In proceeding now to a study of levity we shall not start, as might be expected, with plants or other living forms. We are not yet equipped to understand the part played by levity in bringing about the processes of life; we shall come to this later. For our present purpose we shall look at certain macrotelluric events - events in which large areas of the earth are engaged - taking our examples from meteorology on the one hand and from seismic (volcanic) processes on the other.