It was the first bridge in Rome，and when “the dauntless three”stood there with flashing swords and mocked the whole invading army，it was the only bridge in Rome.It was a wooden bridge，one that could be cut down with axes，and it was so important to Rome that it was in charge of priests.We are told that when a new bridge was built，after Horatius and the old bridge had saved the city，the priests themselves built it.
Have you ever heard the Pope spoken of as the Supreme Pontiff？Supreme Pontiff is one of his titles.Would you ever guess that this title of the Pope came from the bridge that Horatius defended？The chief priest in ancient Rome was called the Pontifex Maximus，which in English means the Greatest Bridge Builder.He was called this because he was chief of those in charge of the bridge.So pontifex，or pontiff，came to mean priest，and that is why the Supreme Pontiff or Bridge Builder is one of the Pope’s titles.
The pont part of pontiff turns up in another strange use.Try to imagine what Horatius would have thought if he had suddenly seen a seaplane flying overhead，its propeller roaring，its pontoons glistening in the sun.A pontoon is a kind of boat used to hold up a bridge.A bridge across boats is called a pontoon bridge.And so the pontoons that hold a seaplane upon the water got their name because they are like the boats that hold up a pontoon bridge.
And now I’d better tell you what kinds of bridges there are.There aren’t as many different kinds as you might think.Really there are only five kinds，and that’s a good thing because you can easily learn those five，and then you can name any kind of bridgeyou see.
Here they are：
Number One is the simple beam bridge.A log across a stream is the simplest kind of a simple beam bridge.
Number Two is the arch.A rainbow would make a beautiful arch bridge，if you could only walk across it.The Chinese have some beautiful arch bridges.
Number Three is the suspension bridge.A wild grape-vine stem that hangs from one tree to another is a good suspension bridge—for a monkey.
Number Four has the hardest name to remember.It is the cantilever bridge.If you have a board you can make a cantilever bridge.Hold the board by one end so it just reaches across to the table，but don’t let it rest on the table.Then the board is a cantilever bridge.A cantilever is a simple beam supported at one end，something like a diving board.Often the bridge has a cantilever coming from both banks of a stream and meeting in the middle.
Number Five is the truss bridge.A truss bridge has its beams strengthened by a stiff framework of different parts fastened together.The framework may either rise above the roadway of the bridge or be beneath it.The frame of a bicycle is something like a truss.Cantilever bridges are often built with trusses.Most truss bridges are built of wood or iron or steel.
These are the five kinds of bridges.What about pontoon bridges？Pontoon bridges arejust simple beam bridges with the beams resting on boats instead of on posts or piers.
The earliest bridges were，naturally，beam bridges.Xerxes of Persia，a great king，built a pontoon bridge across the Hellespont when he came to fight the Greeks in 480B.c.
Strange to say，the Greeks，who could build a perfect building like the Parthenon，were not bridge builders.They traveled by boat more than by road and so they needed few bridges.Then too，the rivers of Greece are generally small enough to be crossed without a bridge，though the Greeks probably got their feet wet in crossing.
That brings us back to the Romans，the greatest bridge builders until modern times.All roads led to Rome，and the roads had many bridges.Not only in Italy but in Spain and France，in England and in Austria，the fine Roman bridges helped the traveler to get where he wanted to go.Many of the Roman bridges are still standing，are still in use after two thousand years of service.Some were of wood and of course they disappeared long ago，but most of them were built of stones so well fitted together that often no mortar was needed.
The biggest Roman bridges were not meant to carry people，however.They were bridges to carry water.If you had wanted to take a bath in ancient Greece you would have had to carry the water in jars from the stream or well or else use the stream for a bath tub.But in a Roman city many of the houses had running water and there were also public bath houses where you could bathe in beautiful indoor swimming pools full offresh，clear water.All this water was brought to town by long aqueducts，stone bridges with a trough on top.These aqueducts went across country for miles from the mountain streams to the city.
When an aqueduct came to a valley it didn’t go dipping down into the valley and then up on the other side.It went straight across—as a very high bridge indeed.The Romans couldn’t make water pipes very well and so if the aqueducts had gone down hill and then up again，the water would have spilled out at the bottom of the dip.The bestknown aqueduct is now the famous ruin called the Pont du Gard over the river Gard near N？mes in France.
After the fall of the Roman Empire，bridge building had a fall too.For years and years during the Dark Ages very few bridges were built.Then in the twelfth centuryA.D.a strange thing happened.Bridges throughout Europe went back to the care of priests.Only，the priests this time were Christian priests.They formed a society called the Brothers of the Bridge.