SignedOn base: HARTMANN & BRAUN / Frankfurt A/M. HARTMANN & BRAUN in Cursive, Frankfurt A/M in Italics.
FunctionMagnetic intensity measurements. For determining variations of horizontal magnetic intensity to 1/100 percent.
Variometers are designed to detect changes in the magnetic field. The magnetic field acting on the mirror is set in a way to maximize the effects of a change in the observed magnetic field of the earth. Any changes are then observed by deviations from this reference. The measurements are made by observing the scale through the scope as it is reflected on the mirror.
From the instrument card:
"The four deflection magnets act on a polished plane steel mirror, which is not affected by the variation of declination, as it is deflected at right angles to the meridian."
ProvenanceFrom the Physics Department, Harvard University. Blue triangle indicates use in Physics 3 in the late 1920's.
Related WorksFor method of observation see:
- Wiedermann's Annalen Vol. XV, p.540, and also
- D.C. Miller "Laboratory Physics" p366. (from W. & L. E. Gurley N.Y. Catalogue (1908) p.32.