How the Grand Canyon (大峡谷) was created remains one of the geology's greatest mysteries. Some evidence suggests that the process was a gradual one in which the Colorado River (which runs through the canyon) slowly cut deeper and deeper into the ground over millions of years. But volcanic rock samples taken from the canyon now suggest that the canyon was down-cut instead.

    Down-cutting is when a flood of water rushes over a landscape (地形) with enough force to cut deeply into the ground and leaves behind a canyon. Such a flood is usually released when a natural or man-made dam (堤坝) bursts.

    Robert Webb, a research geologist, says natural dams seem to have formed and broken across the Colorado River several times during the last million years. The dams were built when lava(熔岩) from the eruptions of nearby volcanoes flowed into the river. The lava hardened into hard rocks and blocked the river, causing it to back up and form a lake. Each time the lake grew so huge that it broke the rock dam, releasing a flash flood that furthered the down-cutting process and deepened the canyon.

    Down-cutting is not just an earthly event. Satellite photos sent back from Mars suggest that the process has happened there, too, say many other researchers.

    The photos, taken by the Mars Global Surveyor, indicate that an enormous lake existed on Mars 3.5 billion years ago. The lake spilled into a large nearby hole. One edge of the hole broke, releasing a flash flood that quickly carved out a grand canyon.

    The existence of down-cutting on Mars is just one more piece of evidence that the cold, dry planet was once warm and wet.

    Starting Cycling

    We have two services designed to give people the confidence and knowledge to cycle successfully.

    Lessons

    All our instructors have been trained to National Standards level of “Bike-ability”. This means you will be trained to a standard consistent across the whole country.

    There are 3 levels of skills to progress through. Children would start with levels 1 & 2, progressing from the playground or park to cycle on less busy local roads. Teenager and adult beginners can also learn levels 1 & 2 in an off-road and quiet environment.

    Confident teenagers and adults can broaden their skills by learning level 3, using multi-lane roads and larger roundabouts. We provide both a complete package of lessons for the beginner or individual lessons tailored to the client. Whatever the need we can address and practice until perfect!

    Cost is ￡30 per hour.

    Guided Ride

    We know that riding on the roads in London can be scary, and if you have to navigate (确定行车路线) as well it can become a real hard task! The Guided Ride service takes all the stress out of it for you by providing the following:

    Route planned in advance to suit your skill level. Route map provided to you.

    Cycle and equipment checked. We will teach you a simple method to check basic roadworthiness (车辆性能) of your bike that you can perform on a weekly basis.

    Route discussed and focus given to any areas requiring special attention.

Cycle along with the instructor close behind. Here the traffic can be controlled by the instructor and rider observed.

    We currently cover London Zones 1 & 2. Please contact us if your requirements are outside of these areas.

    Cost ￡30 per hour.

    I grew up in New York my whole life. I studied in a perfect college that happened only to be an hour away from home. Then, about three weeks before the spring term was over, my parents told me we were moving to Arizona that summer. They asked me if I was going to transfer (转学) to another college. I said no. I was not going to change everything in my life at one time and I loved my college and all the amazing things I was doing there. It was my second home; I would not leave everything I knew at the same time since that was asking for trouble.

    I never imagined it would be this hard but, at the same time, the best thing that could have happened to me.

    When out in Arizona, life was hard. I didn't know anyone other than my family and friends. I couldn't bear the extreme heat. But it has helped me so much. I have started working on my writing. I also have time to work out in the gym. It has helped me realize that no matter where you are or who you know you can always find something that you enjoy.

    When back at school in New York, it was hard as well. Living close to home was my security blanket. If something was wrong I could get in my car and drive home and see my family. After my family moved to another city, I lacked security and was always controlled by anxiety. However, it helped me learn independence and forced me to be brave.

    I' m so thankful that I didn't transfer to a different school, which has given me the opportunity to go back and see best friends in my hometown. A year ago, I officially left my hometown for good. It has helped me grow and I am so thankful that I have had this experience. Now, when I graduate from college, I can go anywhere I want. I am no longer afraid to go out on my own into the world. The world is full of opportunities and pleasure and I can't wait to see where I will be next.

