The Collaborative International Dictionary
Sideroscope
Sideroscope \Sid"er*o*scope\, n. [Gr. ??? iron + -scope.] An instrument for detecting small quantities of iron in any substance by means of a very delicate combination of magnetic needles.
Wiktionary
sideroscope
n. An instrument for detecting small quantities of iron in any substance by means of a delicate assembly of magnetic needles.