我们总是发现这亮的部分是面向着太阳的、面背着太阳的那一部分看起来就黑暗。
At other times only part of it appears bright , and we always find that this is the part which faces towards the sun, while the part facing away from the sun appears dark.
最上面比较暗的冰层是去年冬天的雪，而中间比较亮的部分形成于去年夏天，最底部比较暗的部分又是更早一年冬天的雪。
The uppermost dimmer layer is snow from last winter, the bright layer in the center is last summer, and the dimmer layer at bottom is the winter before that.
到现在(787页)，您的眼前可能会一亮，但是这部分内容只是一些简短的技巧，而不是连贯的介绍。
By now (page 787) your eyes might be glazed over, but the material is just short tips rather than any coherent narrative.
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