270 Springs and Artificial Fountains. 



26. The superior oolite and chalky calcareous depositions and 

 formations ; argillaceous and sandy depositions, coarse limestone, the 

 marles, the fresh water limestone or, (belonging to the) terrain lacustre 

 are more favorable than the preceding to the infiltration of waters, 

 which descend from greater elevations. These formations present 

 abundant waters in the superpositions ; they have a constant analogy 

 in their composition and properties. The predominant salts are the 

 carbonate and sulphate of lime, the sulphate and carbonate of iron, 

 and sometimes the sulphate of magnesia ; when they are filtered 

 though chalky or sandy masses, these waters are generally fresh and 

 of a good quality. 



27. They are ferruginous when they pass and infilter through, 

 pyritous earths, or mines of iron, or through pyritous argillaceous 

 earths, such as those of Passy, near Paris, and of Forges, in the 

 Seine. Inferieure, or those of Ferrienes, near Montargis, and of 

 Segrais, near Pishiviers, which issue from superior formations to coarse 

 marine limestone. 



28. The only example of sulphureous water, well attested, at this 

 time, in earths of this formation, is that which the waters of Enghien 

 present, containing sulphuretted hydrogen gas, the sulphate and mu- 

 riate of magnesia, the sulphate and muriate of lime, he. &;c. 



29. Generally, the waters, of all these earths, are of the mean 

 temperature of the place where they gush out, and are that which is 

 called cold, in opposition, to the thermal waters. 



30. Alluvial earths, like the preceding, yield abundant fresh water. 



31. Generally, their waters proceed from the filtration of rain 

 and melting snow, which penetrate, extend and flow between the 

 beds of marl, clay, or sand, where we attempt to reach them by our 

 wells. 



32. The alluvial earths, of alluvial sand and gravel, sometimes 

 present natural fountains, which indubitably proceed from more ele- 

 vated districts, and probably from secondary or primary earths ; such 

 are the fountains of Moses, near Suez, described by Monge, situated 

 on the summit of small sandy hills, raised by the winds and aggrega- 

 ted by the sulphate of lime, which the waters of these fountains hold 

 in dissolution ; such is that fountain of fresh water, flowing above the 

 waves of the Mediterranean, near Spezzia, and described by Spal- 

 lanzani ; such is the beautiful spring, in the sand bank, on the shore 

 of Alvarado, in the gulf of Mexico : this sand bank, forty years since, 

 was not more than 0.66 centimetres high, and about half a mile in 



