322 



THE FOP.MATION OF SOILS. 



nean ngency; for so recently as 1805, the bed of part of the sea 

 and of the Indus, was y)ermanemly changed by an earthquake, near 

 Ciilch, on the coast of Bombay. 



The increase of land at the mouth of the Nile, and of many Eu- 

 ropean rivers, is well known. Adria, which was once a port of the 

 Adriatic Sea (to which it gave its name), is now six leagues inland. 

 In lakes, the diminution of the surface, by the gradual increase of 

 land at the mouths of rivers which flow into them, is still more re- 

 markable. The mud and debris brought into the lake of Geneva by 

 the Rhone, and deposited near its entrance, have made the land ad- 

 vance two miles in the space of 1700 years, — the Roman harbour 

 Portus Valesiag being now that distance from the lake. All the lakes 

 in Savoy and Switzerland, and in our own island, are gradually di- 

 minishing, by similar causes. To multiply instances of this kind 

 would be incompatible with the limits of the present volume ; every 

 attentive observer must have noticed them in the course of his travels. 



All the most fertile parts of the globe were formed by alluvial de- 

 positions : alluvial agency appears to have been the means employed, 

 in the economy of nature, to prepare the world for the residence of 

 social and civilized man. The most ancient cities of which we 

 have any authentic record, Babylon, Nineveh, and Thebes, were 

 founded in the midst of alluvial soils, deposited by the Euphrates, 

 the Tigris, and the Nile : indeed, it does not appear unreasonable to 

 believe, that the formation of soils for the support of vegetables and 

 animals, is the final end to which all terrestrial changes ultimately 

 refer. 



It has been justly observed by Dr. Paley and others, that in the 

 peculiar conformation of the teeth in graminivorous animals, and in 

 the production of grasses which serve them for food, we may trace 

 evident marks of relation, and of a designing intelligent cause. 

 With equal reason must we admit, that the destruction of mountains, 

 and the formation of soils for the support of the vegetable tribes, are 

 provided for by the same cause, and are part of a regular series of 

 operations in tiie economy of nature. Hence also we may infer, 

 that those grand revolutions of the globe, by which new mountains op 

 continents are elevated from the deep, are parts of the same series, 

 extending through ages of indefinite duration, and connecting all the 

 successive phenomena of the material universe. 



By a wise provision of the Author of nature, it is ordained, thai 

 those rocks which decompose rapidly, are those which form the most 

 fertile soils; for the quality of soils, depends on the nature of the 

 rocks from which they were formed. Granitic and siliceous rocks 

 form barren and sandy soils ; argillaceous rocks form stiff clay 5 and 

 calcareous rocks, when mixed with clays, form marl ; but when not 

 covered by other strata, they support a short, but nutritious veg- 

 etation. For the formation of productive soils, an intermixture of 

 the three earths^—clay, sand, and lime — is absolutely necessary. 



