3070. ... the time has arrived, when the idea conveyed by [lines of magnetic force] should be stated very clearly, and should also be carefully examined, that it may be ascertained how far it may be truly applied in representing magnetic conditions and phenomena; how far it may be useful in their elucidation; and, also, how far it may assist in leading the mind correctly on to the further conceptions of the physical nature of the force, and the recognition of the possible effects, either new or old, which may be produced by it.
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Published before 1923