Full text of "Coal, its properties, analysis, classification, geology, extraction, uses and distribution"

DEFT*

ITS PROPERTIES, ANALYSIS, CLASSIFI

CATION, GEOLOGY, EXTRACTION,

USES AND DISTRIBUTION

ELWOOD S. MOORE, M.A., PH.D.

PROFESSOR OF GEOLOGY AND MINERALOGY AND DEAN
OF THE SCHOOL OF MINES OF THE PENN-
SYLVANIA STATE COLLEGE.

NEW YORK

JOHN WILEY & SONS, INC.

LONDON: CHAPMAN & HALL, LIMITED

IQ22

BY
ELWOOD S. MOORE

TECHNICAL COMPOSITION CO.
CAMBRIDGE, MASS., U. S. A.

PREFACE

This work has been prepared in an attempt to satisfy the demand
for a handy volume on coal. There already exists a very valuable
literature on this important subject, but it is so voluminous and
scattered that much of it is not accessible to the average reader. Many
of our older works need revision because of new discoveries in the
study of coal, such, for example, as the practical application of the
microscope in the determination of its physical character and the
discovery of more refined chemical processes for determining its
chemical properties. The great advances in extracting coal from the
earth by mechanical means and in the cleaning and coking of the
products of the mine also make it necessary to bring new processes
to the attention of the public.

There are so many different phases in the discussion of a subject
so broad as this that details regarding many matters must be omit-
ted in a one-volume work, and readers desiring detailed descriptions
of machines or complicated processes must consult works dealing
with those matters alone. While many topics are fully dealt with
in this text, such as the properties, the origin, the uses and the gen-
eral distribution of coal, some others as mining machinery, and de-
tails of distribution and character of local coal deposits can be treated
only in works of several volumes. It is hoped, however, that the
data presented will serve, for ready reference, those who make fre-
quent use of a work of this type.

I wish to take this opportunity of expressing my appreciation to
those who have so generously contributed to this work. My thanks
are specially due to Dr. H. Ries of Cornell University, at whose sug-
gestion the preparation of this text was undertaken, for suggestions
and the use of photographs and cuts. I am also particularly obli-
gated to my friend, Professor A. Lacroix, Secretaire perpetuel de
1' Academic des Sciences, Paris, for many favors, such as access to the
library of the Academy and to valuable collections, including Ren-

iii

469107

IV PREFACE

ault's slides on which he made his original study of bacteria in coal.
The late Dr. Charles R. Zeiller kindly placed at my disposal his works
on plant fossils and the coal basins of France, and Monsieur Peyerim-
hoff de Fontenelle, President, le Comite Central des Houilleres de
France generously presented me with a copy of the splendid work,
Atlas General des Houilleres, by E. Gruner and G. Bousquet. Dr.
Aubrey Strahan, Director of the Geological Survey of England and
Wales kindly supplied an advance copy of one of his works in addition
to other original data. My thanks are due also to Dr. D. F. Mc-
Farland, and to Dr. J. B. Hill of the Pennsylvania State College,
for criticism of the chapters dealing with the chemistry of coal and
with paleobotany; to Professor A. L. Kocher for retouching photo-
graphs, and to several of my students who aided greatly in copying
diagrams, sections and other material.

Although acknowledgment has been made in the text to those
from whom photographs and plans have been received, I wish to
mention particularly the officials of the Twelfth International Geol-
ogical Congress, Dr. F. D. Adams, President, who kindly granted
me permission to republish the various maps in the report on the
Coal Resources of the World. I am also indebted to Coal Age, the
Barrett Company, the Delaware and Hudson Company, the Koppers
Company and the Semet-Solvay Company for the privilege of re-
producing illustrations. Photographs or drawings were generously
contributed by Dr. R. Thiessen of the United States Bureau of Mines,
the Director of the United States Geological Survey, Dr. E. C. Jeffrey
of Harvard University, Dr W. R. Crane, Mr. Francis Harper, the
Hillman Coal Company, the Sullivan Machinery Company, the
Bethlehem Fabricators, the Ebensburg Coal Company and Mr. John
Bevan of Pottsville, Pa. In addition to those persons and organiza-
tions specifically mentioned, there are many of my friends and col-
leagues who have furnished information which has been very helpful,
and their interest and aid have been much appreciated.

ELWOOD S. MOORE

STATE COLLEGE, PA.
October 27, 1921.

