| 单词 | Jacob's staff |
| 释义 | Jacob's staff/ˈdʒeɪkəbz /noun A rod with a sliding cursor formerly used for measuring distances and heights.In January 1472 he made observations of a comet, using his Jacob's staff, which were accurate enough to allow it to be identified with Halley's comet 210 years (and three returns of the 70 year period comet) later. Origin |
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