“Nearly all the moon’s volcanoes are on the hither portion, the volcanic region occupying about two-thirds of the whole surface of the moon. The weight of bodies on the hither side is appreciably less than on the further side. These facts are supposed to be due to the earth’s attraction neutralizing that of the moon and having resulted in building up the vast protuberance or table land (of light and porous material) on this side, the latter is often called, by us the “Mundane Hump” in recognition of the earth’s instrumentality in its formation. The interior continent is often spoken of as the “Pocket” by the people on the further side; or sometimes as the “Chest”, and the “Hump” is called its Lid. “The further side of the moon is called the Exterior Continent, but often humorously designated by the people of the “Pocket”, as the Out-door Continent.” “But,” said I, “what a strange life it must be in those underground cavities. I suppose of course you can have nothing better than artificial light there?” “True,” he said, “our light is mostly artificial, but it is made as bright as we can bear it. It is electric light, but it is regulated to be quite equal to sun light and it never goes out. There is no night in the underground country, as there is outside.” “This is wonderful!—But where do you get the power to furnish this light? Have you got waterfalls and coal beds down there?” “We have many waterfalls, but do not utilize them to any great extent for their power and we have a considerable amount of coal, which however we do not use for fuel, but reserve for food purposes, to be drawn upon as may be required.” “Is stone coal what you have to eat then?” I here broke in. With exasperating deliberation, he gave me an admonitory poke with his right joker. “One thing at a time—one thing at a time. You wanted to know where we get power to turn into electric lighting. It is the power of gravity. If one of your perpetual motion cranks understood the secret of the use of the repulsion of gravitation, he could contrive a perpetual motion in an hour and a half. We have many forms of such machines that have been in use for ages. One of these is the pendulum machine. This consists of a pendulum weighing from a few pounds to many tons and so contrived that when it reaches the lowest part of its swing it automatically turns on the repulsion of gravitation, which reinforces its momentum on the ascending part of its arc, enough to compensate for the work done by it and the friction of the machine. Another machine is the oscillating balance. This consists of weights at each end of a beam balanced in the middle and so governed by an automatic shunting apparatus, that one of the weights is under the influence of attraction while the other is under that of repulsion. When the former has reached the bottom of its oscillation and the latter the top, the force is reversed in each and so the motion is perpetual.