CONTENTS

CHAPTER PAGE

I. THE PHYSICAL PROPERTIES OF COAL i

II. THE CHEMICAL PROPERTIES OF COAL 18

III. CHEMICAL ANALYSIS OF COAL 40

IV. VARIETIES AND RANKS OF COAL 82

V. THE CLASSIFICATION OF COALS 105

VI. THE ORIGIN OF COAL 123

VII. FOSSIL FLORA OF THE COAL-FORMING PERIODS 178

VIII. STRUCTURAL FEATURES OF COAL SEAMS 214

IX. PROSPECTING FOR COAL AND THE VALUATION OF COAL LANDS 238

X. MINING OF COAL 264

XI. THE PREPARATION AND USES OF COAL 299

XII. THE GEOLOGIC AND GEOGRAPHIC DISTRIBUTION OF COAL 328

XIII. THE COAL FIELDS OF THE WORLD AMERICA 336

XIV. THE COAL FIELDS OF THE WORLD EUROPE AND ASIA 407

XV. THE COAL FIELDS OF THE WORLD AFRICA AND OCEANIA 438

COAL

CHAPTER I
THE PHYSICAL PROPERTIES OF COAL

Introduction

History. The first mention of coal in literature dates from the
fourth century, B. C., but so rapidly has its use developed that it
has become one of the most important among all commercial factors.
The enormous production of approximately 1,478,000,000 short tons 1
for the year 1913, the last year of normal production before the great
war, indicates how useful a commodity it is to the world. This
output reckoned at the average price of the coal, as sold at the mine
throughout the United States for the same year, would reach the sum
of $1,965,740,000, while if it were computed at the price prevailing
in England or France it would be from nearly two to two and one-
half times this amount. Scarcely any home or industrial concern
among white races can exist without its use, directly or indirectly,
although as recently as the reign of Henry II of France it was con-
sidered so objectionable a fuel that the smiths in Paris obtained a
special license or paid a fine for using it. There were regulations
against its use in many of the cities of Europe during the seventeenth
century although it began to enter actively into trade in England
about the thirteenth century. Mining did not, however, become very
extensive until after the invention of the steam engine. In America
the first bituminous coal mining began in Virginia in 1787 and the
first recorded shipments of anthracite were made about 1805, although
anthracite was discovered about the year 1762, and bituminous coal
in 1679. The earliest records of production of bituminous coal in
this country date from 1820, when 3000 tons were produced. In
1814 there were 22 tons of anthracite recorded. The million- ton

1 Mineral Resources, U. S. Geol. Survey, 1914, Pt. 2, p. 639.

PHYSICAL PROPERTIES OF COAL

mark was first passed for anthracite in 1837 and for bituminous coal
in 1850.

History shows that no country has reached an eminent industrial
position which has not had large supplies of coal within its borders
or had ready access to them. Reference to the prominent nations of
the present day proves that coal and iron have been two essential
factors in their development.

It has been said that the Chinese knew the use of coal to a slight
extent before the Greeks did, but the first definite record of its utiliza-
tion is found in Aristotle's Meteorology. 1 Speaking of the combustible
bodies he says, "Those bodies which have more of earth than of smoke
are called coal-like substances." Theophrastus, a pupil of Aristotle,
and Pliny both mention this substance and its use by the smiths.
The coal mentioned in these writings was evidently all of the brown-
coal variety, and it came from Thrace in northern Greece and from
Liguria in northwestern Italy. It thus became known to the ancients
as Thracius lapis and gemma Samothracia, while jet which came from
Lycia in Asia Minor, was called Gagates after a river in that region.

The word coal, as now used, is derived from the Saxon col. It
was always cole in English until sometime in the seventeenth century,
and coal then referred to charcoal as that term is now employed. At
the present time the term coals is employed in two senses, one meaning
glowing fragments of some combustible substance and the other the
different varieties of the material known in a general way as coal.
The Germans use for coal the term Steinkohle and the French speak of
it as charbon or charbon de terre.

Coal a rock, not a mineral. Coal is the term applied to vegetal
matter with varying amounts of mineral matter and with or without
small proportions of animal matter, which through geological processes
has become so changed by loss of volatile constituents that it is more
or less compact and dark in color. It burns with comparative slow-
ness and decomposes slowly in the atmosphere. It has a variable
chemical composition and it is not homogeneous. It grades into peat,
and differs from that substance in composition chiefly in the smaller
percentages of water, oxygen and volatile hydrocarbons which it
contains. It is frequently spoken of as mineral coal 2 and in the

1 Book IV, Chap. 9, Sections 36-37. (French translation by B. S. Hilaire.)

2 Dana, E. S., System of mineralogy, 6th ed., 1892, p. 1021.

INTRODUCTION 3

United States coal lands are classed under the division of Mineral
Lands. It is not, however, a mineral in the strict sense of the term
because a mineral, as denned by Dana, 1 must be inorganic, homoge-
neous, and have a definite chemical composition, all three of which
requirements coal lacks. Yet it might be questioned whether the
varying amount of impurity in the form of ash in the coal is not
somewhat analogous to the impurities which are present in some
minerals producing coloring effects and variation in other physical
properties, and also whether the chemical formulae for some of the
complex silicates, such as members of the amphibole group, do not
vary almost as much as those for some varieties of coal when ash and
moisture are eliminated.

