XVI. Preliminary research on the magnetism developed in iron bars by electrical currents

The author had, many years ago, found that the magnetism developed by electro-magnetic coils in bars of upward of 1/3rd of an inch diameter, was nearly proportional to the strength of the current and the length of the wire, any alteration, within certain limits, of the diameter of a bar being attended with only trifling effects, so long as the point of saturation was not nearly approached. The Russian philosophers Lenz and Jacobi had, however, stated that the magnetism developed was,cæteris paribus , proportional to the diameter of the bar. The discrepancy between the above results is considered by the author to be owing rather to the different circumstances under which the experiments were tried than to any inaccuracies in the experiments themselves.