6i6 THE POPULAR SCIENCE MONTHLY. 



though relatively in extremely feeble proportions, water is incoi-po- 

 rated in the deep masses of the terrestrial crust, in immense absolute 

 quantities, which are perhaps commensurable Avith the volume contained 

 in the seas on the surface. 



Various physical circumstances, such as the configuration of the 

 soil and the vicinity of rivers or of the sea, have always had a great 

 influence on the grouping and destinies of populations. The presence 

 of particular minerals has had a similar determining influence. The 

 useful metals, coal, and petroleum, have caused important cities to be 

 created and to grow — as Virginia City, Leadville, Eureka, Oil City, 

 and Petrolia, in the United States. 



Underground water, a more commonplace substance, which has 

 attracted much less attention, eminently deserves to be considered 

 when we seek for the natural causes that have contributed to the for- 

 mation of large agglomerations of men. Pliny the Elder remarked that 

 mineral waters had j^eopled the earth with new cities and Olympus 

 with new gods. Recent excavations in Gallic villages have brought 

 to light vast inscincB^ marble monuments, theatres, statues, mosaics, 

 and other unmistakable vestiges of a vanished luxury, as at Nereis, 

 Vichy, Plombi6res, Bagneres-de-Luchon, and Aix in Provence. Uni- 

 versal celebrity attaches to Baiae, where every Roman was ambitious 

 to have a country-house, and the ancient splendor of which is attested 

 by ruined temples and palaces. The word " bath " and its equivalents 

 in different languages form the roots of many place-names. Those 

 who lived by the manufacture of salt have necessarily grouped them- 

 selves around the marine springs from which their towns have received 

 names embodying the root-form of the word salt or its equivalents 

 — Salins, Chateau-Salins, Salival, Marsal, Salies, Salat, Saleons, Saltz, 

 Saltzbronn, Salzhausen, Salzungen, Salzburg, Hall, Reichenhall, etc. 



So populations tend to group themselves around copious fountains of 

 fresh, potable water, where the frequency of the villages is often in 

 striking contrast with the sparsity of the settlements in more arid lo- 

 calities. These contrasts result from the constitution of the soil. The 

 junction of the Jurassic formation with the impermeable clays of the 

 lias on which it rests is marked by a line of frequent springs, around 

 which habitations and villages stand thickly, as in the vicinity of 

 Metz ; while the absence of masses of population on the neighboring 

 limestones, where water is reached only «,t a great depth, is matter of 

 special remark. This abundant and regular water-supply is found un- 

 der these conditions, and at the same geological level, in many parts of 

 France, England, and Germany, where it always attracts thick popu- 

 lations. 



"While the cretaceous table-lands of Champagne lack springs, they 

 flow out in abundance at the foot of the cliffs. Many of them bear 

 the generic name of " Somme," because they are the origin or the top 

 of a brook — as Somme-Suippe, Somme- Vesle, Somme-Tourbe, Sommer 



