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To Jason Gridley of Tarzana, discoverer of the Gridley Wave, belonged the credit of establishing radio communication between Pellucidar and the outer world.

It was my good fortune to be much in his laboratory while he was carrying on his experiments and to be, also, the recipient of his confidences, so that I was fully aware that while he hoped to establish communication with Pellucidar he was also reaching out toward an even more stupendous accomplishment-he was groping through space for contact with another planet; nor did he attempt to deny that the present goal of his ambition was radio communication with Mars.

Gridley had constructed a simple, automatic device for broadcasting signals intermittently and for recording whatever might be received during his absence.

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, — the 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 mastermind 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.

John Carter being absent from Helium, a fast flier had been dispatched to Duhor bearing an urgent request to Paxton to come at once to the twin cities and endeavor to determine if in truth the signals they were receiving actually originated upon the planet of his birth.

Upon his arrival at Helium, Paxton immediately recognized the Morse Code signals and no doubt was left in the minds of the Martian scientists that at last something tangible had been accomplished toward the solution of inter-communication between Jasoom and Barsoom.

Repeated attempts to transmit answering signals to Earth proved fruitless and then the best minds of Helium settled down to the task of analyzing and reproducing the Gridley Wave.

They felt that at last they had succeeded. Paxton had sent his message and they were eagerly awaiting an acknowledgment.

I have since been in almost constant communication with Mars, but out of loyalty to Jason Gridley, to whom all the credit and honor are due, I have made no official announcement, nor shall I give out any important information, leaving all that for his return to the outer world; but I believe that I am betraying no confidence if I narrate to you the interesting story of Hadron of Hastor, which Paxton told me one evening not long since.

I hope that you will enjoy it as much as I did.

But before I go on with the story a brief description of the principal races of Mars, their political and military organization and some of their customs may prove of interest to many of my readers. The dominant race in whose hands rest the progress and civilization-yes, the very life of Mars-differ but little in physical appearance from ourselves. The fact that their skins are a light reddish copper color and that they are oviparous constitute the two most marked divergences from Anglo-Saxon standards. No, there is another-their longevity. A thousand years is the natural span of life of a Martian, although, because of their war-like activities and the prevalence of assassination among them, few live their allotted span.

Their general political organization has changed little in countless ages, the unit still being the tribe, at the head of which is a chief or jed, corresponding in modern times to our king. The princes are known as lesser jeds, while the chief of chiefs, or the head of consolidated tribes, is the jeddak, or emperor, whose consort is a jeddara.

The majority of red Martians live in walled cities, though there are many who reside in isolated, though well walled and defended, farm homes along those rich irrigated ribbons of land that we of earth know as the Canals of Mars.

In the far south, that is in the south polar region, dwells a race of very handsome and highly intelligent black men. There, also, is the remnant of a white race; while the north polar regions are dominated by a race of yellow men.

In between the two poles and scattered over all the and waste lands of the dead sea bottoms, often inhabiting the ruined cities of another age, are the feared green hordes of Mars.

The terrible green warriors of Barsoom are the hereditary enemies of all the other races of this martial planet. They are of heroic size and in addition to being equipped with two legs and two arms apiece, they have an intermediary pair of limbs, which may be used at will either as arms or legs. Their eyes are set at the extreme sides of their heads, a trifle above the center, and protrude in such a manner that they may be directed either forward or back and also independently of each other, thus permitting these remarkable creatures to look in any direction, or in two directions at once without the necessity of turning their heads.