AMERICAN GEOLOGY— DECADE OF L830-1839. 309 



This view is interesting when compared with those put forward nearly 

 half a century later by one who, working under the misguided T. 

 Sterry Hunt, argued in favor of the sedimentary origin of the entire 

 series. 



Hitchcock thought it probable that the mica slate and gneisses of 

 the Hoosac Range passed laterally into one another, 'owing to a 

 decrease in the amount of feldspar in the gneissic rock. Such a 

 transition seemed to him as possible, whether the rocks were to be 

 regarded as direct crystallizations from aqueous solution or sedi- 

 mentaries crystallized through the influence of heat. He himself 

 was inclined to the belief that these schists and gneisses were meta- 

 morphosed sediments, since he could conceive of no chemical process 

 by which such a variety of minerals as those contained by them could 

 have crystallized out simultaneously from solution. Such a crystalli- 

 zation, he argued, would be differential. 



He utilized this same argument in writing on the origin of the 

 granites. These latter he looked upon as resulting from the melting 

 down of other rocks, gneisses being duo to the more or less complete 

 fusion and crystallization of feldspathic sandstone. The deeper lying 

 portions, which were most highly heated, gave rise to granitic gneiss, 

 and those further removed gave rise to the porphyritic, lamellar, and 

 schistic varieties. It will be of interest to compare these views with 

 those advanced by Clarence King nearly forty years later. 



Hitchcock classed under the name of graywacke the siliceous con- 

 glomerate of Dorchester and Roxbury (now considered as of Cambrian 

 age), and, indeed, every conglomerate sandstone and fragmentary for- 

 mation that was older than the red sandstone and coal formation, thus 

 avowedly following Humboldt." 



Under a misapprehension regarding the character of the amygdules, 

 he included under the name of varioloid wacke the melaphyr of 

 Brighton and elsewmere, as well as other altered Paleozoic lavas found 

 at Hinghani, Needham, and Saugus; also the siliceous or flinty slates 

 of Nahant and jasper of Newport. 



The red sandstones of the Connecticut Valley were rightly set down 

 as belonging to the New Red, he having identified the upper portions 

 of the bed with the New 7 lied sandstone of Europe through the presence 

 of "vertebral" remains found at East Windsor, Connecticut, and Sun- 

 derland and other localities in Massachusetts. He still, however, 

 thought it not impossible that the lower portion of the beds might cor- 

 respond to the Old Red sandstone of Europe. It will be remembered 

 that in the American Journal of Science for 1823 he considered these 

 upper beds as belonging to the coal formation, on account of the 

 included thin seams of bituminous coals. 



"Humboldt's Essay on the Trend of Rocks in the Two Hemispheres appeared in 

 1822. 



