But what force was it that pressed earth's life thus upward through the paths of change? What force was it that caused all this vast, slow evolution of earth's creatures into different creatures, that had begun with the first jelly-like life-forms on earth and had forced the tide of life up from them to the forms of today, that still was slowly changing them? That question none could answer. Environment did not explain it, for though environment had certain effects on the life-forms in it, it was not responsible for that deep, vast tide of upward evolution. Mendelism had seemed for a time to suggest an explanation but had failed in the end to do so. Some great force there was, all knew, that pressed life always up the path of evolution, but none had ever guessed what that force might be, and the thing had come to be accepted at last as one of the insoluble problems of science. And now Grant claimed that he had solved it! "For long," Grant's statement said, "I have held that since evolutionary change is unquestionably caused by some definite and omnipresent force acting upon all life on earth, it should be possible to discover the nature of that force. I will not recount the work of months which I have spent in constant search for this force, but will say that finally I have been successful, have identified the force which my experiments show beyond all doubt to be the single force responsible for the upward course of evolution on earth. That force is a vibratory force, a vibration unknown to earth's physicists prior to my discovery of it, which has as its source the sun! "The sun, we know, is a vast mass of incandescent matter which ceaselessly pours out part of its matter transformed into energy. The energy thus formed, flooding out in all directions from the sun through space, takes various forms. At a certain vibratory frequency, it takes the form of light and illuminates our day. At another frequency, it is radiant heat, warming our world. At still another, it is the cosmic ray so recently discovered. There are many others, known to us, and still more of which we know nothing as yet, a vast welter of vibratory forces flooding endlessly outward from the sun. And it is one of those vibrations, one which we well may call the evolution vibration, which is responsible for the evolutionary change of all life on earth.