填空题
(11)In the early 1800s a new kind of power changed transportation and trade along the Mississippi River. This power was steam. People already knew how to use steam engines to run machines. Some people want ed to move boats in the same way. The first steamboat to travel on the Mississippi was the "New Orleans". (12)It made its first trip in 1811. It was a great success, and by 1819 there were 191 steamboats traveling on the river.
(13)In the past, the farmers whose products went to other parts of the country used the steamboats. (14)The manufacturers whose trade depended on cheap and easy transportation used the steamboats, too. (15)Today many tourists come to travel on the steamboats, while manufacturers and farmers no longer use them and turn to other ways for transportation. So the application of steam boats has changed now.