A device invented by the Abbé Fortin (ca. 1864) consisting
of a piece of paper cut to the shape of a compass needle and
considered to indicate some kind of electromagnetic force. It
was suspended in a glass cylinder by a silk fiber. If the cylinder
was approached by a hand, the paper (over a dial of 360 degrees)
would either turn toward the hand or away from it.
Carried out in a more substantial form with a ‘‘metallic multiplicator,’’
a condenser, and a needle, the magnetometer was
used for the study of terrestrial magnetism to solve meteorological
problems. Since the beginning of the twentieth century, it
has been used for dowsing. (See also Biometer of Baraduc; De
Tromelin Cylinder; water witching)