some of the
crucial chemical elements of life鈥攃arbon, nitrogen, sulphur鈥攁s they
are recycled through the ages, from cell to cell, rock to water, from the dead
to the living. Its presentation is populist: Smil portrays these chemical
journeys through the ages and through the biosphere as a kind of Hollywood
intrigue in which the star players are the chemicals of life rather than the
life forms which they make up. It is extremely well informed. He tells of the
huge extent to which we have interfered with the natural cycles of these
elements, transferring unprecedented amounts of carbon, nitrogen and sulphur to
the atmosphere, and challenges the human race to reduce this interference, for
its own sake.