128 TJiA^^SACTIO^'s of the A 3i erica a Institute. 



are so many small thermometers showing tlie temperatm'e at v/liich 

 the granite was crystallized. Pressure, which increases the melting 

 point of rock when exposed to fires, greatly favors the dissolving 

 power of heated water, so that we may snp])03e that the lowest strata 

 of sediment aiid often adjacent portions of the primal nnclens being 

 permeated with water, nnder great heat and pressm'e, became softened 

 and yielding. From this softened zone come all eruptive rocks, and 

 in it are to be found the calises of volcanoes whose Various products 

 are generated by the action of heat upon the varied elements of 

 deeply buried sedementary strata. The theory which ascribes 

 volcanic products to the supposed uncooled liquid center, fails entirely 

 to account for the great diversity in composition of tlicse products, 

 all of which, wherever found, are represented in rocks of aqueous 

 origin. The distribution of inodern volcanoes shows them to be inti- 

 mately connected with comparatively recent accumulations of sedi- 

 mentary rocks; entire absence of volcanic phenomena over the 

 eastern part of this continent is thus explained. The learned lecturer 

 observed, in conclusion : "We have endeavored to show some of the 

 results of the chemical and physical laws which presided over the 

 first formation of tlie globe. We have thus seen in what manner 

 chemical and physical laws operated in giving form and order to 

 chaos, and in producing from the first nelmlous mass the various rocks 

 and minerals, the water and the air of the present habitable globe. 

 A further study of these same laws would explain the whole theory 

 of mineral springs, the formation of metallic veins, and the processes 

 connected with the growth and development of life upon our planet. 



