among miners, the interruption of a vein of ore or stratum. See Mining.

Dipping Needle, a magnetic needle that dips or inclines to the earth; an instrument for ascertaining the amount of the magnetic inclination at the different points of the earth's surface. This fact was first observed by one Robert Norman, an Englishman, and a maker of compasses for mariners, about the year 1576, who finding that he was always obliged to counterbalance that end which turns to the north by a bit of wax or such other substance, though the balance had been ever so exact before, published an account of his dis- covery as a matter of importance. The subject was instantly attended to; and instruments were not only contrived for ascertaining the quantity of the dip, but various speculations were formed concerning the cause of so surprising a phenomenon.

The general phenomena of the dipping needle are, that in the equatorial regions it remains in a horizontal position, but as we recede from the equator towards either pole it dips; the north end if we go northwards, and the south end if we proceed southwards; and the further north or south we go, the greater is the inclination. Its inclination is likewise found to vary very considerably at different times in different places of the earth. See Magnetism.