题型:阅读理解 题类:常考题 难易度:普通
重庆市第一中学2018-2019学年高二上学期英语期末考试试卷
The horse I'm riding is named Candy, which is appropriate, taking account of her love for eating. As we go our way down the mountain of Big Bend National Park, Texas, I'm sweating—half due to the hot weather, half due to an effort to stay on the horse. Candy, however, is relaxed and stops to eat cactuses (仙人掌) as she passes. She is used to the dusty trails through hills and canyons(大峡谷) and ignores my attempts to guide her away from her delicious food. Our ride becomes a battle of will, which Candy wins easily. I comfort myself by admiring the views across Big Bend's wide open spaces.
Texas only national park, Big Bend, extends across 800,000 acres of the Chihuahuan Desert, in the deep southwest of the state right along the border with Mexico. It is named after the U-turn that the Rio Grande River makes here. It has seen a lot of fights. The Spanish, Anglo-American settles, Mexicans, and Apache and Comanche American Indians all fought to rule this place.
Our group member, Mike, knows every corner of the park and describes it as “sort of a secret place”. Even some Texans don't know about Big Bend, he says. Other local people describe it as a forgotten national park. Compared with the almost five million travellers that descend on the Grand Canyon every year, only 30000 make it here.
There are six of us in the riding group, all fairly inexperienced, led by tour guides, Linda and Janelle, who keep both us and the horses in line. We trek along the top of an 800-foot mountain, with wide-winged eagles flying beside us. The air is noiseless.
The park is fantastic for hikes and has a variety of marked walking paths. The walk is a five-mile round trip. While the final stretch is rather steep, the views over giant canyons and plains are worth the effort.
Hot Air Balloons
| A hot air balloon is made up of 3 main parts:
The Envelope The actual fabric balloon which holds the air.
The Burner The unit which pushes the heat up into the envelope
The Basket Where the passengers and pilot stand |
The basis of how the balloon works is that warmer air rises in cooler air. This is because hot air is lighter than cool air as it has less mass per unit of volume. Mass can be defined by the measure of how much matter something contains. The actual balloon has to be large as it takes a large amount of heated air to lift it off the ground.
The burner uses propane gas to heat up the air in the envelope to move the balloon off the ground and into the air. The pilot must keep firing the burner at regular intervals throughout the flight to ensure that the balloon continues to the stable. Naturally, the hot air will not escape from the hot at the very bottom of the envelop as firstly, hot air rises and secondly, the floating power keeps it moving up.
To move the balloon upwards, the pilot opens up the propane value which lets the propane flow to the burner which in turn frees the flame up into the envelope. It works in much the same way as a gas grill: the more you open the valve, the bigger the flame to beat the air and the faster the balloon rises.
The “Parachute Valve” at the very top of the balloon is what is used to bring the balloon down towards the ground. It is a circle of fabric cut out of the top of the envelop which is controlled by a rope which runs down through the middle of the envelope to the basket. If the pilot wants to bring the balloon down, he or she simply pulls on the rope which will open the valve, letting hot air escape, decreasing the inner air temperature. This cooling of air causes the balloon to slow its rise.
The pilot can operate horizontally by changing the vertical position of the balloon because the wind blows in different directions at different altitudes. If the pilot wants to move in a particular direction, he or she simply arises and falls to the appropriate level and rides with the wind.
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