New-York tribune., 1891-08-29
GEOLOGICALl STUDIES.
A DISCUSSION BY THE SCIENTISTS IN WASH
INGTON.
THE DIFFERENT BASES FOR CoRRELATIoNs-
BIOLOGISTS TRACING THE PAST HISTORY
OF THE CONTINENT.

THE DIFFERENT BASES FOR CORRELATioNs-
BIOLOGISTS TRACING THE PAST HISTORY
OF THE CONTINENT.
TBr TELEGRAPH TO THE TKIBUHE1
Washington, Aug. 2s.-The International Geoiogeh
Congress lost Its poyglot character to-day as All tho
speakers used English. The topic OF the day was
"The correlation OF geological formations ana tho
same subject win be continued tomorrow Professor
Gilbert opened the discussion by presenting the follow
ing scheme Of methods Of correlatng strata Pys
means OF eorreatlon-1 visible continuity z. htho-
logic similarity g. similarity Of sequence T. physcai
breaks ., relation TO physical events O, comparative
change. Biotc means of correlatlon-7, Matching by
species; 8, matching by genera and families D, diver
gence from status at fixed date 10, relation TO climate
Mr. Gilbert said that the first step m chronological
arrangement Is visible sequence the second Is correla
ton. The great body Of correlation is based upon the
third DIVISION similarity Of sequence The triasSc
Of the United States correlated by physical
breaks Examples of correlation by relation to ply sca
events formations in Utah. correlated with certain
ake-beds, also on the Eastern seaboard base level
plains correlated with Others in the Piedmont and
Appalachian region. Aluvial. httoral and subaqueous
deposits may be thus compared. Comparison by Bioic
methods, or typical life FORMS explained in detail,
and the following canon Of comparison was enuncLted
"The value OF species for purposes of correlation is
nversey az its range In time, and directly Its range
I'm space" Insects not of use, because OF their
penshability. Marine mofusos are most valuable.
Fucolds have too great range in time, while vere-
brates though valuable because OF their narrow range
in time have their usefulness limited by their
range in space.
Mr.. Won Zittell emphasized the statement as to the
uselessness Of plants and the OF marine mouscs
Baron De Geer suggested that more attention be paid
to the number Of individuals found OF each species.
Professor Marsh, agreeing as to the importance Of
marine mOlluses where they be used. said that
from mesozoic up vertebrates the best criterion,
because of the lack of invertebrates, especially OF
marine forms. He recspitulated his classification Of
formations vertebrate fossils, found in the
Rocky Mountain regions. At the very beginning Of his
explorations there he found that the methods he
learned in Europe were inadequate, and in 1877 he
proposed new system to the American Association
for the Advancement of Science, which was further
modified in 1884, and again revised and corrected up
TO date He now classifes three horizons In the
jurasslc the lower one fresh water the Others marine
the third being characterized by the atlantosaurus
Above this cretaceous Dakota Colorado and Fox
Hin beds Then the Laramie formation closes the
mesozoic Above this, in the eocene, mammals first
became dominant. The coryphidOn correlates this with
the eocene Of England. Then come the Green RIVER
beds, with helobatus democeros beds and placdern
beds next the nuocene characterized BY presence OF
the brontoherlum, then the oreidon, then mohippus
In the afternoon Professor walcot spoke of the
value of plants In cOTelang coal measures and some
other formations, Professor HngneS ucScrIeu somo
exceptional conditions and difficult uncomfortable
deposits, suggesting a solution Of certain problems
relative to the old and new red sandstone. Major
Powell explained the combination Of physical and
botc comparisons employed successfully in the Geolog
cal Survey.
Professor MCGEE pointed out that in the coastal
plain Of the United States the formations and land
forms best correlated on physical basis FOSSILS
are not lacking-ndeed, one formation yields bones
OF jurasc dinausaurus, leaves of cretaceous plants
and shells Of quatenay moluscs as classed by dlfer
ent paaeontoogsts, but physical correlation has en-
abed the geoOgst to interpret the past history OF
considerable part Of the continent so definitely that
the geography and the topography of the several
periods may be mapped with fair degree of accuracy
From this physical history the geographic distribution
of animals and plants during past ages may be ascer
tained and thus palaecntolOgy may be placed on a
higher plane.
Professor Davis explained the formation OF the coast
region from Newly westward to the Alleghanles.
This region nearly plain, afterward ele-
waited toward tie west and the valleys were made by
denudation. The Hudson River valley IS tertiary
denudation, and the channel of the river IS POSTER
tiary The denudaton of this region has been slDaer
Professors Caypole and Van Iilse continued the us
The bulletin Of the Geological Survey, which has
heen distributed to members of the Congress is the first
of series Major Powell Informed the Congress that
seven or eight would soon follow. The present
volume is entlted Correlation Papers, Deyonan ana
Carboniferous,' and is edited by Professor H. s. Will
iams Of Cornell University. -, ~
The Congress spent the evening In vlSlung the Ma
tiOnal Museum.