A lake evaporates upward and thus gradually dries up; but when two lakes are joined they do not dry up so readily, for one replenishes the other. It is the same in the field of knowledge. Knowledge should be a refreshing and vitalizing force. It becomes so only through stimulating intercourse with congenial friends with whom one holds discussion and practices application of the truths of life. In this way learning becomes many-sided and takes on a cheerful lightness, whereas there is always something ponderous and one-sided about the learning of the self-taught.