and great differences in the outline of the ice-sheet had
occurred.

During this retreat, and for a period after the ice had
retreated sufficiently for the development of drainage
systems to begin, considerable portions of the newer-
drift area were apparently occupied by water, either
as lakes or as sluggish streams. Deposits bear-
ing evidence of the presence of water are found in the
Kankakee basin, where a belt of sand several miles in
width occurs along the entire length of the river. There
are also notable accumulations of sand along the Illinois-



83

Vermilion, extending back several miles from the bluffs
of the stream.

Much of this newer drift is covered by a thin sheet of
loess-like, pebbleless, silty material. It is not nearly so
think nor so continuous a deposit as that covering the
earlier drift. Where it is thickest, and most closely re-
sembles the loess (in Bureau creek drainage area, north
of the bend of the Illinois), it attains a depth of about
eight feet. It is also notably present in central Illinois,
from Peoria southeastward to Bloomington, covering not
only plain tracts, but also some of the highest ridges in
that portion of the State (those near Bloomington). It
has here a thickness of but three to five feet, and is
less pervious to water than typical loess. Along the
outer portion of the newer drift in central and eastern
Illinois, and low-lying districts in northeastern Illinois,
there is not enough of this silt to conceal surface boul-
ders, while over large districts the pebbly clays of the
glacial drift are at the surface, and constitute the soil.
This silt is probably, in part, a water deposit, but in
certain cases its presence seems difficult of explanation
on the theory of submergence, either general or local,
and it may be necessary to call in the supplementary
agency of wind in explaining its distribution.

After the ice sheet had withdrawn from Illinois the
outlet of Lake Michigan, for a long time, was south-
westward, across the site of Chicago to the Desplaiues
river. The lake then, for a time, stood about 55 feet
above its present level, and formed a well defined beach
at this stage. It covered not only the present site of
Chicago, but extended west, slightly beyond the Desplaines
river, to Maywood and LaGrange, and south, beyond
the Calumet, to Conley's and Homewood, Illinois, and
Dyer, Indiana. Blue Island Ridge stood above the sur-
face of the lake, and so did an elevated tract southeast



86

of Willow Springs. (See Soil Map). As the lake subsided
from this high level to the present, it halted sufficiently
long to form well defined beaches at two levels one beach
being about 35 feet, and another 15 to 20 feet, above the
present level. The low gravel ridges west and north from
the Exposition grounds, were formed at the stage when
the lake stood about 15 feet above the present level.
They do not mark the extreme west shore of the lake,
but were formed as bars some distance out from the
shore, the west shore at that time being in the western
part of Chicago. These bars, however, prevented wave
action in the district west of them, and no beach depos-
its of consequence occur back of them. While this district
was occupied by the expanded lake, soils were forming
in the remainder of the State. This district from which
the lake has recently withdrawn is, therefore, the young-
est part of the State. According to estimates made by
Dr. Edmund Andrews, based upon the present rate of
transportation of sand past the Chicago piers, Lake
Michigan has occupied its present level for less than 6,000
years. This estimate accords well with estimates on re-
cession of falls in post-glacial time, made by Prof. N. H.
Winchell and Mr. G. K. Gilbert.

II. Glasses of Soil.

It will be readily understood by anyone that in any
given region there may be deviations of more or less
consequence from the prevailing type of soil deviations
which may affect, to some extent, the value of the soil.
Often an exceptionally good farm lies in the midst of an
otherwise inferior agricultural district, or a poor farm may
lie in a district where the land is of superior quality. Such
deviations, even where known, cannot be represented upon
a map of the scale here used, nor given individual atten-
tion. Only general classification can be made, and



87

approximate boundaries indicated. It is left to those
interested in any particular district, to note the excep-
tions and fill out the outline.

The classification of soils which seems to best serve our
purpose is based mainly upon physical characteristics.
The following classes are represented: (1). Kesiduary
soils, or soils formed from the underlying rock. (2).
Stony or glacial clays. (3). Gravelly soils. (4). Sandy
soils. (5). Loess or silt rapidly pervious to water. (6).
Silts slowly pervious to water. (7). Fine silts nearly
impervious to water. (8). Peaty or organic material.

(1). Residuary Soils. These soils show variations
which correspond in a rude way with variations in the
structure of the rocks, from which they are derived, there
being in regions underlain by shale or limestone a more
compact and adhesive soil than in sandstone regions,
while each class of limestone has its own peculiar soil,
and soils derived from shales range from stiff clay to a
very sandy material. A complete analysis of the nature
of the differences displayed by the several classes of
residuary soils has not been made. With proper rota-
tion of crops these soils constitute a fertile portion of
the State, otherwise they become exhausted sooner than
soils formed from glacial drift.

(2). Stony or Glacial Clay. Under this class is included
the weathered surface of the drift-sheet wherever it was
unaffected by water action during deposition, or was
not subsequently coated by silt, sand, or other material.
It includes the greater part of the surface of the newer drift-
sheet between the Shelbyville moraine and Lake Michi-
gan, and much of the earlier drift-sheet in the districts
north of the sandy belts of the Green and Rock river
valleys. The soils are very productive, being composed
of a varied rock material, a large percentage of which
is in a fine state of division. Where the surface of the



88

country is rolling all classes of grains and fruits suited
to the 'latitude will flourish. On flat districts corn and
grass are exceptionally productive.

(3). Gravelly Soils. Gravelly soils are varied in their
method of deposition, occurring in lake beaches and
along streams, in drift knolls and ridges, and beneath
plains not now occupied by streams. In the last-named
situation the plains are so related to the drift ridges as
to show that they were occupied by glacial waters.

The beaches have generally a poor soil, but the gravel
terraces along streams, especially those of glacial age,
have as a rule a capping of loam several feet thick,
which renders them productive. The same is often true
of gravelly knolls and ridges. On the whole, the soils
underlain by gravel possess more fertility than do the
sandy soils. This superiority is, however, due to the
capping of loam which constitutes the soil, or, as in the
drift knolls and ridges, to an admixture of clay or earthy
material with the surface portion of the gravel. The
coarse fragments in the gravel can furnish but little
sustenance to crops, although, by weathering, the stones
may yield rich material to the soils and furnish a greater
variety of plant food than could be obtained from a
siliceous sand.

(4). Sandy Soils. The sandy soils, though much alike
in structure, are varied in their methods of deposit.
They occur in the beaches along the borders of Lake
Michigan, in the valley bottoms of the main streams, on
the bluffs and along the borders of the streams which lead
away from the newer drift district, in basins within the
newer drift district (as the Kankakee and Illinois- Vermil-
ion), and to a limited extent in the drift ridges (moraine).
There is also an extensive development of sand in north-
western Illinois, in the Green river basin and the border-
ing districts, as far north as northern Whiteside county.



89

Where the sand is of medium to coarse grade it is usually
rather barren, but where fine, as in the eastern portion of
the sandy belt bordering the Illinois in Tazewell and Mason
counties, it is very productive. Within the districts noted
upon the map as sand-covered, there are more or less ex-
tensive tracts of wet, mucky land. This, where artificially
drained, has often proved very productive. There are
districts where the loess assumes a sandy phase, but in
these places the sand is very fine, so fine that individual
grains can scarcely be recognized, and the fertility is
about as great as in the typical loess.

(5). Loess or silts readily pervious to water. This class
of silt is confined mainly to the borders of the principal
streams of the older drift district, though there is a
somewhat extensive development within the newer drift
area in the Bureau creek basin, as noted above. In
southern Illinois the loess graduates into white clay in
receding a few miles from the Mississippi, Ohio and Wa-
bash rivers; in western Illinois into the slowly pervious
silt described below, and in the extreme north it thins
out, and the residuary clays come to the surface.

The loess is so well known as scarcely to need descrip-
tion. In this State it is occasionally fossiliferous and
calcareous, but as a rule, fossils are rare, and lime is a
subordinate element. The chief material is silica in a fine
state of division, but with the silica are rock fragments
of various kinds, especially of crystalline rocks. The
loess is so porous that roots penetrate readily to a great
depth (2530 feet or more). It yields fair crops of all
kinds, but is especially valuable for fruits, both orchard
and small fruits. The physical condition of porosity
seems to be the chief cause for the superiority of the loess
and the other pervious silts, over the white clays and
finer silts. Nothing has been found to indicate that the
former contain a better supply of plant food than the



90

latter, while the fertility of the latter is made certain by
the rich growth of such crops as will flourish in a com-
pact soil.

(6).. Silts slowly pervious to water. This class of silts
embraces the rich black soil district of the western por-
tion of the State. The southern boundary lies near a
line connecting Alton, Litchfield and Pana. The eastern
boundary of the main district may be placed at the bor-
der of the newer drift. The northern boundary is near
the south border of the Green river basin, while the west-
ern boundary is found in the loess that borders the
Mississippi. Through this district there passes the belt
of typical loess which borders the Illinois, a belt only a few
miles in width. Aside from this main district, there is
considerable silt of this class between the Rock and Mis-
sissippi livers, in northern Illinois, capping the earlier
drift sheet.

On the newer drift, as stated above, silts slowly per-
vious to water cover large districts in central and eastern
Illinois to a depth of several feet. In northeastern Illi-
nois, such a silt capping is not a- common feature.

Wherever silts of this class occur the vegetation is
usually prairie grass, and there is a blackening of the
soil by humus to a depth of several inches, often two
feet or more. This class of silts gives rise to a highly
productive soil One which will yield fair returns even
under most careless methods of farming. Corn and
grass are the staple products, but other crops have a
fair yield.

(7). Fine silts, nearly impervious to water. These silts
are of two classes, white clay and gumbo. The first
class covers the uplands of much of southern Illinois.
The second is common in portions of modern river val-
leys, remote from the current and subject to overflow
a periods of extreme high water, and has great extent
along the Illinois and Mississippi river bottoms. A less



91

compact silt, found in river bottoms, is known as
potato land.

The white clay is a pale colored deposit scarcely at all
blackened by humus. It covers the greater part of the
State south from a line running eastward from Litch-
field, Illinois, to the Wabash valley, near Terre Haute,
Indiana. It is so compact that much of the water
stands on the surface until removed by evaporation,
while in seasons of drouth scarcely enough water rises
from below to supply the loss from evaporation. In
the southeastern portion of the State there is, however,
a looser soil less easily influenced either by excess or de-
ficiency of rain. In that part of the State the surface is
hilly and the drift so thin that the rock, in many
places, comes sufficiently near the surface to have be-
come uncovered by erosion and deeply weathered in
post-glacial time.

There are extensive districts with very flat surface
where the white clay soil is underlain at a depth of a
few inches, with a ferruginous crust or ochery clay,
which is exceedingly refractory, giving very slow access
to air or water. In the greater part of the region, how-
ever, this crust is either absent or is so low down that
it does not seriously affect the soil. With the exception
of corn, which is liable to be injured by autumn drouths,
the leading crops of the State do fairly well. Wheat
yields as well as anywhere in the State, while orchards
and small fruits bring very profitable returns. The soil
needs careful attention, but there is every indication
that where properly cared for it will become as profit-
able for agriculture as the soils which now enjoy a bet-
ter reputation.

The surface of this white clay district is nearty equally
divided between forest and prairie. The former borders
the streams and the latter occupies the divides. Here,



92

as well as elsewhere in the State, the causes for the re-
striction of the forest are not fully understood.

(8). Peaty and Organic Soils. Such soils occur in
basins or in poorly drained tracts, where rank vegeta-
tion becomes submerged at certain seasons and is thus
prevented from atmospheric decay. This class of soils
is much more abundant in the northern one-third of the
State than further south. Peat bogs occur, however,
south of the center of the State.

Many bogs are underlain by shell marl as well as by
peat. The marl is seldom sufficiently pure or abundant
to be used in the manufacture of lime.

In many instances the bogs, when drained and the
peat given time to ripen and become warm, yield large
crops of potatoes and other garden truck. Wheat or
other crops requiring mineral food in the ripening of
their grains, can scarcely be expected to grow on such
soil until it becomes charged with earthy material by
natural or by artificial processes.



REPORT ON THE EXAMINATION OF SOME
SOILS FROM ILLINOIS.



BY MILTON WHITNEY.



fOILS are derived from the disintegration oi rocks.
They consist of minute fragments of the rocks or of
the minerals which compose the rock, or of some
other minerals which have been formed by the chemi-
cal changes constantly going on in the soil. These
small particles of mineral matters, although they seem
to be very compact and continuous in the soil, have
minute spaces between them, into which the water can
enter. Soils contain, as a rule, about fifty per cent, by
volume, of empty space, that is, a cubic foot of soil will
contain about half a cubic foot of space, and will absorb
about half a cubic foot of water. Coarse grained sandy
soils usually have the smallest amount of empty space
and fine grained, heavy clay soils, which really weigh
less per cubic foot, have considerably more empty space,
and will hold more water. The smaller these spaces are
and the more uniform they are in size, the slower will
water move through them, but the soil will have greater
power for holding water and for drawing water up from
below. This is the case in strong clay soils. There is a
larger amount of space for water to be held in, and the
mineral fragments composing the soil are extremely
small, so that there are a large number of them in a
cubic foot of soil, and the spaces between them are very
small, making the soil very retentive of moisture, be-
cause the rainfall can only pass down through it very
slowly and it can be drawn up again to the plants with
considerable force. It should be noticed here, also, for

93



94

this is probably very important in the consideration of
these fertile western lands, that the presence of large
amounts of organic matter will have the same effect in
making the soil retentive of moisture as a large percent-
age of clay, but if, through constant cultivation the
organic matter is oxidized and used up, the lands will
become more and more sandy in texture and less pro-
ductive. Therefore, a heavy clay soil is stronger, more
certain and more lasting than a virgin soil, depending
for its retentive powers and its fertility upon the ac-
cumulation of organic matter.

These mineral matters composing the soil contain cer-
tain chemical elements required by plants, such, for ex-
ample, as potash, phosphoric acid, lime, silica, alumina,
etc. All soils, even very barren ones, contain at least a
ton of each of these elements in one acre, to a depth of
one foot, and they usually contain from two to twenty
tons of each of these plant foods. With this vast quan-
tity of food material the barrenness of soils cannot be
due to the lack of plant food, and the deterioration of
lands cannot be due to the loss of plant food, for it
would be impossible for crops to remove so much plant
food as this in the few years ib takes for a soil to be-
come worn out under improper methods of cultivation.

The prevailing ideas of plant nutrition have been based
mainly upon the chemical composition of soils. When
it was found that the chemical composition of a soil
and plant did not show what was lacking in the soil
for a large crop, it was held that only a small part of
the plant food in the soil is at any one time in a form
of combination which is available to plants; that the
available plant food never accumulates as such in the
soil, but quickly reverts to more insoluble forms, which
are unavailable to plants. According to this idea the
exhaustion of soils by continued cropping is due to the



95

actual loss of available plant food, removed by the crop
or converted into an unavailable form by chemical
changes in the soil. The chief use of fertilizers is to sup-
ply the plant with food which the soil fails to furnish.
The reason certain plants do better on certain kinds of
soil is assumed to be due to the fact that plants vary
greatly in their powers of gathering their food from the
soil and air, and that thus a rye plant would do well
on a soil too poor to give a good yield of wheat.

Our investigations on the Maryland soil seem to show,
however, that the texture and the physical conditions
of the soils are of more importance Than the chemical
composition. It appears that under favorable condi-
tions of moisture and temperature plants can readily
gather sufficient food material from nearly all soils, but
if these conditions of moisture and heat are changed the
development of the plant will be greatly changed and it
will take up more or less food from the soil. Soils differ
greatly in their texture, that is, in the amount of sand
and clay which they contain, and, as we have seen, this
controls very largely the supply of moisture which they
can maintain for the crop, with a given amount of rain-
fall. If there are four inches of rainfall a month a coarse
sandy soil will allow most of this to run through very
quickly, so that there may not be more than 5 or 6 per
cent of water held in the soil for the crop, or say about
100 tons of water per acre one foot deep, and when this
water is used up the soil has comparatively very little
power to draw up more water from below for the use
of the crops. With a compact clay soil, on the other
hand,- 1he water passes downward very slowly, and the
soil will maintain about 18 or 20 per cent of its weight
of water for the crop, or about 400 or 500 tons of
water per acre one foot deep. In a dry season, also,
the clay soil has more power of drawing up water from
below and maintaining this supply. If a florist should



96

give a plant four times as much water as he gives
another plant of the same kind, the two plants would
develop very differently, and he uses this constantly to
produce any kind of development he desires. If it is de-
sired to have the plants flower or fruit, the soil is kept
rather dry and cool. It' it is desired to produce large,
leafy plants, the soil is kept much wetter and warmer.
To have equal success with different kinds of plants the
amount of water must be carefully regulated according
to the needs of the plants. Some plants require a much
more abundant supply of water than others. This con-
trol of moisture and temperature is far more important
than the mere chemical composition of the soil.

The texture of our various soils being different, they are
enabled to maintain a variety of conditions of moisture,
and they partake somewhat of these artificial conditions
in a green-house, the conditions in each of the soils
being best suited to the needs of certain classes of plants.

The amount of moisture which a soil can maintain
for a crop, under given climatic conditions, will depend
mainly, (1) upon the amount of space in the soil in
which water can enter; (2) upon the extent of subdi-
vision of -this space, that is, upon the number of grains
of sand and clay there are in a given volume of soil;
(3) upon the arrangement of these grains, for, as al-
read3 r remarked, if the grains are symmetrically ar-
ranged, so that the spaces shall all be of uniform size,
water will move through the soil much slower than if
the spaces are of very unequal sizes; (4) upon the
amount and condition of the organic matter in the
soil. The grains of clay are so exceedingly small that
their number vastly exceeds the number of the grains of
sand and silt, so that the percentage of clay practically
determines the extent of subdivision of the space, and
it is thus the most important ingredient of the soil.



97

The mechanical analysis of soils consists of separating
out the different grains of sand, silt and clay. Of these
the most important is clay, for reasons just given. Be-
fore giving the mechanical analysis of the Illinois samples
it will be interesting to say a few words as to the origin
of these soils, for this has some bearing upon the texture.

There is only a small area of the old crystalline rocks
in this country. Most of these old crystalline rocks
have been disintegrated by the various forces concerned
in the decay of rocks, and the material resulting from
the disintegration of the rocks has been carried off by
water, wind and moving ice, and deposited elsewhere as
"sedimentary" material. The Illinois soils are of this
sedimentary nature. The older crystalline rocks have
long ago been worn away, and have been covered with
this sedimentary material. When the original crystal-
line rock disintegrates grains of all different sizes may
be produced, from coarse gravel to the finest grades of
silt and clay. If this material is carried off by water
and deposited near by there is likely to be a variety of
soils formed, having very different textures. Some will
have more of the coarser fragments, and others will
have more of the finer material, according to the dis-
tance they will have to be carried and the circum-
stances under which they are deposited. When the
material has to be carried further the deposits are more
likely to be of uniform size.

In Maryland we have a broad area of these old crys-
talline rocks, in what is called the Piedmont Plateau,
with mountains on one side, made up of sedimentary
material, and still more recent sedimentary deposits of
the coastal plain on the other side, which has not yet
been consolidated into rock. All of these sediments had
been laid down within a comparatively short distance of
the old crystalline rock from which the material came.
We have representatives of all the geological formations,



98



from the old crystaline rocks down to the most recent
quarternary deposits. As these have been laid down near
the source of supply from which the material was de-
rived, and have not since been modified by glacial
action, it happens we have a great variety of soil forma-
tions, and it is both interesting and instructive to see