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Destroying Effects of Water. 27 the year, and as every rain carries along with it a quantity of the foil, very obvious changes muft in this manner be induced on the furface of the globe. Thunder-ftorms and water-fpouts, al though more uncommon phenomena, produce more confulerable changes, and this either alone, or when their waters join or flow into rivers. Thefe deprive whole diftridts of their foil to the bare rock ; they fometimes even form 1 fmall ravines, and break down and carry away great maiTes of rock, that were either formerly much rent, or of fuch a form, as to be eafily overpowered by water. If fuch changes take place in the low land, they muft be vaftly more .confiderable in the high land. The thaw-floods that take place in low coun tries towards the end of winter and beginning of ■fpring, and in mountainous diftridfcs during fum- mer, occafion ftill greater changes on the furface of the earth. Their efiedts are truly frightful, particularly when accompanied with rain. The declivities in low countries, over which water flows, are lefls confiderable than in high countries ; and befides, the \vater can extend itfelf farther in low and flat countries; hence its deftroying effedts are diminifhed in intenfity. In mountainous coun tries, on the contrary, the fall is much greater than in flat countries, and the water is comprefl'ed into narrow rocky valleys; hence it follows, that jain-floods muft be more deftrudtive, the more confiderable