1.If you had lived in Britain a thousand years ago，you might have seen panes of glass in the churches，but you would have found very few glass windows in the houses of the people.The windows in those days were generally narrow open slits in the wall，though sometimes they were filled up with thin pieces of horn，or with thin skin.
2.What a difference glass windows have made in the brightness and comfort of our homes ！The glass is so transparent that it lets the light from the sun pass through it，and yet it keeps out both the rain and the wind.
3.Glass is so hard that you cannot cut it or even scratch it with a common steel knife.The beautiful gem called the diamond is，however，even harder than glass；and glaziers①use small diamondsset in a handle to cut glass to the size that they want.Little wheels of extremely hard steel are also used for cutting glass，and this they do fairly well，though not nearly so well as diamonds.
4.If you hold a pane of thin glass under water，you will find that you can cut it with a pair of scissors.But you must cut near①Glaziers，men who put glass in windows.
the edge of the glass，and take off only a little bit at a time.Like many other hard substances，glass is very brittle-that is，it will snap easily if we try to bend it，or if we let it fall.
5.Glass is made chiefly of fine white sand or silica melted in a furnace.To make the sand melt easily，we must mix with it some soda，some chalk or lime，and a small quantity of broken glass.
GLASS-MELTING POTS AND FURNACE（玻璃坩埚及熔炉）6.Have you ever seen a glass-house，or a building in which glass is made ？It is generally built of bricks，in the shape of a large cone①.The mixture of sand andsoda is put into large melting-pots，and these are placed in the furnace or fierce fire which burns in the centre of the glass-house.
7.Soon the mixture melts and forms a white-hot liquid.To make plate-glass②，this liquid is pouredupon an iron table，and then rolled out just like dough with iron rollers.The hot sheet of glass is then placed in①Cone，a figure with a round base or bottom tapering to the top，like a sugar-loaf.
②Plate-glass，a fine kind of glass，cast in plates，used for looking-glasses，etc.
a room，where it cools very slowly indeed.This is called annealing：If the glass were cooled quickly，it would be too brittle to use.
8.Cheaper and thinner kinds of window-glass are made by blowing.The glass-blower dips a long iron tube or blow-pipe into the melted glass，taking up a little of it on the end of the tube.He then blows this out like a huge soap-bubble，and as it begins to cool he rolls the glass -bubble on a smooth table until it becomesa cylinder①.This cylinder is afterwards cut open with a diamond，and is spread out into a flat sheet after it has again been softenedby heat.
SUMMARY
Glass is made by mixing fine white sand with soda，lime，and broken glass.The mixture is melted in a very hot furnace in the glass-house and poured upon iron tables，rolled with iron rollers，and then left to anneal or cool.The glass thus formed is plate-glass.Cheaper window-glass is made by blowing the melted glass，and rolling it till it becomes a cylinder.This is then cut①Cylinder，a body shaped like a roller.
open and spread out into a flat sheet.Glass is transparent，and lets in light while it keeps out both wind and rain.Glass is very hard and very brittle.It is generally cut by a diamond or a small wheel of very hard steel.
