A Bradley tangent galvanometer is used, employing the coil of 160 ohms resistance.
"Scientific American Supplement, No. 492, June 6, 1885" by Various
The strength of different currents can be compared, and many interesting experiments performed with the tangent galvanometer.
"How Two Boys Made Their Own Electrical Apparatus" by Thomas M. (Thomas Matthew) St. John
In 1849 H. von Helmholtz devised a tangent galvanometer with two coils.
"Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2" by Various