Although not a mineral, coal is a rock, since the geologist regards as
rocks all natural, solid substances, organic or inorganic, which com-
pose the earth's crust. It is as much a rock as are sandstone and
limestone, and when one attempts to classify the different varieties
of coal he meets with the same difficulties experienced in classifying
other rocks, for the reason that Nature does not draw sharp lines
between varieties. It is just as difficult to decide in some cases
whether a certain coal is bituminous coal or anthracite as it is to
determine when a shale, high in lime, passes into a limestone, or when
an igneous rock by variation ceases to be a syenite and becomes a
diorite. As a result of this lack of definiteness in the delineation of
our varieties of coal, many attempts have been made in recent years
to devise some concise method of classifying coals so that all the
terms employed will have some definite meaning. These attempts
have met with some of the same difficulties encountered by the petro-
graphers who have attempted the quantitative classification of ig-
neous rocks. Some of the objections are that in many cases elaborate
chemical analyses are required, and in most cases the chemical and
physical properties and the field characteristics are not closely enough
related to make the classification readily applicable to all varieties
under all conditions.

1 A textbook of mineralogy, p. i.

4 THE PHYSICAL PROPERTIES OF COAL

Physical Properties

In the description of the varieties of coal certain common physical
and chemical terms much used in mineralogy are employed. The
physical properties include specific gravity, hardness, fracture, color,
streak, luster, and physical constitution or texture. These are the
properties by which the public recognizes the different varieties of
coal in the trade, but the chemical composition is the determining
factor in the value of coal.

Specific gravity. The specific gravity of a body is the ratio of its
weight to the weight of an equal volume of water at 4 C. When the
average specific gravity of a quantity of coal is known the space which
a ton will occupy can be roughly determined, it being always remem-
bered that the volume of a ton will vary with the size to which the
coal is broken. The gravity of the common varieties of coal varies
as follows: Lignite 0.5-1.30; Bituminous coal 1.15-1.5; Cannel
1.2-1.3; Anthracite 1.29-1.65.

There are various methods for determining the specific gravity of
coal. It may be determined approximately for compact fragments
by drying the specimen carefully, weighing it in air (weight = W),
and then in water (weight = Wi). Since the specimen loses in
weight an amount equal to the weight of the water displaced, i.e.,
the weight of its own volume of water, the specific gravity is found

from the following formula: G = . Fora more accurate

W Wi

determination of the solid substance with the pores omitted the
specimen should be boiled in water in order that the air may be ex-
pelled from the pores. On the other hand, if the specific gravity of
a given mass of coal with all pores included is desired the body should
be coated with a thin veneer of paraffin or varnish to exclude all
water from the pores.

Determination by use of pycnometer: Accurate laboratory deter-
minations may be made on powdered coal by using the pycnometer.
This is a glass vessel which when filled to a specified mark contains
a given weight of water at a certain temperature. The dry powder
is weighed in air (weight = W). The pycnometer is weighed full
of water (weight = Wi), and then emptied. The powder is then
placed in the vessel, all air is excluded, the water is brought to the

SPECIFIC GRAVITY 5

same level as before the coal was added and the vessel is weighed
(weight = W 2 ). The specific gravity is then obtained from the fol-

lowing formula G = w + Wi _ w;

The following methods for determining the specific gravity of coal
and coke are used in the fuel-testing laboratories of the United States
Bureau of Mines. 1 To determine the true specific gravity the pyc-
nometer is ordinarily employed and about 3.5 grams of the 6o-mesh
coal or coke is used as a sample. About 30 c.c. of distilled water is
employed in a 5o-c.c. pycnometer, and the water is thoroughly boiled
after the sample is placed in the bottle, for the purpose of excluding
all air. The boiling is done on a water-bath and to avoid loss of par-
ticles of the coal or coke a one-bulb, 6-inch drying tube is connected
with the pycnometer by means of a small piece of pure gum tubing.
This drying tube is then attached to an aspirator and suction is
applied while the water in the flask is gently boiled for three hours.
The tube is then detached, the flask removed from the bath, and
almost filled with water previously boiled and cooled. When cooled
to the temperature of the room at which original weighing was made,
the pycnometer is stoppered and weighed. The formula employed

is the same as that given above, G = _ .

Determination by Hogarth-flask: A special method is recommended
as being more convenient and accurate for routine determinations
than the pycnometer method. This consists in the
use of a Hogarth flask such as that used in deter-
mining the specific gravity of iron ores. (Fig. i.)
This flask has a capacity of 100 to 125 c.c. To
make the test a lo-gram sample of 6o-mesh coal
or coke is weighed and introduced into the weighed
flask together with sufficient distilled water to fill it
half full. The flask is placed on a small electric
hot plate inside a lo-inch vacuum desiccator and
the latter is evacuated by an aspirator or air pump. IG * It ? gar * f

r specific gravity flask.

The water in the flask is kept boiling and the air

is expelled in thirty minutes with a good air pump. The flask is

then removed from the desiccator and filled to the tubulure with

1 Stanton, F. M., and Fieldner, A. C., Tech. Paper 8, 1913.

6 THE PHYSICAL PROPERTIES OF COAL

distilled water which has recently been boiled and cooled. The
stopper is inserted after having been coated with a thin film of vaseline
to prevent leakage.

After the flask has cooled to about 25 C. in a water thermostat,
distilled water that has been cooled in the same thermostat is drawn
through the tubulure until the water level is slightly above the mark
on the capillary of the stopper. If the end of the tubulure be inserted
in a small beaker of water and a slight suction applied to the stopper
this operation may be performed without removing the flask from the
thermostat. The flask should be left in the thermostat until the
temperature is 25 C. The water level may be adjusted to the mark
in the capillary by drawing in a little water. When this is done the
flask is removed, wiped dry, and weighed. The true specific grav-
ity is then- found by the formula used in the previously described
test.