【中文阅读】
1．穿越时空，回到一千年前的英国，就会发现，只有教堂可能会使用窗格玻璃①，而平常人家几乎很少有人使用玻璃窗户。那时候的窗户实际上就是墙面上的一个狭窄开口而已，有时候装上牛羊角的薄层或者轻薄的兽皮。
2．玻璃窗改变了我们的家庭生活，带来了不同凡响的明亮与舒适感受！玻璃的透明度极高，可以允许阳光轻松穿过，将风雨阻隔在外。
3．玻璃的硬度很高，普通的钢制刀具无法对它进行切割，甚至都不能在它的表面留下划痕。然而，那种被称作金刚石的美丽宝石比玻璃更加坚硬；玻璃工人使用一把带有手柄的金刚石切割工具将玻璃切割为需要的大小。人们还使用极为坚硬的钢轮对玻璃进行切割，这种方法虽然比不上使用金刚石那样理想，但效果还算不错。
4．如果你将很薄的一片玻璃放在水中，就可以用剪刀来进行切割。不过你只能从玻璃的边缘入手，而且一次只能剪下一点点。与其他坚硬的物质一样，玻璃非常脆弱--也就是说，如果你想要弯折它，或者将它从高处丢下，它就会破裂为碎片②。
5．玻璃主要由细致的白沙或硅石在熔炉中炼成。为了确保能够轻松地将沙子融化掉，我们必须要加入一些苏打、白垩或石灰以及少量玻璃渣。
6．你有没有见过玻璃工厂，也就是生产制作玻璃的地方？这样的工厂一般由砖块搭建而成，呈巨大的圆锥形。沙子与苏打的混合物被放入到一个庞大的熔炉中，然后通过工厂中央炙热的炉火进行加热。
7．很快，混合物便被融化并形成白色的沸腾液体。如果要制造平板玻璃，这些液体将被倒在一个铁板之上，然后使用铁制滚子像和面那样反复卷压。随后，人们将滚烫的玻璃片放在一间厂房中，让它们慢慢冷却。这个步骤叫做退火。如果玻璃冷却过快，就会非常脆弱而根本无法使用。
8．更薄、更便宜的窗户玻璃通过吹制而成。吹玻璃工人将长长的铁管或吹管放入融化的玻璃之中，用管子的末端沾上一点。然后，他就开始用力吹，很快，融化的玻璃就会像巨大的肥皂泡一样膨胀起来。等它开始冷却的时候，工人将这个玻璃泡放在平滑的桌子上反复滚动，最后形成一个圆筒。随后，工人用金刚石把这个玻璃圆筒切开。接着，经过再一次加热后，玻璃就会变软，最后变成一块平整的玻璃片③。
译注
①有一个流传很广的说法”凝固的玻璃也会流动“，证据是老房子上的玻璃，有的下面比上面厚。这其实是一种误解，玻璃的主要成分二氧化硅是一种岩石，凝固之后就不会变形了。想让它在重力作用下发生明显变形，需要至少上千万年的时间。老房子装的玻璃，因为加工工艺的原因，薄厚经常不均匀；而装到窗户上的时候，工人为了装得稳当，肯定会把厚的一边装在下面，于是就催生出了这种错误的说法，甚至还被俄国的雅科夫·别莱利曼（Yakov Perelman）等著名的科普作家写进了书中。
②水中剪玻璃的原理是：当水分子进入玻璃的裂缝时，裂缝中的硅氧键和水中的氢氧键会解体，让两个羟基团和硅相连，这样裂缝的长度就会增加一个断键那么长的尺寸。水引发的反应，让人可以用更小的能量来打破硅氧键，因此玻璃也就更容易破碎了。但这样剪下来的玻璃不会是很均匀的。
③这两种传统加工方法叫”卷压法“和”吹制法“，但这两种办法制造出来的玻璃都不平。现代玻璃大部分是用”浮法“生产的，把熔化的玻璃原料--硅砂和碳酸钠、碳酸钙等物质浮在液态锡上，经过退火，冷却形成，这样的玻璃厚度就会十分均匀。
ONLY A WEED
蒲公英
Ⅰ
1.All through the summer，and during spring and autumn as well，our meadows and waste places are thickly dotted with the bright-yellow flowers of the common weed called the dandelion.And even throughout the winter the leaves of this hardy①plant remain green.Let us dig up a dandelion，root and all，and examine it；for though it is only a weed，we can learn from it many things about the life of plants.
2.The root is long，thick，and tapering②，and it has many small fibres or rootlets growing from its sides and from the end.The root of a plant，as you already know，fixes the plant in the ground，and its fibres suck in food for the plantROOT（根）out of the soil.But the root of the dandelion does more than this：it stores up in its thick part much food for the use of the plant，to help it in producing its flowers and seeds.
3.The dandelion has no long stem or trunk，but from the top of the root a number of green leaves spread out and form a①Hardy，strong；able to bear all kinds of weather.
