image mo_magnetic field model
Image number: RS.18187
Credit: ©The Royal Society





Ferdinand Engel (fl. 1840s-1860s, German), Instrument maker

Object type

Archive reference number



Content object


Plaster model of a three-dimensional surface, or magnetograph, with months of the year listed down the length and hours of the day along the width. Intended to represent the seasonal changes of Philadelphia's magnetic fields, specifically, the inequality of the horizontal force throughout the year.

Printed inscription on model side: 'Model of the magnetic surface presented in the discussion Part II of the magnetic observations made at the Girard College Philadelphia between 1840 and 1845, by Prof. A.D. Bache. Const. and modeled by Ferdinand Engel, Washington, D.C. 1862.'

Alexander Dallas Bache (1806-1867) American physicist and surveryor was elected a Foreign Member of the Royal Society in 1860. In 1838 Bache was appointed President of Girard College and subsequently made Philadelphia the focus of much of his magnetic data collection and research.

Object history

Exact provenance unknown, however, evidence that the Royal Society was in contact with Alexander Dallas Bache on his terrestrial magnetism research is present in the Society's volumes of correspondence on the same [MS/119/1/99].

Likely a copy of the model made for the Smithsonian Institution, which published Bache's written account of his magnetic observations in 1859. [Alexander Dallas Bache, "Discussion of Magnetic and Meteorological Observations Made at the Girard College Observatory, Philadelphia, from 1840 to 1845," Smithsonian Institution Contributions to Knowledge].

Related Fellows

Alexander Dallas Bache (1806-1867, American), Physicist

Associated place

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