That might signal a small patch of blue sky.

这可能标志着天空那一抹蔚蓝色出现。

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Only a tiny patch of blue was visible in the cloudy sky.

多云的天空中只见到一小块儿湛蓝。 。

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Financial analysts see a patch of blue sky should car sales recover.

FORBES: What GM Will Look Like, If It Survives

Find this orientation by looking through the crystal at the sky at a time when you can see the sun, mark the sun's direction on the crystal, and your mark will always point towards the sun when you match the beams from even a tiny patch of blue in an otherwise overcast sky.

ECONOMIST: How Norsemen found their way round in cloudy weather