有句俗语是这样说的，“需要是发明之母”。意思是说，如果你需要的东西暂时还没有，你就要发明某种东西来替代。正是需求使得亚述人发明了一种最重要的建筑方式，沿用至今。这种建筑方式叫做拱形原则。
亚述人找不到足够长的石头来为大房间做延展宽阔的天花板，他们就发明了一种方法，用小石块或砖块来做房间的天花板或门道。也许你会把宽敞的门道称作拱门，但是把一块砖或一根木横放在道口并不形成拱门——必须有好几块才能建成。
然而，要把小石块或砖块牢牢地粘放在一起，形成一个整体，以保证拱顶能从墙的一边伸展到另一边而不掉下来，是不可能办到的。
但如果将这些石块以某种方式排放，它们就不会掉下来。这种方式就是，将这些石块摆成弧形或半圆状，就形成了“拱顶”。
通过这种简单的排放，石块就会牢牢地待在一处，不是因为它们被粘在一起，其实它们之间无论涂没涂粘土，它们都不会掉下来，那是因为每一个石块一边在往下挤压，一边又在相互挤压，一个挤一个，紧紧挤在一起，没有哪块能挤出来往下掉。只要不让石块把边墙推倒，不使空间扩展，拱门顶上的石块受力越大，稳固性反而越强。
试试把半打书并列在一起，并用双手挤压。如果你挤压的力度足够的话，它们就不会滑落下来，但只要一松手，它们就会全倒下。所以，为了阻止石块掉落，拱门两侧的边墙都必须建得既结实又厚实。
不仅仅是门道，所有的房间都可以用这种方式来做房顶。当一间房屋作了这样的拱顶，就叫做“圆筒形拱穹”，因为房屋的拱顶看起来像个半截木桶。如果房间四周的墙壁也是半圆形，那么整个房间看起来就像是一个倒扣过来的碗。我们把碗状的屋顶称作“圆顶”，但遵循的原则是一样的——即“拱形理论”。
在建造拱顶或圆顶时，一定要在顶端的石块下面再放些什么作支撑。因为只有当最后一块石头到位了，整个拱门才不会坍塌。通常情况下，得用木头临时搭个看起来像半圆的支架，也称“拱鹰架”，拱门就建造在其上。工程从两边开始，一直往上。最后砌到顶端的那块石头叫“拱心石”。只有当“拱心石”安放好了，才能撤走拱鹰架，使拱门独立，不至于坍塌。而在亚述，缺乏做拱鹰架的木材，所以拱门或拱顶比较罕见，直到一千多年后拱形建筑才得以普及。
在埃及，金字塔依然伫立，因为它们是石砌建筑，而且建筑方式也是目前最牢固的一种。它既不会坍塌，更不会倾倒。而两河流域的国家现在一座现存的宫殿或神庙也没有了。当时用的泥砖已化作尘土，只剩下长满野草的土墩了。
说起来可能有点令人难以置信。现在的城市在多年之后也会像古代亚述或巴比伦那样，化作一堆堆长满野草的土丘。来来往往，熙熙攘攘的人群也终将消失不见。当年生活在亚述的人也可能早就料到了这一点。
THE PERFECT BUILDING
完美的建筑
IF YOU make a mistake in your arithmetic or composition，you can correct it or tear it up and do it over.If a picture or a statue is ugly，it can be put out of sight，hidden，or destroyed.But if a building is ugly，there it stands for every one to see.Its ugliness，its mistakes cannot be covered up until it falls down or is torn down.An architect once committed suicide just as the great temple he had planned was finished.He left a note saying that he had made five mistakes in the building and as they could not be corrected and could not be covered up，there they were for every one to see forever.He could not stand the disgrace.
Most buildings that are erected have many mistakes，many things that are ugly about them，though few people，few passers-by may notice anything wrong.
But there was one building that was erected over two thousand years ago that has no mistakes.It is one of the few perfect buildings in the world.It was built by men，but built for a woman，in honor of a Greek goddess，the Goddess of Wisdom，whose name was Athene Parthenos.And so the building was called after her last name，the Parthenon.It is on a high hill in the city of Athens，in Greece，and though it has been partly destroyed，people go from all over the world to see what a perfect building looks like.
The Egyptian temples had flat roofs because there was little or no rain in Egypt and so a sloping roof to shed the rain was not necessary.The Greek temples had to have slanting roofs，for Greece had rain.So the Parthenon had a sloping roof.
The Egyptians built their temples with the columns on the inside.The Greeks turned the Egyptian temple inside out and put the columns on the outside.The Greek temple was not to hold people，but only the statue of the goddess.People didn’t go inside to worship as they do in our churches.They stood on the outside.The columns the Greeks used were not like those the Egyptians used.They were simpler，but much more beautiful.
Greek temples had three kinds of columns，but the kind used in the Parthenon was the Man’s Style column.It is called Doric after a very old Greek tribe.Not only the column but the style of building that always went with this particular column was strong，simple，plain.That’s why it is called the Man’s Style.There were many Doric buildings in Greece，but the Parthenon was the most beautiful of all.
No.63-1THE PARTHENON，ATHENS（雅典帕台农神庙）A Doric building is built on a terraced or stepped platform and is not made of mud bricks plated with alabaster or tile as the Two River people built their temples，but of solid stone，usually marble.There was no cheating in Greek building.It was really what it seemed to he.
Styles in ladies’hats and clothes change often，as you know，but the Doric style of building has lasted over two thousand years and we are still using it to-day.I’ll try to describe it so you can tell it when you see it.
The Doric column has no base，but rests directly on the platform It tapers slightly as a tree trunk does.Its sides are not perfectly straight.They may look so，but as a matter of fact，they bulge slightly.This bulge is called entasis and a column was given entasis because one that had straight sides，one without entasis，looked as if it were thinner in the middle.
Some architects of the present time，noticing this ever so slight bulge in the Doric column，have thought they would improve on it by making the bulge greater.Some people，when the doctor says take one pill，take two，reasoning that if one pill is good for you，two will be better.But the Greek entasis was just exactly enough and more entasis makes a column look fat and ugly like a man who is fat around the middle.
The sides of the Doric column were then fluted—that is cut with grooves so as to make slender，lengthwise shadows from top to bottom of the column and thus take awayfrom the plainness that a perfectly smooth colunm would have.Most columns nowadays have no fluting.You can imagine how difficult it is to cut such channels in marble without making a single slip.One single slip would ruin the column and it couldn’t be repaired.
The top of the column is called the capital because capital means head.The capital was made of a piece shaped like a saucer，above which was a thin square block.You’ll have to look at the picture to understand the rest.
There is probably some Doric building where you live，for as I have said we are still using this style to-day.It may be a bank or a library，a court-house or some other building.Examine it and see if it has all these things that a perfect Doric building has and only these things.
Are the columns of stone or only of wood？
Are they fluted or only plain？