From this time, lightning-conductors came into almost universal use, and their value was not long in being generally recognized. Curiously enough, France, which had been ahead of all other countries in the study of electricity, was not one of the earliest to go in for lightning-conductors. There were, indeed, signs of strong hostility to their introduction. It was held even that they went against the designs of Providence. In 1766, the Abbé Poncelet, in his work entitled "La Nature dans la formation du tonnerre et la reproduction des êtres vivants," in which he sets out to demonstrate that the force which produces lightning is the same as that which causes the earth to fructify, makes a strong protest against the construction of lightning-conductors. In 1782, nevertheless, at the reiterated request of Le Roi, a member of the Academie des Sciences, and friend and admirer of Franklin, the Louvre was endowed with the first lightning-conductor put up on a public building in France. Soon afterwards they became common. In 1784 the Academie des Sciences drew up the first set of rules for the construction of lightning-conductors. It was revised and corrected in 1823, in accordance with the various improvements that had been introduced up till then, and it has been further added to in 1854, 1867, and 1903. These instructions point out that the most important metallic portions of the building should be placed in communication with the conductor, and this should sink into a well. Conductors that are not perfectly constructed are a source of danger, instead of being a protection, for the electric current is apt, instead of running down into the earth, to make for any kind of metallic substance, and cause great havoc. The conductor ought really to communicate with a large body of water--a body of water of greater extent than the storm cloud from which the lightning comes. When the flow is insufficient, the water itself is apt to become electrically charged. It is dangerous to bury the conductor in merely damp soil; first, because one generally does not know whether there is enough of this soil; secondly, because one cannot be sure that the humidity will be sufficient at times of great drought--the very times when storms are most to be feared. Failing a river or great pond, the conductor should be put into wells issuing or having their source in inexhaustible supplies of water deep down in the soil. In his table of statistics showing the number of cases in which lightning has struck either lightning-conductors, or buildings, or ships furnished with conductors, Quebelet gives a hundred and sixty-eight cases in which the conductor has been struck, and in only twenty-seven instances of these (one-sixth of the whole) have the conductors, from some grave flaw in their construction, failed to fulfil their office. These results are the best proof possible of the efficacy of conductors, and the best answer to those who decry them.