438 J. D. Dana— Results of the Earth’s Contraction. 
B. Mountain-making after Archzan time on the Pacific border, within the terri- 
tory of the United States. 
(1.) At the close of the Lower Silurian, none yet known. 
(2.) At the close of the Devonian, none yet known. 
(3.) At the close of the Carboniferous age, or the Paleozoic, 
none yet known; and if none really occurred, then the con- 
tracting globe at that time, as far as U. S. N. America is con- 
cerned, must have expended its energies, which it had been 
gathering during the Paleozoic, in making the Alleghanies and 
in some minor plications along the Acadian region 
The “Great Basin,” between the Sierra Nevada on its western 
border, and the Wahsatch range on its eastern (lying along the 
meridian just east of the Great Salt Lake), contains a number of 
short ridges, parallel to these lofty border ranges, some of which 
are quite high ;* and they consist, according to King, “of folds 
of the infra-J urassic rocks”; and “it is common to find no rocks 
higher than the Carboniferous,” owing, it is stated, to the erosion 
that has taken place. It is not clear that part, at least, of the 
Great Basin plications may not have taken place before the 
Jurassic era. not, then the movements must have been in 
some way involved with those of the Sierra and Wahsatch 
regions. : 
(4.) At the close of the Jurassic, two great geosynclinals, 
which had been in progress through the Paleozoic and until 
this epoch in the Mesozoic, culminated each in the making of ® 
lofty synclinorium—one, the Sierra Nevada, some of whose 
summits are over 14,000 feet high; the other the high Wah- 
satch, a parallel north and south range. ‘ 
itney has proved that the Carboniferous and Jurassic 
rocks are comformable in the Sierra Nevada range, and that 
the close of the Jurassic was the epoch of its origin ; but direct 
proof is not yet found that the Devonian and Silurian forma- 
tions are included. The granite axis of the chain peobee 
to be Ar- 
chean, which he states are conformable also. The plications 
and mountain-making took place, as King states, cotemporane- 
* An admirable chart, giving in detail the topography of this whole region, and 
including the Wahsatch, has been prepared by Mr. James T. Gardner after careful 
ar topographical surveyor of the Exploration of the } Le 
Parallel under Clarence King, and is now ready for the engraver. Mr. King 
published thus far only brief ¢ on zical 
the volume of J. T. Hague on Mining Industry (vol. 111). He has ready for pub- 
Hication Vols. I and Il, « ipti ; . 
Report of the Survey, Vol. V, has been issued; but Vol. IV, on Zodlogy and 
remains to be completed. 
toe eee * 
