27s Th( Aiiitl'ivatl (JcoliMJixt. November, IHOl 
SitUniriitd ry /)ii>ii.si/s mit of irjiicli Moiiittit! n-lin ih/i x Jiarc Ixfii 
1)11 lit II 1 1 r.rtriiif DVir I <isf Ai'<'iis. 
'I'lu' (U'posits out (if wliicli liivMt iiiouiitaiii'i'Miiucs have Ir'C'II 
elaborated hv foklinos. intrusions, and ui)-h('a\als arc not eon- 
fined to the ranges and their innneditite neighborhood, but extend 
over vast areas. Speaking generally, modern geological investi- 
gation goes to prove that the thickest deposits lie, or have lain, 
towards the axes of the chains, though they mav have l»een de- 
nuded from tlie actual axes*. Beyond the more folded and dis- 
tnrlicd portions of the chain which often, so far as the newer 
sediments are concerned, lie on the Hanks, the strata take on 
more gentle curvatures until, as in the case of the Urals, the Ap- 
palachians, and elsewhere where ol)servable. they Ix'coinc nearly 
horizontal, or only have dips due principally to faulting. 
The Tertiary and (^retaceous rocks extend from the Alps to the 
Caucasus and across the Mediterranean to the African coast, and 
may lie far beyond, as little is known of the geology of that part 
of the continent. They reappear in the Himalayas, and may be 
*Mr. Arthur Winslow, State Geologist of Missouri, in a paper just 
published in the "Hulletin" of the Geological Society of America, en- 
titled "The Geotectonic and Physiographic Geology of Western Arkan- 
sas" (vol. ii. pp. 22.')-242), has applied the principles enunciated in the 
"Origin of Mountain-Kanges" to the e.xplanatiou of an area in the 
Western part of the state tributary to the Arkansas river, 100 miles long 
in an east and west direction by fifty miles broad in a north and south 
direction. It is shown in an admirably concise and clear manner that 
the system of parallel interlocking anticlines and syncliues having a 
general a.xial direction east and west is essentially Appalachian in char- 
acter; that the Carboniferous strata of which they are composed in- 
crease in thickness from Missouri southwards into Arkansas; that the 
lateral movement has come from the South, and that the thickest strata 
are the most tle.xed. Mr. Winslovv shows — a point that I have strongly 
insisted upon as characteristic of anticlines— that these geological 
features are elongated canoe-shaped domes having (piacjuaversal dips. 
He considers that the expansion of the lower layers of rock produced 
hj' the rising of the isogeotherms and their consecpient protrusion in the 
form of anticlinal cores has fractured the apices of the arches, and thus 
e.xposcd the upper layers to energetic denudation. lie infers also that 
the developed sections of such foldings are no measure of the original 
horizontal length of the beds — a principle I have strongly upheld, and 
which is being conceded by most geologists who have studied mountain- 
structure. The district seems to iie one in which the tirst jtrinciples of 
the dynamics of mountain-building can be well analyzed, as there is not 
such a c(nnplcxity of causes to l)c considered and discounted as in the 
more colossal disturbances of the great mountain-ranges of the world. 
A few careful studies of moimtain physiography such as this l)y geolo- 
gists who have the opportunity and are etpiipped with the necessary 
physical knowledge would be of infinite service. 
