A404 Emmons on American Geology. : 
the Taconic rocks as Mr. Hall many years ago made known, 
none other than these same strata disturbed and partially ors 
See also some remarks on the Taconic System, by H. D. Rogers, 
this Jour., 1844, xlvii, 151, and T. S. Hunt, Proceedings of the 
American Association for the Advancement of Science for 1850, 
p: : 
The published results of the Canadian Survey show that the 
Green Mountain rocks as they escape from the limits of the al- 
tered district exhibit the characteristic fossils of the*Hudson 
River group, whWe the white marbles of Rutland and Missis- 
quoi, as already stated, afford the fossils of the Trenton limestone 
in their northern and southern prolongations. It has moreover 
been shown that the auriferous veins are not confined to the rocks 
of the Champlain division, but extend into the overlying slates. 
All these facts have been’ for years before the scientific public, 
and yet Mr. Emmons tells us, that the nnFiferens rocks are inferior 
to the Date System. adds ; 
» * There evidence that the Lower Silurian are metamorphic 
rocks sity obeiais: the gold of the country. * * | entertain 
the opinion that we have no facts which Seiatitis a doctrine that the 
rocks of the Blue Ridge are altered Hudson River sandstones and 
shales, and yet the Blue ‘Ridge, which is auriferous, is identical with the 
Green mountain range.”—p. 165. 
Mr. Emmons conceives that the Taconic and Champlain rocks 
west of the Green Mountains are wedge-shaped masses, W ich 
in a breadth of a few miles are reduced from a thickness of 
several thousand feet to nothiig, and it is along the overlapping 
edges of these extraordinary formations, that he fixes his ‘line 
of weakness,” Which Someannne to the imaginary line of fracture 
and disturbance. Comment upon this is unnecessary. 
The detailed: oman of the hydroplastic rocks is not gived, 
but we have, to compensate for this deprivation, some eighty 
pages devoted to mines and mining, which we can only say are 
worthy of the author. We pass over his crude notions about the 
theory of metallic veins, and the economics of mining, expressed 
in his usual style, and shall confine ourselves to pointing ent some 
two or three errors. The iron ores of the Laurentian rocks are 
described as forming veins, while they in all cases form beds in- 
terstratified, with limestone and gneiss, and afiected by all. the 
undulations of the accompanying strata. The drawings given 
by the author, (pp. 140-150,) are sufficient to illustrate this, and 
to prove the incorrectness of his view, At p. 141 he attempts 
to explain the position of the iron by supposing that the s 
ones been folded since the formation of the veins. 
4 1e lead mines of Wisconsin and Iowa are said by Mr. Em- 
18 to. belong “to the Cliff limestone, the lower part of. which 
alent to the Niagara limestone of New York.” . This is 
or which was corrected some years ago by Mr. Hall, 
