Dipping-needle sentence example

dipping-needle
  • Gilbert in 1600, that the earth itself is a great magnet, having its poles at the two places where the dipping needle is vertical.
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  • Attached to the cross-arm which carries the microscopes used to observe the ends of the dipping needle is a clamp, which will hold the needle b in such a way that its plane is parallel to the vertical circle and its axis is at right angles to the line joining the two microscopes.
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  • Hence, when the microscopes are adjusted so as to coincide with the points of the dipping needle a, the axes of the two needles must be at right angles.
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  • This seems in general to be nearly coincident with the direction of the dipping needle.
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