The first man who appeared to have any inkling of the real way of solving the problem of a “flying chariot,” and who in dim fashion seems to have foreshadowed the invention of the balloon, was that wonderful genius, Roger Bacon, the Learned Friar of Ilchester, the inventor or re-inventor of gunpowder, who lived in the thirteenth century. He had an idea--an idea which was far ahead of his times, and only proved to be true hundreds of years after--that the earth’s atmosphere was an actual substance or “true fluid,” and as such he supposed it to have an upper surface as the sea has, and on this upper surface he thought an airship might float, even as a boat floats on the top of the water. And to make his airship rise upwards to reach this upper sea, he said one must employ “a large hollow globe of copper or other similar metal wrought extremely thin, to have it as light as possible, and filled with _ethereal air_ or liquid fire.” It is doubtful whether Bacon had very clear ideas of what he meant by “ethereal air.” But, whether by accident or insight, he had in these words hit upon the true principle of the balloon--a principle only put into practice five centuries later. He saw that a body would rise upwards through the air if it were filled with something lighter than air, even as a body will rise upwards through the water if it is made of, or filled with, something lighter than water. We know that if we throw an empty bottle tightly corked into the sea it does not sink, but rises upwards, because it is filled with air, which is lighter than water. In the same way exactly a light bag or balloon which is filled with some gas which is lighter than air will not stay on the surface of the ground, but will rise upwards into the sky to a height which depends upon its weight and buoyancy. Later philosophers than Bacon came to the same conclusion, though they do not seem to have seen matters more clearly. As recently as 1755 a certain learned French priest actually suggested that since the air on the top of high mountains is known to be lighter than that at an ordinary level, men might ascend to these great heights and bring down the light air “in constructions of canvas or cotton.” By means of this air he then proposed to fly a great machine, which he describes, and which seems to have been as large and cumbersome as Noah’s Ark. Needless to say, the worthy Father’s proposal has never yet been put into practice.