首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Glass is made of mixture of many substances melted together in a large furnace. The most important substance is silica which is
Glass is made of mixture of many substances melted together in a large furnace. The most important substance is silica which is
admin
2014-03-31
32
问题
Glass is made of mixture of many substances melted together in a large furnace. The most important substance is silica which is found in sand. Potash(钾碱), obtained from wood-ashes, is also necessary. To these two substances are added lime, lead, soda and charcoal. Acids are used to remove iron and other impurities. Which might discolor the glass.
The heat of the furnace is so intense that the mixture of these various materials is changed into a boiling liquid. How is liquid glass formed into beautiful or useful objects? Let us imagine that we are watching things being made in a glass factory. It is a small factory in which the work is still done by craftsmen and not by machinery.
Here is a man holding a long iron tube called a blow-pipe. The tube has a wooden mouth-piece to protect the man’s lips from the heat. He puts the other end of the pipe into the molten glass and picks up some of the mixture on the end of the tube. Then he robs the lump of glass to and fro on a metal table, rather like a person rolling pastry. As he rolls it, he shapes the lump roughly into the required form.
Next he lifts the pipe, puts the wooden end to his lips, puffs out his cheeks and blows as you do when you are blowing up a balloon. But of course he has to blow much harder. When the air is blown down into the lump of molten glass a gorge bubble is gradually formed. The craftsman needs both powerful lungs and great skill to ensure that the bubble is of exactly the required size and thickness.
Now you understand why so many hand-made glass objects are round in shape. Handles and feet must be added while the glass is still plastic. When the object is shaped to the craftsman’s satisfaction, it is allowed to cool off. The cooling must be done very gradually. As you know, glass is cracked by extreme and sudden changes of temperature.
Some of the loveliest and many of the most useful things in the world are made of glass. It is most surprising, in view of the great technical skill required, that glass making is a very ancient art. It was practiced thousands of years ago by ancient Egyptians although it was many centuries before men discovered how to make glass transparent.
Glass Making
To remove impurities from the glass,【46】.
Craftsman rolls the molten glass【47】on a metal table.
Glass objects are made【48】.
The mouth-piece of the blow-pipe is【49】.
All glass is【50】.
选项
答案
acids are used
解析
转载请注明原文地址:https://jikaoti.com/ti/de1MFFFM
本试题收录于:
大学英语三级B级题库大学英语三级分类
0
大学英语三级B级
大学英语三级
相关试题推荐
Supposeyouwanttobuyahouse.Itisimportanttolook(11)beforeyoubuyahouse.First,decidehowmanyroomsyouwant
Dearfriends,GoodeveningandwelcometoourannualYearAwardsBanquet.Itissuchapleasuretoseesomanyfriendshere.
Theword"sport"firstmeantsomethingthatpeopledidintheir(11).Lateritoftenmeanthuntingwildanimalsandbirds.Ab
AccordingtothenewfindingsofDr.Kleitman,ifapersonfindsgettingupearlyisdifficult,mostprobably______.Youaread
Themost(11)waytowelcomethenewyearintheUnitedStatesiswithabigparty.Somepartiesareatprivate(12).Buti
______isoftenmoredifficulttofindtrainedmenthantogetfinancialsupportforscientificresearch.
A、Idon’tlikebuttonandbeef.B、Abagoffruitandsomevegetables,please.C、Myfavoritefoodisn’tbreadandbutter.D、Idon
A、Thewomanwilldrivetonight.B、Thewomandoesn’tlikefruit.C、Thewomanhasgivenupsmoking.D、Thewomanisleavingnow.A本
April20th,2005Re:HotelArrangementsforStarwaysLtd.DearMr.Hinson,Iwouldliketoconfirminwritingthearrangement
A、Atthebank.B、Inarestaurant.C、Inahotel.D、Attheairport.C细节推断题。对话中男士说今晚想要一间双人房,女士问他有没有提前预订。因此推断对话应该是发生在旅馆,所以选C。听录音时抓住对
随机试题
R-S细胞(Reed-Sternbergcell)
交叉配血试验中,不能检测出IgG性质的不完全抗体的试验是
患儿,男,3岁。夏季发病,发热1天,无汗,口渴烦躁,2min前突然抽搐。查体:体温40.2℃,舌红,苔黄,脉洪数。辨证为
足三里
职业病危害项目申报应提交的材料有()等。
某输变电工程公司在浙江省经竞标,获得了一500kV的变电站建设项目和20km输电线路的架设项目,设备由浙江省电力公司经国网公司集中采购。在施工过程中发生了一系列问题:其一,在组立铁塔时,因设置缆风绳和铁塔组片,损坏了村民的庄稼和果树,与村民就赔偿问题发生矛
定向广告是指网络服务商利用网络追踪技术搜集、整理用户信息,按年龄、性别、职业、爱好、收入、地域分类储存用户的IP地址,然后利用网络广告配送技术,向不同类别用户发送不同的广告。根据上述定义,下列描述符合定向广告的是:
根据哈威格斯特的观点,中年期的发展任务有()。
J.Martin认为,要提高企业信息系统中数据处理的效率,下列几项中()是最重要的。
A—TheatreArtsB—UrbanStudiesC—StatisticsandProbabilityD—EnvironmentalA
最新回复
(
0
)