(点击右边三个点，可调整速度，电脑上可下载)

听力参考原文 ↓↓↓

Imagine this: It's 1418 in Florence, Italy.

You've been challenged to build a great dome for the Santa Maria del Fiore, one of the grandest cathedrals ever built, and you have no formal architectural training, no pressure, right?

For Filippo Brunelleschi, a goldsmith and clockmaker, it was the opportunity of a lifetime.

He considered the challenge carefully...then proposed a daring plan, using methods that experts don't fully understand even to this day.

At the time, domes were often built as semicircles, but the town fathers required that Brunelleschi build an eight-sided dome that would be even taller and stronger.

It would also have no central support system to hold it up during construction.

Even worse, the dome's base was an imprecise octagon with no true center. But Brunelleschi had that covered.

There would be two domes instead of one: an inner and an outer shell held together by giant brick arches and interlocking rings of stone and wood.

The rings would work like hoops on a barrel, keeping the dome from expanding outward.

To move heavy loads hundreds of feet up, Brunelleschi designed ingenious new machines, including an ox-driven hoist and massive lifting devices far ahead of their time.

So, revolutionary design, check; groundbreaking engineering, check; can-do attitude, check.

But with no central support system, how would he actually build it

First off, the masonry would have to support itself during construction.

To do this, Brunelleschi lays the bricks in a herringbone pattern, which spiraled to the top of the dome,with vertical bricks acting as bookends to hold the others in place.

They laid about one row a week, giving the mortar time to cure.

At this rate, the dome grew at a snail's pace of about a foot a month.

But perhaps most puzzling is how he was able to place the bricks with such precision.

Many experts agree that he used guide ropes.

One theory states that ropes ran from a flower pattern on the work platform that showed exactly where the bricks should go.

Another has ropes running from the dome center, tracing a series of cones that grew smaller as they ascended to the top.

Still another suggests a different arrangement of central ropes and wooden templates.

However it was done, it worked.

The eight phases of the dome met at the top precisely, just as Brunelleschi had planned.

In all, it took 16 years to complete the dome.

When he died in 1446, Brunelleschi left behind no sketches and no details as to exactly how he achieved his masterpiece.

Today, it remains the largest masonry dome in the world, more than 500 years after it was built.

本文来自公众微信号：练英语听力