Hydrometer method: To determine the apparent specific gravity
an apparatus is used which consists of a brass hydrometer immersed
in a galvanized-iron cylinder filled with water to a water-line. There
are two pans on the top of the hydrometer, the upper one being used
for weights and the lower for the sample of coal or coke. Below the
copper air buoy there is a brass cage highly perforated so as to allow
the air to escape during immersion. This cage carries the sample
when it is weighed under water.

To determine the specific gravity with this apparatus, brass weights
are placed on the upper pan causing the hydrometer to sink to a mark
on the stem between the pan and the buoy. This weight is desig-
nated by (W). The weights are removed and about 500 grams of
the sample in ij to 2 inch cubical lumps is placed in the copper dish.
Weights are again added until the instrument sinks to the same
mark on the stem as it did previously, (weight = Wi). The sample
is then transferred to the perforated cage and weights are added until
the same mark on the stem again touches the surface of the water;
(weight = W 2 ). We now have the following, (W Wi) = weight
of sample in air, and (W W 2 ) = weight of sample in water. Since
the body loses in weight when weighed in water an amount equal to
the weight of the water displaced the apparent specific gravity =
W - Wt

(w - wo - (w - w 2 y

SPECIFIC GRAVITY 7

Further, in determining the specific gravity of coke 100 X
apparent specific gravity = ntage by volume of coke subs tance,

true specific gravity

and 100 percentage by volume of coke substance = percentage
by volume of cell space.

Certain precautions are observed in making apparent specific
gravity tests on coke. It should preferably be in lumps of nearly
the same size and shape, and when the sample is immersed the hy-
drometer should be moved rapidly up and down a few times to remove
air bubbles. Coke samples, because of their marked porosity, should
not remain in the water more than five minutes and all specimens of
coal or coke should be thoroughly dried before tests are made.

Use of heavy solutions in determination of specific gravity: In an
investigation of the Canadian coals Porter and Durley 1 used a heavy
solution consisting of calcium chloride and calcium nitrate mixed so
as to obtain required densities. The crushed coal was placed in this
solution and separated, the heavier sinking, the lighter rising to the
top, and that of the same gravity as the solution floating suspended
in the liquid.

Gravity of "ash-free" and "moisture-free" specimens: In case it
is desired to obtain the specific gravity of the pure fuel with moisture
and ash excluded a correction must be made for these. The actual
specific gravity of the ash may be obtained, or, as Pollard 2 suggests,
the correction for ash may be made with a sufficient degree of accuracy
for all practical purposes by deducting o.oi from the specific gravity
of the coal for each per cent ash.

As a rule, high-carbon coals have higher specific gravities than
those low in carbon because of their more compact character. It
might be expected that the percentage of ash would be the factor
controlling the specific gravity of the coal in all cases since the mineral
matter entering the ash has, as a rule, a higher specific gravity than
the materials forming the combustible portion of the fuel, and this is
generally true if the proportions of the other constituents remain

1 Porter, J. B., and Durley, R. J., An investigation of the coals of Canada. Canada
Dept. of Mines, Vol. i, pp. 194 and 199, 1912.

2 Strahan, A., and Pollard, W., The Coals of South Wales with special reference to the
origin and distribution of anthracite. Memoirs of the Geol. Survey of England and
Wales, 2d ed., p. 12, 1915.

8 THE PHYSICAL PROPERTIES OF COAL

constant. It is found, however, from a study of a large number of
analyses that there is no regular ratio between the percentage of ash
and the specific gravity, and this seems to be due to a variation in
the volatile constituents, and the compactness of the fuel. It de-
pends also upon the nature of the ash since the presence of iron com-
pounds tends to raise the specific gravity above that for silica, alumina
and many other constituents.

That the specific gravity has a direct bearing on the burning qual-
ities of the coal is seen in the statement of Porter and Durley, 1 who
conclude as a result of their investigation of Canadian coals that few,
if any, coals which have a specific gravity over 1.6 are worth burn-
ing and that, excepting the anthracites and perhaps one or two special
types of coals, the approximate limit for commercially profitable
coals is 1.55. They add further that the pure bituminous coals of
Canada have a specific gravity between 1.265 an d I -3 2 5-

Hardness. The hardness of coal varies from that of the soft
lignites to that of the hard anthracites. It is difficult to state any
definite hardness for the coals other than anthracite because they
vary so much in different portions of the same fragment. Anthracite
varies from 2 to 2.5 in Moh's scale of hardness, which means that it
can be scratched with difficulty by the finger nail.

Fracture. The fracture in coal is a very important determining
factor in recognizing the ordinary types in hand specimens. The
anthracites break with a conchoidal fracture, i.e. the fracture leaves
a concave surface like that of a shell. This is characteristic also of
cannel coal, but the other varieties of bituminous coal generally break
with a rectangular or cubical fracture. The lignites fracture so that,
as a rule, they break into roughly tabular or flat, elongated fragments.
(Plates III and IV.)

