The changes which Daubree has shown to have been produced by the alkaline waters
of Plombieres in the Vosges, are more especially instructive. (Daubree Sur le
Metamorphisme Paris 1860.) These waters have a heat of 160 degrees F., or an
excess of 109 degrees above the average temperature of ordinary springs in that
district. They were conveyed by the Romans to baths through long conduits or
aqueducts. The foundations of some of their works consisted of a bed of concrete
made of lime, fragments of brick, and sandstone. Through this and other masonry
the hot waters have been percolating for centuries, and have given rise to
various zeolites-- apophyllite and chabazite among others; also to calcareous
spar, arragonite, and fluor spar, together with siliceous minerals, such as
opal-- all found in the inter-spaces of the bricks and mortar, or constituting
part of their re-arranged materials. The quantity of heat brought into action in
this instance in the course of 2000 years has, no doubt, been enormous, but the
intensity of it developed at any one moment has been always inconsiderable.
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