书城教材教辅科学读本(英文原版)(套装1-6册)
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第156章 第二册(73)

The wild rabbit makes its home in a burrow under the ground. Its blunt, strong claws are its digging tools. It feels its way in these dark tunnels with its whiskers. It comes out into the ?elds, morning and evening, to feed on the farmer"s crops.

Lesson 33

Lead

"I had never thought till today," said Will, "what a useful metal lead is.""Father has lent me these pieces of Lead," said Fred. "Let us have a talk. Suppose we begin with this piece of sheet-lead.

"What does this sheet-lead tell you, Norah?""It tells me that the lead must be malleable, because it has been hammered out into these thin sheets," said Norah.

"Well, if it has not been hammered out, it has been rolled out," said Fred. "The truth is, malleable metals are more often rolled out than beaten flat with hammers. This sheet-lead was rolled flat between heavy steel rollers.

"Sheet-lead is sometimes made in another way. The lead is melted and poured out on a flat table covered with fine sand. While it cools and hardens, it is rolled with wooden rollers.

"Take the piece of sheet-lead, Will, and see how easily you can bend it.