A]!^NIVERSAEY ADDEESS OF THE PRESIDENT . U 



of the hot water. This agent of perpetual change breaks up the 

 pelagonites, clinkstones, trachytes, traps, and lavas ; by liquid flow- 

 ing, or steam condensing, it removes the separated parts, dissolving 

 some, depositing others, and giving rise to continual new earthy com- 

 binations, diversified by sulphates and sulphurets. 



Professor Daubree, of Strasburg, one of that distinguished band 

 of Frenchmen who combine the experience of the engineer with the 

 skill of a chemist and the zeal of a geologist, has shown how the 

 natural action of the warm springs flowing from the Yosges Moun- 

 tains has generated zeolitic and other minerals, differing in their 

 nature according to the materials which they traverse. The waters 

 of Plombieres, issuing from the granitic region, and specially from 

 veins in it, which yield fluor-spar and quartz, with a temperature 

 not exceeding 73° C. (163-4 F.), hold silicates (chiefly of potash) and 

 fluorides in solution. These ^vaters, acting on the varied mass of 

 bricks, cement, and mortar, which make the cement employed in the 

 old Roman bath-channels at Plombieres, have penetrated the mass, 

 and generated in the cavities apophyllite, chabasite, and other zeo- 

 litic minerals — opal, arragonite, calc-spar, fluor-spar, hydrocarbonate 

 of magnesia, &c. Not that all the materials of these minerals have 

 been brought by the water and deposited by it, for the material 

 traversed has contributed its effect, and has undergone transforma- 

 tion. Apophyllite, a silicate of lime, is found in the mortar, and not 

 in the brick ; while chabasite, a double silicate of alumina and po- 

 tassa, is found only in the brick. 



These remarkable results suggested to the author a great and evi- 

 dent analogy to the exhibition of zeolites in rocks of the eruptive 

 igneous class. Basalts and amygdaloids often contain zeoKtic mine- 

 rals, which have been formed in cavities subsequently to the first con- 

 solidation of the rock, so that examples might be chosen from the 

 more porous varieties hardly distinguishable from the metamorphic 

 concrete of Plombieres. This identity of results demands the ad- 

 mission of a similar origin. With higher temperatures than that of 

 the Yosgian springs, and under higher pressures, it is conceivable that 

 a still larger range of mineral aggregates, even anhydrous silicates, 

 might be displaced and replaced ; and thus, for the filling of some 

 mineral veins and many metamorphic phaenomena, not heat, but 

 heated solutions, would appear to be agencies both real and suffi- 

 cient.* The same author has, however, shown us the production of 

 oxide of tin and quartz, by sublimation of fluorides, in presence of 

 aqueous vapour, and other facts bearing on the production of sul- 

 phurets and silicates by heat alone t. 



Yolatile fluorides, according to Ste. -Claire De\411e, acting on va- 

 pour of water and oxygenized compounds, occasion mutual decom- 

 position and exchange of elements. Thus, for example, volatile 

 fluoride of aluminium, acting on boracic acid, occasions the produc- 



* ' M6moire sur la Eelation des Sources Thermales de Plombieres,' &c. (Ann. 

 des Mines, 1858). 



t ' Sur la production artificielle de quelques especes minerales ' (Ann, dts 



Mines, 1850). 



