UNDERGROUND WATERS AND MINERAL VEINS. 641 



nants, or the wood, without losing its texture, has been completely 

 replaced by peroxide of iron and quartz. 



Nothing is clearer than the intervention of subterranean waters 

 in the origin of many masses of calamine, in which zinc occurs in 

 the condition of a carbonate and a hydrated silicate, at Veielle- 

 Montagne, for example, not far from Aix-la-Chapelle. The mining- 

 works have enabled us to recognize and follow the channels of 

 the generating springs in all their details. The calcareous walls 

 between which they made their way have been attacked, and, as 

 we have just seen to have been done with peroxide of iron, zinc- 

 mineral has been gradually substituted for carbonate of lime. 

 The springs that held the mineral in solution issued from faults, 

 and insinuated themselves into the permeable strata, flowing upon 

 the surface of the impermeable beds. Vestiges of fossil shells, 

 sometimes including the minerals of zinc and lead, in Westpha- 

 lia, for example, likewise attest the substitution of metallic com- 

 binations for limestone. The lead and silver mines of Laurium, 

 one of the principal sources of Athenian wealth, which figured in 

 the budget of that state from the year 520 b. c, have revealed, 

 perhaps still more evidently, in their vast excavations, the same 

 processes of Nature. 



Similar instances occur in many other countries. We cite in 

 France the various calamine beds on the circumference of the 

 central plateau ; and, in the United States, in the Rocky Mount- 

 ains, the important beds that have given rise to the towns of 

 Eureka and Leadville. Notwithstanding local differences, all 

 these masses of calamine present striking analogies, quite inde- 

 pendent of the age of the beds in which they are spread. The 

 metallic sheets are always in the same relation of situation with 

 respect to the permeability and chemical nature of the rocks as 

 they would be to-day, if the metalliferous waters were continuing 

 to flow. It is thus made possible to determine exactly all the 

 ruling conditions of these ancient zinc-bearing streams. 



Phosphorus is most usually found in the crust of the earth in 

 the state of phosphate of • lime or phosphorite. It is extracted 

 for the wants of agriculture from certain layers of the stratified 

 beds and in the cretaceous formation, particularly in the beds 

 called the gault, the same as those from which flows the water of 

 the well of Grenelle. This mineral has been worked very actively 

 since 1855 in several of the departments of France, in England, 

 Bavaria, North Germany, Russia, Spain, and Poland. It also 

 exists in remarkable quantities in the Jurassic. It often, in 

 these beds, contains animal forms, as of bones, indicating that 

 it has passed through life. But when it appears in eruptive rocks 

 and metalliferous veins, its origin is wholly independent of the 

 action of organized beings. Like the metals, the phosphorus now 



VOL. XXXIII. 41 



