"The proponents of the circular-universe theory were more right than they knew," Doc said, beaming and waggling his beard. "There would seem to be only three major planes of existence, each existing in a state of reciprocal contiguity to the other two. "I suspect also that spherical space is actually a unilateral continuum of three layers, restricting lateral transit to one direction in much the same fashion as a rectifying crystal governs the flow of electrons. That would explain why the Twisters could force entrance to the Blazers' dimension, once you destroyed the strain-bubble in superspace, but could not enter our plane from their own subspatial continuum." "It's all physics to me," I said, holding Dora's hand and feeling almost safe again. "Only one thing worries me--did the Blazers lose the rhubarb we ran out on or will we have them back in our hair again some day?" Doc gave me a startled squint and fuzzed his beard goatishly. "Get that model generator out of the gyro," he ordered, sounding like his old self. "We'll never know what the situation really is unless we reactivate the Di-tube and--" "And start that ratrace again?" I yelled. I could see the whole crazy business happening over and over in a sort of vicious cosmic circle, and the thought made my scalp crawl. "Over my dead body you will!" Dora and I had planned to find a minister next but the big moment had to wait. I had one final adjustment to make on that infernal Di-tube model first. I made it on the spot--with a large sledgehammer. * * * * * _Dr. Einstein has received a multitude of well-deserved honors but as far as we know science fiction has yet to do him direct homage. And surely he rates it--for had he not, some sixty years ago, come up with his full-born theory of the fourth dimension (and won worldwide publicity for said dimension) STF would have been deprived of one of its basic staples. Without the fourth (and fifth, sixth, seventh and so on) dimension, authors of speculative fantasy would have been left stumbling amid the distorted metaphysics of their Gothic forerunners--and would thereby have been constantly at war with the clergy. Thanks to Dr. Einstein they can roam the dimensions at will, threatened by no purgatory except that of creative writing itself or of the possibility of a rejection slip._