"Yet if all are changing—we two also must be changing!" I exclaimed, and he nodded.

"We two are already a little affected as all men are, more or less. Our lapses of memory, the difficulties we have in our work now, these things in the last days are the result of this world atavism in us, just as the crimes and accidents filling earth are. And we two must protect ourselves against this tremendous change, whatever we do, for on us depends the one chance of halting Grant's terrible work. The world will never believe that that dread work is really going on until it is too late, so you and I must not change!"

Ferson went swiftly on to explain his idea. This was none other than to construct two small projectors that would each automatically and ceaselessly generate artificial evolution vibrations, vibrations affecting a limited range as the sun's vibrations had affected all earth. These projectors in their compact cases could be worn on our bodies by each of us without being noticeable, and would keep each of us always thus in the range of the vital vibrations, so that we would not be affected by the world-wide absence of that which was causing this world atavism. Whatever great dampening wave Grant was sending out toward the sun to neutralize its evolution vibrations would not, of course, affect the vibrations of our own little projectors.

The next two days saw us at work upon these projectors. The method of producing the evolution vibrations we knew, for as I have mentioned, they had been artificially produced in a small way by physicists upon Grant's first announcement of his theory. The second day, therefore, saw our projectors complete, small flat black cases that were strapped to our belts without being noticeable, each holding the tiny but marvelously powerful batteries that were the current-source, and the compact little generator that automatically and unendingly released the vital evolution vibrations for a range of several feet. With these completed and working, and secured thus by them from being ourselves affected by the terrible atavism that was upon the races of man, we began our greater work of locating Grant and the apparatus by which he was shutting off the sun's vibrations and loosing this horror on the earth.

For horror it had now become, and the world was waking up to its true nature as every sort of brutal passion was released in terrible crime over it, and as the inexplicable mindlessness of men brought on terrific accidents. Already a dozen of the greatest governments in coöperation had called a conference of earth's greatest scientists at New York to explain or to halt at least the horror that was sweeping earth. To that conference they came with each a different and more incredible explanation of the thing, and to it went Ferson and I to give them the true explanation and to turn them toward the search for Grant that might yet save humanity. But that explanation was never given, for Ferson's first mention of world atavism was greeted with incredulous cries, and when he went on to mention Grant, such a derisive storm arose, that he was forced bodily from the meeting, leaving the scientists disputing fiercely over the most impossible of theories, supporting and opposing those theories by blows.

For they, like the rest of humanity, seemed incapable now of clear and sustained thought upon any subject. Even Ferson and I, working day and night in the isolated upper Manhattan laboratories of the university, were able to see clearly what was happening about us. We were living, eating, sleeping at the laboratories by this time, for all means of transportation and all industrial activities were ceasing. Great masses of men roamed the streets of the city, some forming into gangs that made life terrible for the others, the rest engaged in indiscriminate looting. The great London riot and the abortive outbreak in lower New York had now taken place, and it was evident to all that the last shadow of law and order in the city was vanishing, for more and more the troops and police who maintained it were engaging in the rioting themselves.

News came still a little, in incoherently written and erratically printed sheets, for a few days, and it was thus we learned of the huge Chicago riot and subsequent fire. It marked the beginning of the end. Within a few days more utter lawlessness reigned over New York, corpses lay in its streets and looters were everywhere. The university buildings, deserted now by all but ourselves, were not attacked except on a few occasions by the looting swarms, there being no food or other desirable things in them, and Ferson and I had rifles and pistols in our laboratory to repel the ragged and brutal gangs that might attack us.

In those terrible days we were occupied heart and soul in the work of locating Grant and whatever mechanism it was by which he was casting this doom on humanity. It was Ferson's idea that the great damping wave, which Grant must be sending toward the sun to halt the play of its endless evolution vibrations, would affect certain recording instruments, if the correct frequency for their circuits could be found. Once that was found, by observing the amount by which the instruments were affected at different locations by the waves of the great damping vibration, we could calculate and chart that great wave's source with some degree of accuracy. It seemed to me a very slender chance, yet I knew as well as did Ferson that it was the one possible way. Grant, we knew, would have protected himself, as we had, by a small artificial projector of the vibrations.

So in those fearful days we worked with the recording instruments, watching them at each new trial for some indication of the force whose source we sought. The whole great mass of New York's giant structures that stretched southward and downward from our laboratory lay now in complete darkness each night; the last wonted activities of civilization having ceased in it as elsewhere. Ragged hordes of savages roamed it, savages so hairy and crouching and brutal of face, seeming each day more prognathous of jaw and slanting of brow and animal-like of eye, that we knew them to be troglodytes, cave-men, men such as humanity had been ages before and such as it was over all earth now.

We saw them occasionally prowling through the university grounds in search of food, shambling toward us with lowering brows to attack us when they glimpsed us, but fleeing in fear when we fired over their heads. For none of them could manipulate so complicated a thing as a firearm. All earth's hundreds of millions were prowling their way in just such brutal bands, thrown back to the state that had been man's before history's dawn. And ever more brutal and hairy and animal-like they were becoming as they slipped back farther still, back from troglodyte to ape! Mankind was gone, transformed into these still-changing brutes—all except Ferson and me.