638 THE POPULAR SCIENCE MONTHLY. 



escape, to flow on to the fish-ponds, through a vertical chimney of 

 cut stone. Carefully examining the bricks which had been im- 

 mersed for centuries in the mineral water, I discovered that they 

 had undergone a transformation of the most interesting character. 

 New combinations, silicates of the family of the zeolites, had been 

 developed in the cavities with which the bricks were riddled; 

 chabesite in striated crystals, grouped exactly like those in Nature, 

 and with the same angles ; and christianite, the crystals of which, 

 intersecting one another in the form of a cross, are identical with 

 those of the volcanic rocks. There was, besides, a product of opal, 

 translucent and colored like drops of dew. The tissue of the 

 bricks contained little fibrous and radiated globules, which optical 

 characteristics showed to be chalcedony. The same species had 

 been formed even in the minutest pores of the brick. These min- 

 erals, of contemporaneous production, were found later in the 

 Roman masonry-works of Luxeuil and Bourbonne-les-Bains. 

 With the aid of time, thermal water had there acted chemically 

 on the bricks and on the limestone, and had engendered gradually 

 and by a curious collaboration the substances we have named, 

 without calling in the high temperature that we were ready to 

 suppose was necessary, nor water very strongly mineralized. A 

 very slow but incessant action was sufficient. Does not this dem- 

 onstration, even to the minutest particulars, account for the for- 

 mation in ancient epochs of zeolite, agate, and the substances that 

 usually accompany them ? In view of their complete similarity 

 with those of which Plombieres has revealed the history, can we 

 not say that all these minerals were reproduced in rocks still in- 

 completely cooled, by the chemical action of hot or lukewarm 

 waters which infiltrated themselves into their easily permeable 

 texture, and of which the parasitic zeolites accurately trace the 

 ancient history ? 



On account of the multiplicity and extent of the works of ex- 

 ploitation that traverse the metalliferous beds in numerous coun- 

 tries, and the mathematical exactness with which all the details 

 of their forms and composition are revealed every day, these beds 

 bring to bear very precious data on the functions as mineralizers 

 of the ancient springs. The veins of the most usual type have the 

 form of plaques rarely exceeding a few metres in thickness. 

 Horizontally, they are prolonged to considerable superficies, some- 

 times to ten or fifteen kilometres. This measurement is given by 

 the extent to which workings have been promoted, and can be 

 visibly exemplified on the surface of the ground, when the quartz- 

 ose parts of the veins, persistent against denuding agencies, ap- 

 pear as steep ridges, of imposing height, which the eye can fol- 

 low in the distance. Sometimes they stretch out like a gigantic 

 wall irregularly notched, sometimes they rise in needles. In 



