书城教材教辅科学读本(英文原版)(套装1-6册)
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第162章 第二册(79)

"See what I have here," Fred went on. "It is a sheet of tin as thin as paper. It would take a thousand sheets like this, laid one upon another, to make a pile an inch high. It is called tin-foil. I took it off a packet of sweetmeats this morning. It is used for wrapping up sweetmeats, fancy soaps, tobacco, and all articles that have to be kept from the air. See, it is so pliable that it folds closely over the things. Can you tell me how this tin-foil is made, Norah?""It must be either beaten or rolled out," saidNorah. "I suppose it was rolled out."

"Yes," said Fred, "it was. What does that tell us about tin?""It tells us that tin is a malleable metal.""Tin, like other metals, is always found as an ore. It must be smelted in a furnace, to remove the earthy parts, before it can be of use."SUMMARY

Tin is a white metal, with a bright lustre. It is very fusible and malleable. "Tinned ware" is made of sheet-iron dipped into melted tin. The tin forms a coat over the iron. The iron itself would rust; tin does not easily rust, and can be rubbed up when it gets dull.

Lesson 36

Three Classes of Monkeys

"Teacher showed us some fine pictures of monkeystoday, Norah," said Willie. "One was the Gorilla.