ABSTRACT
Denudation means the removal of disintegrated crystalline rocks to a lower level. Until the last twenty or thirty years, most geologists thought that the waves of the sea were the chief agents in work of denudation; but we may now feel sure that air and rain, aided by streams and rivers, are much more powerful agents that is if we consider the whole area of the land. In all humid, even moderately humid, countries, worms aid in the work of denudation in several ways. The several humus-acids, which appear, to be generated in the bodies of worms during the digestive process, and their acid salts, play a highly important part, according to the recent observations of Mr Julien, in the disintegration of various kinds of rocks. It has long been known that the carbonic acid, and no doubt nitric and nitrous acids, which are present in rain water, act in like manner.
