however, a galvanized iron rod conducts as a combination of iron and zinc, in which the zinc possesses a much higher conducting power than the iron. Zinc surpasses iron in this particular at least three times. All the statements of conductivity that have been drawn from galvanized iron conductors have hence been given much too low. The influence of a too powerful electrical discharge upon a conductor of galvanized iron is, in the first instance, to strip off its coating of zinc by melting this more readily fusible metal. But until this is done the zinc assists very materially in the transmission of the discharge. Practically it is known that galvanized iron ropes effectually transmit discharges which could not be safely carried by ungalvanized ropes of the same diameter. The table is on this account worthless for the purpose for which it was avowedly prepared. It attributes to several of the authorities which are named views on the matter of the size of lightning-conductors which they would certainly not indorse. For instance, Mr. Preece, the eminent electrician, is represented as holding that a copper wire with a sectional area of only the one-hundredth part of a square inch is "sufficient to serve as a lightning-rod for any house." The authority upon which this startling statement is made is a passage in the "Journal of the Society of Telegraph Engineers," in which Mr. Preece says that he thinks "galvanized iron wire one quarter of an inch in diameter is sufficient for the protection of any house." It needs no very large amount of acquaintance with electrical matters to enable the reader to understand that Mr. Preece would not himself have expressed the same confidence in a small copper bell-wire such as is given as the equivalent in the table of the report. Taken in connection with the omission of all reference to the increased resistance in long conductors, it might be inferred from this estimate that Mr. Preece would hold a small copper bell-wire, carried from the golden cross of St. Paul's to the ground, to be a sufficient protection for the great metropolitan cathedral.
In his "Notes et Commentaires sur la Question des Paratonnerres," printed in 1882, Professor Melsens complains that no notice of his system of numerous conductors of weak or small section has been taken in the code of laws of the Lightning-Rod Conference of London, even as a possible alternative of construction, a silence which he interprets as equivalent to a formal condemnation. He says:
