The Iowa plain dealer. [volume] (New Oregon, Howard County, Iowa) 1867-1895, 1877-06-22

In ii lat~r III ths inurfsuH sNufuraR.
IN. lsrof. L. ~. Whitney, ntirr al,nn,es
the insntiiri,imy ~ ihv ordinary th.nitsa
~ explain why prairirs arr n.t riis
rroachr.l nlm,l hy tlic bordering aprls,
offers the following explanation II his
own.
LET ~ intn II present ta the grnlps
iral ~i,ic III III. investigation. tn.
whole III New England anil New York.
and large pars II Ohio and lnlian,.
together wi,h tla. whola ~ Nichinnil
anl ~ Northern Wisconsin,. constitute 4
region over which lhr northern ,lriis
phenomena have bcn displayed on Il
grand sale. Consequently almost thu
whole III this arra Ii coycrl With heavy
deposits VI cnnrrc gravel nnl conrsr
buwl,lcr materials. These deposits. IL
not III thu surface, az. near IL. and thu
timer materials deposited on them. hy
nllnvinl nna other agencies. generally
form only thin covering for the cHr'r
deposits Mnrth. l,ut M va ~ Aoutli
anil west from thc region Indicated
above. W. iin,t The underlying rp'k---i'r
.lM,t ,rrk," ~ TIN Californian miners
would emil II deeply covered with lo,se
mntcrinls. ii iE tr,G, hut W. observe TINT
these ARE quite different IN character
from what the, nrr ~ the nottli ni'd
cast. W. e,inc "a u region where the
.lrift ngcnric. have been very limited IN
their action. Tho bulk Of the super.
tlciul ,letritts lns hecn formed from the
decomposition Of the underlying ro.k.
nnd this ,lrtritns Inns been Int little sliA-
tnrlAsl or moved from, its original pow.
tiun. II crrntic deposits exist. they nrr
usually deeply covered with finer nj.
terials derived from close III ln,.nl.
A grcn, urca exists In Wisconsin nild
Minnc..,tl over which not Il siugle
drift pebble har ever hcen lu'iinl, either
III the surface or M my depth l,enrafl, u.
The strata hnve become chemically .iih-
aggregated and dissolved hy sh* pcrsola.
tinn uf the rnin through them. the ralct.
reons matter llas been carried ptf III 80.
luton, nn.l there III lrtt behind ns |.
rc.i.lnum the inrolnhle matter wliiel, the
rock originally contained, aud which,
consisting largely III riliea anl silieate q
nluninn, forms by its aggregation \ sIl'.
cions nna clnyey deposit Of almost in.
pnlpnhl. ilnen i. II il this Tine material
which makes up tlm bulk of the prairie
anil; nn,l, ~ tile writer concei,ts, II IL
this iinencss which il especially ininlic,'l
10 tin growth of trccH. Exactly IN vi
ncc the Il, sircatcd lak Ia the m,lst ~
the forests gradually iilling mp will, ilncly
comminntel materials nill becoming COY.
cred with growth of gransen of Hedsrr,
which Ii not nfterwnrl cnrroncliesl on NY
trees, no matter whether thu ground ln'.
comes completely dry or whether i r.
mains moro or leHs nwampy, No We linve
The prair,ra, which have certainly never
al my time been ovcrspreal with forests,
and which would always remain IN they
ar,, provided III. climate underwent np
radical change md they werc not inter.
fcml with hy man. Il IN for the sc.e-
table physiolosint to say why this iin.-
ncss III .pil in infavorahlc 10 the growth
oi trees: II IL Tor the geulogist and physi-
cal gcogrnpller ~ vt foftl, the facts
wlicl, they may observe Within the line
III their own professional work.