Page:Popular Science Monthly Volume 25.djvu/696

680 garden. The rod was finished at the top by a sharp point of bronzed steel, and it terminated at the bottom, five feet above the ground, in a smaller horizontal rod, which ran to a table in a kind of sentry-box, furnished with electrical apparatus. On May 10th, when M. Dalibard was himself absent in Paris, the apparatus having been left temporarily in the charge of an old dragoon named Coiffier, a violent storm drifted over the place, and the old dragoon, who was duly instructed for the emergency, went into the sentry-box and presented a metal key, partly covered with silk, to the termination of the rod, and saw a stream of fire burst forth between the rod and the key. The old man sent for the Prior of Marly, who dwelt close by, to witness and confirm his observation, and then started on horseback to Paris, to carry to his master the news of what had occurred. Three days afterward, that is, on May 13, 1752, M. Dalibard communicated his own account of the incident to a meeting of the Académie des Sciences, and announced that Franklin's views of the identity of the fire of the storm-cloud with that of the electrical spark had been thus definitely established.

Before the success of M. Dalibard's experiment could be reported in America, however, Franklin had secured his own proof of the identity by the memorable experiment with the kite, so well known to the scientific world. He was anxiously waiting for the erection of the first steeple in Philadelphia for the opportunity which this would afford him for the support of a lofty iron rod, when the happy idea occurred to him to try, in the mean time, upon some suitable occasion, whether he could not contrive to hold up a lightning-conductor toward a storm-cloud by means of a kite. On the evening of July 4th, that is, fifty-two days after the experiment of M. Dalibard, his kite was raised during a thunder-storm, and, with the help of his son, he drew electric sparks from the rain-saturated string, as the two stood in the shelter of an old cow-shed in the outskirts of Philadelphia. He held the kite by a silken cord that was attached to a key at the bottom of the string, and with this arrangement he charged and discharged an ordinary Leyden-jar several times in succession. Franklin at first not unnaturally conceived that he had actually drawn the lightning down from the storm-cloud. He was, however, no doubt mistaken in this. The storm-cloud had inductively excited the neighboring surface of the earth, and what Franklin saw was the electric stream escaping out through the wet string toward the storm-cloud to relieve the tension set up by this induction. It was in the summer of the same year, after the performance of this world-renowned experiment with the kite, that Franklin attached to his house a lightning-conductor, which was composed of an iron rod, having a sharp steel point projecting seven or eight feet above the roof, and with its lower end plunged about five feet into the ground.

As a matter of course, the new doctrine of Franklin and his allies