Footnote [24]: “The German word Kette”—had “work.”

Questionable spellings have been retained as follows:

Page [125] and [Index]: J. B. [Johann Bartholomacus] Tromsdorff—should be Johann Bartholomäus Trommsdorff?

Page [129]: “sulphur, phosphorous and carbon”—should be “phosphorus” but may be misspelled in the quoted material?

Footnote [20]: “Sur le Multiplier electro-magnetique”—should be “Multiplicateur”?