http://www.sina.com.cn 2007年04月17日 15:06
Most snakes move in a straight line, but there are some notable exceptions.One is the snake called the American sidewinder. From its name, you can probably guess that it moves side ways rather than in a straight line. And this is because it lives in the desert where the sand slips and slides. With nothing firm to push against for traction, the sidewinder has had to adapt its way of movement to the shifting sand. It pushes against the sand with the entire side of its body, and then moves sideways or sidesteps. It lays its body at about 60degree angle to the direction in which it wants to go. By doing this, the snake has more sand to push against. Then it points its head in the direction it wants to go and leaps. An added advantage gained from this method of moving may be that the snake's body is kept cooler by the breaking of contact with the hot sand during its leaps.
Nineteenth-century writers in the United States were powerfully drawn to the railroad in its golden years. In fact, writers responded to the railroads as soon as they began to be built in the 1830's. By the 1850's, the railroad was a major presence in the life of the nation. Most writers saw the railroad both as a benefit to democracy and as an object of suspicion. The railroad could ruin nature. Furthermore, in its manifestation of speed and noise, it might ruin human nature as well. By the 1850's and 1860's, there was a great distrust among writers and intellectuals of the rapid industrialization of which the railroad was a leading force. Some philosophical historians regretted the role that the new passion for business was playing in eroding traditional values. A distrust of industry and business continued among writers throughout the rest of the nineteenth century and into the twentieth.