Now the whole question of aerial navigation hinges absolutely and completely on that of gravitation. The great desideratum is a weightless (_i.e._, weightless in effect) aeroplane (with, of course, a virtually weightless crew, virtually weightless passengers, and a virtually weightless cargo) which can move fast or slowly as required, which can come to a stop in the air and which cannot fall. Science and industry are now within measurable distance of such virtually weightless aircraft, thanks to the investigators who have not been deterred by obloquy and ostracism from speaking with the dead. It is usually assumed in scientific circles that gravity is an unsolved mystery and is entirely beyond the scope of human control in the present state of knowledge. The assumption is well founded if by “knowledge” is meant merely that which is possessed by living human beings and derived solely from normal sources. But if there be, in reality, certain intelligences other than ordinary men and women, they may possibly be better informed with regard to the facts of the universe; and if intelligent communication be feasible as between the better informed personalities and their cousins in this life, it is conceivable that some of the latter may thus acquire information which would otherwise be unattainable. This has actually happened with regard to gravitation. Sir William Crookes more than forty years ago entered into communication with supernormal intelligences and carried out certain laboratory experiments that showed the control and modification of gravity to lie within the compass of human ability when guided by the intelligences in question. And many more experiences of a similar or of an analogous kind are on record. The facts are well established and cannot be successfully denied or explained away.