CHEMICAL. 261 



(unless where steep and rocky) would form a low fringing 

 terrace, here composed of gravel and shingle, there of sand 

 and shelly debris, and in another portion of silty sedi- 

 ments. So it is with these ancient beaches ; their compo- 

 sition is quite analogous, and their organic remains differ 

 with their relative antiquities, or, which is the same thing, 

 with their elevation above the existing sea-level. Such 

 aDcient sea-margins, at various heights (9, 25, 40, 63, and 

 120 feet), are very obvious along our own coasts, and, as 

 already adverted to under " Crust-Motions" (Sketch No. 3), 

 at still greater elevations (400 or 600 feet) along the shores 

 of Scandinavia, Spitzbergen, Siberia, Greenland, and arctic 

 North America. In South America also, both on the 

 Atlantic and Pacific sides, similar terraces are frequent and 

 boldly marked those in Peru and Chili containing the 

 " salinas," so valuable as the repositories of the salts of 

 soda, potash, and other kindred substances.* Wherever 

 they occur these ancient beaches notch the earth's surface 

 like a great scale of time descending from the glacial 

 epoch down to the present day ; all that is wanting being 

 the numerical expression of their successive stages in years 

 and centuries. 



* The most important of these saline deposits (scientifically as well as 

 commercially speaking) are those of Iquique in Peru. From six to four- 

 teen leagues from the coast, and running parallel with it through the pro- 

 vince, at an elevation of 3000 feet or thereabouts, is the pampa of Tara- 

 mugal. This plain or pampa has evidently been a sea-lake, and in all 

 likelihood the result of elevation by volcanic agency. There are other 

 minor terraces or old sea-flats between the main pampa and the sea, but 

 that of Taramugal is the most important and productive. It consists in 

 some parts of many feet in thickness of sand indurated with salt, soft sand 

 with crystals of nitrate, and true caleches of concreted nitrate of soda 

 and stony debris. The other salts found in the deposit are chloride of 

 sodium (common salt), biborates of lime and soda, sulphates of lime and 

 soda, magnesian alum, &c. Iodine also exists with the nitrate, and 

 throughout the calacheros traces of boracic acid have been found in the 

 water the whole pointing unmistakably to the marine origin of the 

 deposits. 



