In 1890 some experiments in which a coil was used were made by du Bois (Phil.
In the magnetic balance of du Bois (Magnetic Circuit, p. 346) the uncertainty arising from the presence of a joint is avoided, the force measured being that exerted between two pieces of iron separated from each other by a narrow air-gap of known width.
For the practical measurement of field intensity du Bois has used plates of the densest Jena flint glass.
An excellent summary regarding the magnetic properties of matter, with many tables and references, has been compiled by du Bois (Report to the Congres Int.
Doubtless the coureurs du bois who at this time began to frequent the Wisconsin forests, touched at the bay many times within the succeeding years as the place was known to be a favourite rendezvous of the Fox (or Outagamie) Indians.