In coal beds there are usually two sets of joints resulting from the
drying out of the rocks and the movement of the strata and these
run approximately normal to each other. Those which lie normal to
the strike and cut across the bedding of the coal are frequently known
as cleats. They are, as a rule, more clearly marked than the joints
running in the other direction.

Color and streak. The color of coal varies from light to dark
brown in the lignites to grayish black and jet black in the higher

1 Op. cit., p. 194.

PHYSICAL CONSTITUTION 9

grades. The streak is the color of the powder and it is determined
by making a mark on a piece of unglazed porcelain. For the coals
below bituminous it is brown to yellow. In bituminous coal it is
brownish to black and in cannel it is brown to black. The streak of
the higher-rank coals is black.

Luster. The luster, or the manner in which the coal reflects
light from its surface, is, like the fracture, often an important diag-
nostic property in a hand specimen. The anthracites have usually
a bright to almost submetallic luster and the luster of natural coke is
bright to submetallic, while that of cannel coal is usually, and that of
mineral charcoal, always, dull to earthy. Slaty coal is dull. In bi-
tuminous coal there are interlayered bright and dull bands, the former
representing portions of the coal formed from trunks or branches of
trees, and the latter portions being made up of mineral charcoal
and the smaller particles of vegetal matter or sometimes of impure
earthy layers.

Physical constitution. That coal has been derived almost en-
tirely from vegetal matter is proven by the presence in lignite of
abundant remains of plants and by the presence in decreasing amounts
of distinctly recognizable plant remains in all the varieties of coal
from lignite to anthracite. While some anthracite may not show a
trace of woody tissue to the naked eye, or even under the microscope,
some other portions of this coal from the same seam may show dis-
tinct evidence of the presence of vegetal constituents now altered to
coal. The microscope has been of great service in recent years in
aiding us in detecting the presence of altered vegetal remains in coals
where they were not formerly recognized by the naked eye. The
effects of the different kinds of vegetation or the different portions of
the same types of vegetation which enter into the coal may now be
recognized through the varying appearances of the coal produced
from these different materials. It is found that the spores from the
Cryptogamic plants which can be recognized under the microscope,
if comparatively free from other materials will produce the dull-
lustered cannel bands, the stems of trees usually produce bright
bands in the coal, while resins generally produce light-colored spots
or streaks. It has been found, therefore, that coal is usually made
up of the following constituents: (a) distinctly woody or xyloid
material, so abundant in lignite and to which Thiessen has given

PLATE I.

FIG. i. Photomicrograph of coal from No. 6 seam, Royalton, 111. (x 160).
Distinct woody tissue and a few flattened spores are visible. (After R.
Thiessen.)

FIG. 2. Same as Fig. i. Shows little xyloid tissue but many flattened
spores as white lines. / Io )

DEVELOPMENT OF THE MICROSCOPIC STUDY II

the name anthraxylon, from the Greek anthrax, coal and xylon, wood.
(b) canneloid, consisting chiefly of spores and forming the bulk of
cannel coal; (c) resins found in all coals but especially evident in
lignite and scarce in cannel; (d) de"bris, or the macerated material
mixed with the woody matter and derived from a great variety of
substances by the breaking up of stems, cells, cuticles, spores, and
particles of resin; (e) the " fundamental matter," 1 or the colloidal
groundmass in which the other constituents of the coal are embedded
and which is made up chiefly of the remains of the more readily de-
composable parts of the vegetal matter. It seems to consist chiefly
of fragments of cellulosic material, cuticles, cutinized cell walls, spore-
exines, pollen-exines, fragments of wood fiber, bits of resin, and all
the other finer particles of the material entering into the composition
of the coal. Some authors consider that large quantities of algal
remains are included in this substance and this subject will be dis-
cussed more fully in the chapter on the origin of coal

The Microscopic Study of Coal

Development of the microscopic study. The subject of the
physical constitution of coal has received a great deal of attention
during the last century and a half, and the historic development of
this study is well treated in the work by White and Thiessen. As
early as 1778 Franz von Beroldingen 2 outlined a logical theory for
the development of the coal swamps and for the origin of petroleum.
In 1833 H. Witham 3 made what was probably the first microscopic
examination of coal and his work was followed by that of Hutton. 4
In 1838 Link 5 boiled coal fragments in kerosene to render them more
nearly transparent for microscopic study. In 1855 Franz Schulze 6

1 White, D., and Thiessen, R., The origin of coal. U. S. Bur. of Mines, Bull. 38, p.
227, 1913.

2 Von Beroldingen, Franz, Beobachtungen, Zweifel, und Fragen, die Mineralogie
iiberhaupt, und insbesondere ein natiirliches Mineral System betreffend, vol. i, ist ed.,
1778, 2d ed., 1792.

3 Witham, Henry, On the internal structure of fossil vegetables found in the carbon-
iferous and oolitic deposits of Great Britain, 1833.

