Tower Bridge is a bascule bridge in London, over the River Thames. It is close to the Tower of London, which gives it its name. It is sometimes incorrectly referred to as London Bridge, which is the next bridge upstream(在上游). It is one of five London bridges now owned and maintained by the Bridge House Estates.

In the second half of the nineteenth century, increased commercial(贸易的) development in the East End of London led to a requirement for a new river crossing downstream of London Bridge. A Special Bridge or Subway Committee was formed in 1876 to find a solution to the river crossing problem. It opened the design of the crossing to public competition. Over 50 designs were received. The judgment of the designs was surrounded by argument, and it wasn’t until 1884 that a design sent by Horace Jones was sanctioned.

Construction of the bridge started in 1886 and took about 8 years’ hard work of 432 construction workers. Over 70,000 tons of concrete were sunk into the river bed to support the construction. Over 11,000 tons of steel provided the framework(框架) for the towers and walkways. Horace Jones died in 1887, and another engineer took over the project. The bridge was opened in 1894.

The bridge sits almost directly above the Tower Subway, the world’s first underground tube railway (1870), which, until the bridge was opened, was the shortest way to cross the River Thames. A computer system was installed(安装) in 2000 to control the raising and lowering of the bascule. However, this has proved less reliable than expected, resulting in the bridge being stuck in the open or closed position on a number of occasions.

Scientists have discovered a bit of hand-made string (线绳) that’s around 50,000 years old in Neanderthal remains. The first Neanderthal remains were found in the Neander Valley in Germany, which is where the name comes from. Neanderthals may have lived mainly in caves and made stone tools, but recent discoveries have given hints that Neanderthals developed some advanced skills that people used to think impossible. For example, Neanderthals knew how to make glue from the bark (树皮) of a tree.

Now, scientists report they’ve found a piece of string on a stone tool made by Neanderthals. Before this, the oldest known piece of string was one made by humans about 19,000 years ago. The string is about a quarter of an inch long. Almost all things made from plants during that time have broken down and disappeared, so it’s very special to find this bit of string.

The scientists don’t know whether the string was attached to the tool. But that doesn’t interest them as much as the fact that Neanderthals knew how to make string. Bruce Hardy, the lead scientist on the project, says that knowing how to make string was meaningful for humans. “We wouldn’t really be here today without that technology,” he says.

Making string is a very arduous process. This string was made from the inside bark of an evergreen tree. To make string that is strong enough, the string must be made of several smaller fibers twisted (缠绕) together in a special way. For the Neanderthal string, several fibers needed to be twisted together into something like yarn. Then three pieces of yam needed to be twisted together in the opposite direction to make the final string.

The scientists Aren’t sure what the string was used for, but they say that string like. the bit that was found could be used to make bags, baskets, traps, or other things. The researchers also suggest that because Neanderthals needed to make pairs and count fibers to make the string, the bit of string may also tell us something about the kinds of math that Neanderthals could do.