Chuyên đề 8
Narrator: Before you hear the next part of the lecture, you have some time to look at questions 35 to 37. Now, listen and answer questions 35 to 37.
Right now let's have a detailed look at how the bridge was raised for ships to pass through it. This is a slide showing a diagram of the bridge, and here you can see at the far end of the south side of it are the original engine rooms, which you can visit today if you take a tour of the bridge. In here, there was a boiler which was powered by coal. This boiler produced steam, which powered two big engines, and these engines produced pressurized water which was stored in six containers called accumulators. This was sent via pipes to some more accumulators in each of the two piers in the central section of the bridge.
When it was time to open the bridge, the bridge operator, situated at the bottom of the tower on the south side, pulled a set of levers to set in motion the opening of the bascules. This action started engines in each of the two piers, each of them operating one of the two bascules. Gears attached to these two engines, which were called the driving engines, would then turn, causing the bascules to rise and open. The bascules rose to an angle of 86 degrees, providing enough room for ships to get through the central part of the bridge. Although the process was quite complex, it actually took only about a minute for the bascules to rise to their maximum height.