Since writing the above, we have been shown, by a professional gentleman, an excellent contrivance for taking altitudes or depressions with the box-sextant, which consists of two small spirit-levels fixed at the back of the horizon-glass, at rightanbsp;...

Title | : | A treatise on the principal mathematical instruments employed in surveying, levelling and astronomy |

Author | : | Frederick Walter Simms |

Publisher | : | - 1834 |

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