4 Hutton, W., Observations on coal. London and Edinburgh Phil. Mag. and Jour,
of Science, vol. 2, p. 302, 1833.

5 Link, Frederick, Uber den Ursprung der Steinkohlen und Braunkohlen nach mikro-
skopischen untersuchungen. Abhandl. k. Preuss. Akad. Wiss. Berlin, pp. 33-34, 1838.

6 Schulze, Franz, Uber das Vorkommenwohlerhaltenes Cellulose in Braunkohle und
Steinkohle; Ber. k. Akad. Wiss. Berlin, pp. 676-678, 1855.

12 THE PHYSICAL PROPERTIES OF COAL

adopted the maceration process for lignite and bituminous coal.
He digested the material in a mixture of dilute nitric acid and potas-
sium chlorate and then washed it in ammonium hydroxide and hot
alcohol, thus isolating woody fibers.

FIG. 2. Photomicrograph of bituminous coal showing bright bands due to
woody material and dark bands due to debris. (Photo by Thiessen.)

The work of these investigators was followed by that of J. W.
Dawson, C. W. von Giimbel, C. E. Bertrand, B. Renault, H. Potonie,
O. Barsch, D. White, and E. C. Jeffrey, all of whom have paid par-
ticular attention to the microscopic characters of coal. It was not,
however, until about 1910 that a satisfactory method was found for
preparing thin sections for study. This was discovered by Jeffrey
and described in his article published in that year. 1

Preparation of thin sections. In the preparation of thin sections
with the microtome there are two chief operations necessary, one the
removal of the mineral matter and the other the softening of the coal

1 Jeffrey, E. C., The nature of some supposed algal coals. Proc. Am. Acad. of Arts
and Sci., vol. 46, pp. 273-290, 1910.

PREPARATION OF THIN SECTIONS 13

so that it may be cut on the microtome like an ordinary botanical
or zoological section. The chief agent used for the removal of the
mineral matter, which consists mainly of silica, pyrite and carbon-
ates 3 is hydrofluoric acid and the softening agent is potassium or
sodium hydroxide. Jeffrey has recently concluded, however, that
phenol is a still better softening agent since it does not cause so much
swelling of the coal. 1 As to whether the hydroxide should have water
or alcohol added to it or be employed hot or cold depends upon the
resistance of the coal Thiessen 2 points out that alcohol, by causing
shrinkage, has the advantage of counteracting the expanding influence
of the hydroxide but it causes a more violent reaction. For cannel
Jeffrey 3 used a mixture of yo-per cent alcohol saturated with sodium
or potassium hydroxide. He allowed the coal to stand in this for
a week or more at a temperature of 60 to 70 C. until it was softened.
The mixture was then carefully removed by hot alcohol and the frag-
ments later treated with hydrofluoric acid for two or three weeks.
After this treatment the acid was washed out very thoroughly so
that no trace of it might attack the knife, the coal was embedded in
celloidin to stiffen it, and was then cut on a microtome. The celloidin
recommended is that known as Schering's. For those coals which
are more resistant to the softening process he uses either aqua regia
(HNO 3 + 3 HC1) or nitric and hydrofluoric acid of full strength.
He found that the acid treatment in many cases must be followed
by a treatment with sodium or potassium hydroxide after the acid
is removed. After the sections are cut they are dehydrated in a
mixture of absolute alcohol and chloroform. One difficulty was
experienced in preparing the sections for cutting; this was the fact
that hot alcohol and ether must be used in embedding the specimens
in the celloidin and these solvents dissolve some portions of the lower
grades of coal.

After various experiments Thiessen recommends that mineral
acids such as nitric acid, be avoided if possible, owing to their oxidiz-
ing action on the coal. In place of nitric acid alternate applications
of hydrofluoric acid and potassium or sodium hydroxide may be used
to soften resistant samples. In treating the samples with hydro-

1 Jeffrey, E. C., Methods of studying coal. Conspectus, Vol. 6, No. 3, 1916.

2 .Thiessen, R., Op. cit., p. 207

3 Jeffrey, E. C., Op. cit.

THE PHYSICAL PROPERTIES OF COAL

fluoric acid they should be placed in paraffin, ceresin, or rubber bottles
rather than in lead. For lignite a good solution is one part commer-
cial hydrofluoric acid and one part of 30 to 50 per cent alcohol In
which the blocks, which have been cut about 2 to 4 millimeters square
and 10 millimeters long, are placed until the mineral matter is dis-
solved. The acid may then be removed by potassium hydroxide
or sodium hydroxide and the section cut on the microtome without

further softening.

If the specimens are
resistant and need sof-
tening a 5 per cent solu-
tion of sodium hydroxide
in 50 per cent alcohol is
used. If they are friable
they may be embedded
in paraffin but this must
not be allowed to actually
penetrate the coal. The
sections may be bleached
in nitric acid or Javel
water. After dehydra-
tion they may be mounted
on slides with Canada
balsam.

