Up to this time, although the identity of lightning with electricity had long been suspected, it had not been at all established, and to Franklin may be said to belong the honor of doing so, although in this, as in the case of the invention of the Leyden jar, there appears to have been successful contemporaneous research elsewhere. Before performing his great experiment Franklin published a book strongly supporting the belief in the identity of the two. Once having conceived the idea of drawing electricity from the upper atmosphere, he unfortunately lost some time through waiting for the completion of the spire of a certain church in Philadelphia, from the top of which he hoped to be able to collect electricity by means of a wire, but finally hit upon the device which now fills much the same place in connection with his memory that the classical cherry tree does with Washington's--the lightning-collecting kite. This apparatus was very simply constructed, and had a pointed wire projecting a short distance above the framework. It was controlled, and electrical connection made, by an ordinary string which terminated in a short length of silk ribbon to protect the person from possible injury, and to give electricity a chance to accumulate in the system, by insulating the "line." At the end of the string proper Franklin fastened a metallic key. In company with his son he flew the kite during a thunderstorm which occurred in June, 1752; for some time no electric disturbance approached the neighborhood, and he was on the point of abandoning the experiment when he observed what he had been waiting for--the outer fibers of the string standing out from the latter by repulsive force--and, applying his knuckle to the key, he drew a spark. Subsequently, when the rain soaked the string and caused it to conduct much better, there was a fine supply of electricity, and Franklin charged a Leyden jar from the key, thus achieving the actual storage of "lightning." He continued his investigations in atmospheric electricity, and discovered that the electrification of the clouds (or of the upper atmosphere) was sometimes positive and sometimes negative. The invention of the lightning rod is due to him. Franklin sided with Watson in his belief in the single nature of the electric fluid.