26 SURFACE OF THE EARTH. v CIIAP. II. EFFECTS OF WATER ON THE SURFACE OF THE earth. 2 9- T,T Aving now defcribed all the varieties of X X inequality obferved on the furface of the dry land, it will be interefting to endeavour to difcovef how thefe have been formed. Many of the elevations and hollows appear to be original formations, while others feem to be more particularly the effedts of the aftion of the atmofphere and the ocean, and volcanic fire. We fhall confider each of thefe in particular. 30. Water adts eitHer Chemically or Mechani cally on the furface of the earth : and it may fur ther be confidered, according to its Deftroying and Forming effedts. We fliall fir It confider the Mechanical Dejlroy- i n g Effects of water. Every long-continued rain convinces us of the powerful mechanical effedts of water on the fur face of the earth. The precipitated water pene trates the furface, then flows along mixed with the matter of the foil, and in its courfe forms fmall water-courfes, and occafions confiderable changes m the flat country and the declivities of moun tains. A9 it rains a very confiderable portion of the