AMEEICAN GEOLOGY DECADE OF 1850-1859. 459 



of, or indifference toward, much of the work that had been done in the 

 West and Northwest, and his ideas regarding the early history of the 

 globe were not the most advanced. Heat was regarded as at first 

 the predominant and active element. As the activity of fire dimin- 

 ished, that of the antagonistic element, water, increased. The first 

 was paroxysmal in its action, the latter constant. In America he 

 found the evidences of aqueous agencies on a grand scale, but "vol- 

 canic lire'' 1 seemed so far a thing of the past that it was " impossible 

 to obtain specimens even for laboratory illustration." 



Fire or heat, he wrote, acts in four ways: (1) In the elevation of 

 areas by expansive forces beneath the crust; (2) by the transference 

 of fused matter from the interior to the surface; (3) by producing 

 areas of subsidence, caused by this loss of matter from beneath; and 

 (4) the elevation or depression of areas simply through expansion and 

 contraction of strata by heat and cold. The internal heat he regarded 

 as effective in sustaining "that degree of temperature which is best 

 fitted to the organic and structural conditions of living beings" on the 

 earth. 



The classification adopted was essentially the same as that put out 

 in his North Carolina report (p. 431) and need not be repeated here. 



The pyrocrystalline rocks, it may be stated, however, he regarded 

 as the results of the primary consolidation of the earth's crust. The 

 fact that some of these occurred in dikes he thought to be due to the 

 Assuring of the earlier-cooled portions of the crust by shrinkage and 

 the forcing up through these fissures of the lower, still unconsolidated 

 portion. He imagined that the age of rocks might be deduced from 

 their crystalline state, the older having been subjected to greater heat 

 and hence becoming most perfectl} T fused and most highly crystalline 

 on cooling. The granites were, therefore, regarded as the first prod- 

 ucts of cooling and the oldest of rocks. 



Emmons regarded concretions and nodules as S3 7 mmetrical bodies 

 due to "a force by virtue of which the molecules are really transferred 

 to central points where, by constant accumulation,' 1 the}^ form the 

 concretion. The parallel planes of the rhombic forms in limestones 

 and slaty rocks, and jointed structure in general, "admits of the same 

 explanation." The concentric weathering shown b} T massive rocks 

 was referred to the same cause. Further than this, he regarded the 

 phenomena of rift and grain in a massive rock as identical with cleav- 

 age in a simple mineral. Such rocks "are not only composed of 

 crystallized minerals, but they are crystalline in the mass." 



The serpentine of Syracuse, New York, he considered a magnesian 

 i/ock altered b} r proximity to eruptives, and he still adhered to the idea 

 of the igneous origin of the crystalline limestones of St. Lawrence 

 County, as announced in his New York report. For the first time in 

 an American text-book there was here recognized the relationship 