Thiessen has, in his
more recent work, abandoned the use of the microtome and
adopted the grinding method since this has one distinct advantage
over the slicing method. 1 By preparing the specimens in this way
no part of the coal or its included foreign matter is removed by
the acids or other reagents and all the features of the coal may
be studied. It has a disadvantage, however, in that several
sections cannot be cut from the same specimen of coal almost as
easily as one. When the coal is once softened it is an easy task to
cut on the microtome many sections from the same block, for the
study of the internal structure of bodies occurring in the coal. The
sections of anthracite or bituminous coal must be ground extremely

1 White D., and Thiessen R., The origin of coal. Bull. 38, U. S. Bur. Mines. Also
Thiessen R., Structure in paleozoic bituminous coals. Bull. 117, 1920.

FIG. 3. Baxton megaspores from coal, with
air sacks and showing tri-radiate lines (x 25).
(After R. Thiessen.)

PREPARATION OF THIN SECTIONS 15

thin to permit any light to pass through them and it is only after
considerable practice that this grinding process can be successfully
carried out.

In preparing the sections a block less than an inch in diameter is
cut from the coal. The preliminary grinding is done with a paste
of carborundum powder on a fine textured carborundum lap, then
on the lap without any powder but with a stream of water playing on
the lap. The specimen is then rubbed on a hone with a stream of
water running over it until it is perfectly smooth and flat on the
polished side. After this operation the specimen is waterproofed
to prevent water entering the coal and causing it to swell. This
process consists of soaking the polished surface, first heated to about
105 C., in paraffin heated to the same temperature. This requires
only a few minutes.

After waterproofing, the specimen is cemented to a slide with a
strong, transparent cement consisting of 3 parts of Canada balsam to
2 parts of marine glue which have been heated together in a drying
oven at a temperature of about 105 C. for a sufficiently long time to
make a quickly setting, strong, but not brittle cement. This cement
is warmed until it is completely liquid and the specimen, wiped free
of any excess paraffin, is placed in it and pressed down in such a way
as to exclude all air bubbles.

The grinding of the section is continued by first grinding the speci-
men down as far as possible in the same manner as the first grinding
was done and then finishing it on the hone. Considerable care must
be exercised in doing the fine grinding, especially when the section
becomes very thin, to avoid breaking it up, and frequent exami-
nations should be made with the microscope to test its condition.
All powder must be removed from the specimen by washing before
it is rubbed on the hone. If the section is to be studied in oblique
illumination the dry specimen should be polished on a dry hone by
drawing it over the hone in one direction only.

By means of thin sections prepared as described above photo-
micrographs may be made with a magnification of 2000 diameters.
A detailed study can be made of the internal structure of the coal and
such a study throws a great deal of light on the composition and
origin of coals. Thiessen has made use of this in a very practical
way in the study of the occurrence of sulphur in coal and in the cor-

PLATE II.

FIG. i. Photomicrograph of horizontal section of coal from the
Pittsburgh seam showing numerous spores (x 800). (Photo by R.
Thiessen.)

FIG. 2. Photomicrograph of a section from the coal in the Black
Creek seam (x 800). It shows flattened spores peculiar to this seam.
(Photo by R. Thiessen.)

(16)

PREPARATION OF THIN SECTIONS 17

relation of coal seams. It has been found that most coal seams carry
certain plant spores which are characteristic of those seams and
which distinguish them from other seams, just as animal fossils dis-
tinguish one formation from another in a sedimentary series (Plate II).
While certain spores may be common to several seams there are
usually one or more types found only in one seam. The microscope
has also been of the greatest service in determining the origin and
character of boghead coals and oil shales.

CHAPTER II
THE CHEMICAL PROPERTIES OF COAL

Introduction

The chemistry of coal and its derivatives is a subject of extreme
complexity and of very comprehensive range. It cannot be treated
fully in a text of this sort but the main principles of the subject are
here set forth.

Since coal has been derived chiefly from woody constituents it
consists mainly of the elements which go to compose wood, but it
differs from wood in composition inasmuch as certain proportions
of those elements have been changed during the fermentation and
metamorphic processes which have altered the wood to coal. There
have been additions to the woody matter during the growth of the
vegetation, through streams and winds carrying particles of mineral
matter into the coal swamps. Again, after the woody matter has
changed to peat and even to the higher grades of coal, percolating
meteoric waters or hot magmatic waters, the latter rising in regions
where igneous rocks occur, may add a quota of their dissolved salts
to the coal and increase the ash and sulphur content. In some
regions of igneous activity a great variety of mineral compounds,
some comparatively rare, have been found in the coals. Besides the
vegetal and mineral matter a certain amount of animal matter may
have been imprisoned in the coal and this may have caused a variation
in some constituents, especially in the nitrogen and phosphorous
content. Fish remains have been found in the rocks associated with
coal seams in many localities, a notable example being that of the coal
basin at Commentry, central France. Fish remains have been
found also in some seams of cannel coal in England.

