cin ia i 
306 Dr. Hayden on the Period of Elevation of the 
ences which gave to it, its present configuration. Some errone- 
ous statements, growing out of our limited knowledge of the 
structure of these mountain chains, may be made, but these when 
known, will be corrected. Geology is'a progressive science and 
ven our best efforts are but approximations to truth rather than 3 
1 ; : 
the truth itself. 3 
The evidence seems to me to be clear that the great subterra- © 
nean forces that elevated the western portion of our continent 
were called into operation toward the close of the Cretaceous 
epoch, and that the gradual quiet rising continued, without ! 
general bursting of the earth’s crust until after the accumulation 
of the Tertiary lignite deposits or at least the greater part of them; 
also that after the fracture of the surface commenced and those 
great crust movements began to display themselves, the whole 
country continued rising, or at least, though there may have been 
wel uture. i 
Let us, in the first place, examine some-of the barometrical 
profiles across the country from the comgery 4 river to the Pacific 
et Srertti : 
oft 
mountain elevations. Reaching the ridges 
which form the mountain crests, we at once commence a rugged ! 
and abrupt ascent. Le 
_ If we look at the profile constructed by Gov. Stevens, from 
° 58" and lon. 92° 58’ to the Pacific 
west : 
ting plain, with no disturbance of the strata of the underlying 
Paul, Minnesota, lat. 44 
so 
