An excellent question I think a good answer will requiring making a correction to the page Schiffer s book says that he Schiffer reformulated Barlow s law to state that the current strength varies inversely with the square of the length of the wire I don t see how to reconcile this with the direct quotations of Barlow s law that are found in other places like the Report on Mining etc I m guessing that the answer has something to do with Barlow s terminology which we should explain in the article Barlow s law could not have been about conductance or resistance in the modern sense of the word because that concept wasn t established until Ohm s law