The Prairies of Arkansas do not appear to have been formed all in the same _ 
manner. me So are underlaid by different sane situated at various ele- 
vations, and th Fo seo aspect differs apparently so much, that it looks as if 
a peculiar law had directed the formation of eac : Be em, 
ave explained aaincen the age ral form of the prairies, and as- 
cribed it to the agency o water. the prairies still in a state of Siero 
to ry an slow recession o water, n land is continually cover 
by low ecigna nt its on fy egetation is ‘that of the rushes and of the 
sedges. en the same land is alternately subjected to Jong inundations and 
then to dryness, during 00 me months of the year, the same plants continue to 
the borders of the lakes, or hard, cold, impermeable when it is mixed wi 
clay or muddy alluvium, = in some marshes ide rlaid by clay or shales, or 
along the banks of Bote rivers. Land ae covered with stagnant 
water ome produc ip trees, because the tre ean for their aoe i 
roots. Neit er do trees et and grow ona ¢ wien alternately covere a 
with stagnant water and exposed to dryness for ‘some months o the year. 
From nie considerations, the hw of the general formation of the prairies can 
be deduced: While a land ora part of a country is slowly passing from the state 
of esi or marsh to the pats of dry land the ae alternative ot stagnant 
water and dryness causes the vegetation of peculiar plants, which, by their 
decomposition, form a peculiar ae weve di a the Pais of the trees. 
From this general rule of formatio ich regards only the prairies of the 
oye valley} all the different ‘chiethoasiank or soci appearances of the 
asil ed. 
The praitiog of r Aaah following their vegetation and their geological 
sab eigen may be separated in ree classes: 
he prairies of the North, rscitly underlaid by cherty limestone. 
a. The prairies of the West, on carboniferous shales and clay. 
d. The prairies of the South and East, overlaying tertiary and alluvial 
formations. 
Ist. The i gees of North Arkansas mostly belong to the counties 
whieh are examin next division. singular in this fact, that 
their surface is rani avays flat, and that they are mostly placed on soft iv- 
ities or cov ng or between the ridges. They are mostly of sinall extent 
and surrounded by thickets of low trees. The compact or somewhat porous 
Subcarboniferous Limestone which they cover does not absorb water with rapid- 
ity. Hence, inthe spring, Heme percolates slowly along the slopes, taking with 
it the detritus of the stone, and tome it where its course is either stopped 
or slackened. A scant swamp vegetation igi ida there, its decomposed 
thickness under the acto of water and of s on. This soil is naturally 
Sag gives water for a part ‘of the yee. ike the pom t, which it resem- 
bles, and thus cannot sustain trees. They establish ther i 
Hoand "all around. When by successive er “eitoey of limestone de 
coarser materials are of course heaped on anks of these creeks, a few 
* Bulletin of the Society of Natural Sciences of Neuchatel vg i 
PM The orig d of the far West along the éastern base of the Rocky Mountains, 
sandy deserts, caused by the Uryness of the a 
