书城教材教辅科学读本(英文原版)(套装1-6册)
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第172章 第二册(89)

"Look now at this very thin silver wire," added Fred. "I pulled it out of an old piece of fringe. What do you learn by looking at the wire, Norah?""I learn," replied his sister, "that silver must be very ductile, or it could not be drawn out into fine wire like this.""Quite right," said Fred. "This silver wire is used for making lace and fringe.

"We said just now that silver does not rust," he went on, "but the fumes of our fires and gas will soon cause silver to tarnish. Sulphur too will quickly tarnish it, and turn it dull and black, like a dirty piece of lead. But a rub with the leather soon cleans it again, and brings back its beautiful white lustre."SUMMARY

Silver is a pure-white metal, with a very high, metallic lustre. It does not rust. It is a precious metal. It is very malleable, ductile, and tenacious. It is made into money, and many beautiful articles for use and ornament.

Lesson 40

Gold

"Come here, Norah, and see how rich I am," said Fred.