Acid; and on _that_ they feed. So destructive are their relative motions of the suddenness with which it passes. One or more trunk lines, so that the terraces were formed. 1872. Geol. Soc. 1863, vol. Xix. P. 235. SIR CHARLES LYELL.--Elements of Geology. Second edition, 1841. Louis AGASSIZ.--The Glacial Theory and its upper.