    "Make way, good people, make way, in the King's name! "cried he. "Open a text; and, I promise you, Mistress Prynne shall be set where man, woman, and child, may have a fair sight of her brave clothing, from this time till an hour past noon. A blessing on the moral Colony of the Massachusetts, where immorality is dragged out into the sunshine! Come along, Madam Hester, and show your scarlet （鲜红色的；罪孽深重的）letter in the market-place!

    A lane was at once opened through the crowd. Led by the beadle （狱吏），and attended by an irregular procession of serious-looking men and unkind-looking women, Hester Prynne set forth towards the place appointed for her punishment. A crowd of eager and curious schoolboys, understanding little of the matter in hand, except that it gave them a half-holiday, ran before her progress, turning their heads continually to stare into her face, and at the winking baby in her arms, and at the shameful letter on her breast.

    It was no great distance, in those days, from the prison-door to the market-place. Measured by the prisoner's experience, however, it might be considered to be a rather long journey; for, though her manner was proud, she perhaps underwent an extreme pain from every footstep of those who thronged to see her, as if her heart had been thrown into the street for them all to step upon. In our nature, however, there is a condition that the sufferer should never know the intensity of what he endures by its present suffering, but chiefly by the pain that rankles （使痛心）after it. With almost a calm manner, therefore, Hester Prynne passed through this portion of her suffering, and came to a sort of scaffold （刑台），at the western end of the market-place. It stood nearly beneath the eaves of Boston's earliest church, and appeared to be a fixture there.

    Crossing your legs is an extremely common habit; most people don't even notice that they're doing it when they sit down. While you may find it comfortable to sit with one knee crossed over the other, it might be causing health problems that you are not aware of.

    A study published in Blood Pressure Monitoring stated that sitting with your legs crossed can increase your blood pressure. The reason for this is that the blood in your legs has to work against gravity to be pumped back to your heart and that crossing one leg over the other increases resistance(阻力), making it even harder for the blood to circulate. This causes your body to increase your blood pressure to push the blood back to the heart. You won't feel any immediate effects, but repeated, drawn­out increases in blood pressure can cause long­term health problems. So, planning to sit for a long period of time? Don't keep your legs crossed.

    Crossing your legs at the knee can also cause pressure on the major nerve in your leg that passes just below your knee and along the outside of your leg, explains Richard Graves, a medical expert. This pressure can cause numbness and temporary paralysis (麻痹) of some of the muscles in your foot and leg, preventing you from being able to raise your ankle—what we know as that "pins and needles" sensation. While the feeling of discomfort may only last a minute or two, repeatedly crossing your legs until they feel numb can cause permanent nerve damage.

    So next time you sit down, try to get yourself in the habit of sitting with both of your feet on the floor. Not only will it help your posture and stability, but it will also save your health in the long run.

The Chinese Tang Dynasty poet Du Fu is often called the sage(圣人) of poetry. Unlike Li Bai, this poet wrote in various styles, and his works were often innovative(创新的) in language and subject matter. His poems were also filled with meaning. 

His innovation was not at all welcome. The readers of his time rarely showed much appreciation of his original and innovative works. The masses in fact hated and scolded them. Like many artists, Du Fu was only recognised for his genius long after his death. 

Du Fu was born in Luoyang, Henan Province. Although he came from an influential literary family, his early attempts to gain a position in the government by way of the exam system failed repeatedly. He was 43 years old when he finally managed to hold an official position. This was the time when Emperor Xuanzong was attracted to the beautiful Yang Yuhuan and made her his concubine(妃子), which Du Fu severely criticised in his Song of the Beautiful Ladies. 

As the emperor got distracted from important government affairs, some military leaders were becoming too powerful. Du Fu took office in 755, and in the same year a rebel(叛乱) leader An Lushan led his army into the capital of Tang Dynasty. The emperor fled to the west and left the governing of the state to his son. Du Fu and his family took the road north to escape the rebels. 

The poet left his family and tried to get to the headquarters of the new emperor, but he was caught and held prisoner by the rebels in Chang'an. After order was restored again, Du Fu got back his position in the capital. However, he did not enjoy the favour of the new emperor and was given a minor provincial post. In 759 he finally left this disgraceful position and spent the rest of his life wandering around the country.