This ray is separated from the other rays of the sun by means of finely adjusted instruments placed upon the roof of the huge building, three-quarters of which is used for reservoirs in which the ninth ray is stored. This product is then treated electrically, or rather certain proportions of refined electric vibrations are incorporated with it, and the result is then pumped to the five principal air centers of the planet where, as it is released, contact with the ether of space transforms it into atmosphere.
There is always sufficient reserve of the ninth ray stored in the great building to maintain the present Martian atmosphere for a thousand years, and the only fear, as my new friend told me, was that some accident might befall the pumping apparatus.
He led me to an inner chamber where I beheld a battery of twenty radium pumps any one of which was equal to the task of furnishing all Mars with the atmosphere compound. For eight hundred years, he told me, he had watched these pumps which are used alternately a day each at a stretch, or a little over twenty-four and one-half Earth hours. He has one assistant who divides the watch with him. Half a Martian year, about three hundred and forty-four of our days, each of these men spend alone in this huge, isolated plant.
Every red Martian is taught during earliest childhood the principles of the manufacture of atmosphere, but only two at one time ever hold the secret of ingress to the great building, which, built as it is with walls a hundred and fifty feet thick, is absolutely unassailable, even the roof being guarded from assault by air craft by a glass covering five feet thick.
The only fear they entertain of attack is from the green Martians or some demented red man, as all Barsoomians realize that the very existence of every form of life of Mars is dependent upon the uninterrupted working of this plant.
One curious fact I discovered as I watched his thoughts was that the outer doors are manipulated by telepathic means. The locks are so finely