Compass, Brunton

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Item Compass, Brunton
Item code
Description Part of Wilson Magnetometer #53
Manufacturer K&E
Donor Elwin Peacock
Location Houston Geoscience Center
Serial number 43765
Taxonomy GSH710

Wislon Magnetometer consists primarily of an auxiliary magnet arm that attaches to a Brunton Pocket Transit (Compass) and a magnet holder that moves along the arm by means of an adjustable rack and pinion. The quantity measured is the absolute horizontal intensity of the earth's magnetic field with sufficient accuracy for gross regional surveys. The advantages are low cost, portability, ease of calculation and simplicity of operation. The instrument may be used on a plane table or mounted on a tripod. In operation, the device is set up with the compass clamped in its holder, leveled, and rotated until the compass needle is aligned with the North index of the compass holder. The auxiliary magnet is then placed in its holder with the south-seeking pole toward the compass; the magnet is moved along the arm by the rack and pinion until the compass needle is exactly at the 30 degree mark on its holder. The distance of separation noted on the scale of the auxiliary arm may be read and used for rapid calculation of the horizontal magnetic intensity.