The air being lighter at the summit of a mountain than at the level of the sea, by filling this vessel with the mountain air, it must displace, being on the ground, a mass of air of greater weight than that with which it was filledplus the weight of the craft and its cargo. This vessel would have to float in the atmospheric level of the "hail belt", as the atmosphere there is a thousand times lighter than water, while in the strata above this, into which the top of the cube would extend, the air is two thousand times lighter than water.