For a period of five minutes the Gridley Wave carried a simple code signal consisting of two letters, "J.G.," out into the ether, following which there was a pause of ten minutes. Hour after hour, day after day, week after week, these silent, invisible messengers sped out to the uttermost reaches of infinite space, and after Jason Gridley left Tarzana to embark upon his expedition to Pellucidar, I found myself drawn to his laboratory by the lure of the tantalizing possibilities of his dream, as well as by the promise I had made him that I would look in occasionally to see that the device was functioning properly and to examine the recording instruments for any indication that the signals had been received and answered. My considerable association with Gridley had given me a fair working knowledge of his devices and sufficient knowledge of the Morse Code to enable me to receive with moderate accuracy and speed. Months passed; dust accumulated thickly upon everything except the working parts of Gridley's device, and the white ribbon of ticker tape that was to receive an answering signal retained its virgin purity; then I went away for a short trip into Arizona. I was absent for about ten days and upon my return one of the first things with which I concerned myself was an inspection of Gridley's laboratory and the instruments he had left in my care. As I entered the familiar room and switched on the lights it was with the expectation of meeting with the same blank unresponsiveness to which I was by now quite accustomed. As a matter of fact, hope of success had never been raised to any considerable degree in my breast, nor had Gridley been over sanguine--his was merely an experiment. He considered it well worth while to make it, and I considered it equally worth while to lend him what small assistance I might. It was, therefore, with feelings of astonishment that assumed the magnitude of a distinct shock that I saw upon the ticker tape the familiar tracings which stand for the dots and dashes of code. Of course I realized that some other researcher might have duplicated Jason's discovery of the Gridley Wave and that the message might have originated upon earth, or, again, it might be a message from Jason himself in Pellucidar, but when I had deciphered it, all doubts were quickly put to rest. It was from Ulysses Paxton, one time captain, --th U.S. Infantry, who, miraculously transported from a battlefield in France to the bosom of the great Red Planet, had become the right hand man of Ras Thavas, the master mind of Mars, and later the husband of Valla Dia, daughter of Kor San, Jeddak of Duhor. In brief, the message explained that for months mysterious signals had been received at Helium, and while they were unable to interpret them, they felt that they came from Jasoom, the name by which the planet Earth is known upon Mars.