[03:35.71]13. How much did it cost to complete construction of the Golden Gate Bridge?
[03:41.22]Passage Two
[03:42.77]Mans first real invention
[03:44.73]and one of the most important inventions in history,was the wheel
[03:48.96]All transportation and every machine in the world depend on it.
[03:53.21]The wheel is the simplest yet perhaps the most remarkable of all invention
[03:58.41]Because there are no wheels in nature--no living things was ever created with wheel
[04:04.29]How,then,did man come to invent the wheel?
[04:07.29]Perhaps some early hunters found that they could roll the body on
[04:10.74]a heavy animal through the forest on logs more easily than they could carry it.
[04:16.39]However,the logs themselves weighed a lost
[04:19.89]It must have taken a great prehistoric thinker to imagine two thin slices on
[04:25.14]log connected at their centers by a strong stick
[04:24.14]This would roll along just as the logs did
[04:27.32]yet be much lighter and easier to handle.
[04:30.07]Thus the wheel and axle came into being
[04:32.81]and with them the first carts.
[04:35.29]14. Why was it remarkable of man to invent the wheel?
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