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Each day every person in the United States throws away more than five pounds of rub-bish． There is more rubbish now than ever before and most of it is made up of the packages and cans in which we buy our food．The traditional ways of getting rid of solid wastes is quickly be-coming inadequate(不合适)． Many cities are experimenting with newer ways of handling their growing piles of rubbish．

One of these new ways is "recycling"． Through recycling，usable materials are taken out of wastes and added into something else． These usable parts of wastes are put through the cycle of going from a raw material（原材料） to a finished product again．

In some cities a machine called a hydrapuler (The machine got and named from hydra，which :means "fwater ．)is being used to help recycle rubbish A hydrapuler is like a huge mixing machine．The rubbish is dumped onto endless moving belt that feeds the machine． At the same time，water is pumped into the hydrapuler． With a whirling(旋转) and mixing action，the hydrapuler throws out the．heavy metal objects that can later be sold as waste metal． The rest of the rubbish-paper，food，plastic．rubber，rags，glass，wood，leaves，and other things disintegrates（碎裂） ，or falls apart． The rubbish is then mixed with water and carried in a slush(泥状物) to another piece of equipment where glass，sand and small pieces of metal come out．

With the hydrapuler，up t0 95 percent of the original rubbish is reclaimed． The remainder is turned into ash．

(      ) 21． Rubbish means___________-