Constituents of Vegetation

Cellulose and lignocellulose. The chief constituent of vegetation
which goes to form coal is cellulose, the formula of which is (C 6 Hi O 6 ).
Many writers have discussed the derivation of coal from woody ma-
terials as if cellulose were practically the only important constituent

CELLULOSE AND LIGNOCELLULOSE 19

of the vegetal matter but Clarke 1 considers that wood consists more
nearly of equal proportions of cellulose and lignocellulose (Ci 2 Hi 8 O 9 ).
The latter is known also as lignone and lignin and its composition is
similar to that of jute fiber. From the formulae of these two com-
pounds their percentage composition is as follows:

Cellulose Lignocellulose

C 44 . 44 per cent C 47 . 06 per cent

H 6.18 " H 5.89

O49-38 O 47-05

If the composition of these substances be compared with that of
wood it is seen that the wood runs higher in carbon, averages about

FIG. 4. Photomicrograph of section of bituminous coal from No.
5 seam, Vandalia, Indiana (x 160). Consists chiefly of particles of
resin. (Photo by R. Thiessen.)

the same in hydrogen, and is considerably lower in oxygen. A fair
average composition for wood is C; 49.50, H; 6.25, and O; 44.00 per
cent. It will vary somewhat with the inclusion or exclusion of the
oils, waxes, and gums because they are much higher in carbon and
hydrogen and lower in oxygen than cellulose and lignocellulose.

1 Clarke, F. W., The data of geochemistry. U. S. Geol. Survey, Bull. 616, 3d ed.,
p. 739, 1916.

20 THE CHEMICAL PROPERTIES OF COAL

Resins, fats and oils. According to Thiessen 1 the coniferous
resins, resinoles, or resinolic acids contain C; 76.8 to 83.63, H; 9.7 to
12.9, and 0; o.o to ii.n per cent. The waxes contain C; 80.32 to
81.6, H; 13.07 to 14.1 and O; 4.5 to 6.61 per cent. The fats and oils
are composed of C; 74 to 78, H; 10.26 to 13.36, and O; 9.43 to 15.71
per cent.

Salts of organic acids. There have also been found in lignites
salts of organic acids such as whewellite, calcium oxalate, hum-
bold tine, ferrous oxalate, and mellite, the latter a salt of aluminum
and mellitic acid. Clarke 2 considers that since oxalic acid is readily
formed from cellulose, and calcium oxalate *is insoluble it is remark-
able that the oxalate is not more common in coal.

Humus acids. Humic acid occurs abundantly in peat and to a
considerable extent in lignite. The analyses of Borntrager 3 show
that in the black humus varieties of some German peats there are
12.50 to 30.00 per cent of humus acids to about 50 per cent of fiber.
In the brown coal at Falkenau, Bohemia, Von John 4 has found native
humic acid as a black crumbling coaly mass. It is soluble in ammonia
and sodium carbonate, and hydrochloric acid precipitates all ot the
organic material from solution. The percentage composition is
C, 54.98; H, 4.64; O, 39.98; and ash, 0.40; dried at 100. The
calculated formula is C 46 H46O25 and it resembles somewhat a sub-
stance found in the brown coal of Bavaria. The " paper coals"
of Russia also contain humic acid in considerable quantity.

The paraffin series. The presence of at least one of the lower
gaseous members of the paraffin series in coal has long been recog-
nized because methane (CH 4 ) or marsh gas is a well-known gas in
mines. Chamberlin 5 has also found ethane (C 2 H 6 ) to be present in
much smaller quantities. It is found in pulverizing the coal. The
presence of some of the higher members of the series as liquids and
solids has been pointed out by Thiessen who mentions the compounds
(CnHae), (C 2 4H 5 o), and (C 2 6H 54 ) discovered by Krafft in brown coal.

1 White, D., and Thiessen, R., The origin of coal. U. S. Geol. Survey, Bull. 38, p..

293, 1913-

2 Op. cit., p. 741.

3 Quoted by Clarke, Op. cit., p. 744.

4 Von John, C., Verhandl. K. k. Reichsanstalt, p. 64, Feb. 3, 1891.

6 Chamberlin, R. T., Notes on explosive mine gases and dusts. U. S. Bur. of Mines,
Bull. 26, 1911.

THE PARAFFIN SERIES 21

Paraffins with formulae (Ci H 2 2) and (C 32 H G 6) have been described
by Cohen and Finn 1 as occurring in the roof of a Yorkshire coal seam.
Hall 2 separated the oils (CiiH 24 ) and (Ci 3 H 28 ) from material taken
from the roof of a coal seam in North Staffordshire, and Bedson 3
found paraffins in the Whitehaven Collieries, whose formulae were
believed to vary from (Ci 3 H 28 ) to (CisH 38 ). It is probable that
members of the paraffin series are. much more common in coal than
they were formerly believed to be but they are likely to be over-
looked and not separated in analyses. Jones and Wheeler 4 have
found solid paraffins apparently existing free in several British coals
by treating the extract obtained by the solvent action of pyridine
and chloroform with pentane. This solution yields crystals of paraf-
fin wax melting between 55 and 59 C. and similar in composition
to those obtained by the destructive distillation of the coal. The
wax forms about o.io per cent of the total weight of the coals exam-
ined but it may not be present in all coals. It is the opinion of these
writers that the paraffins exist as alkyl or paraffinoid groups attached
chemically to another non-alkyl group, R. H. The paraffin would
thus be in a so-called " bound" condition and would occur as a com-
ponent part of a molecule whose general formula would be repre-
sented by RH C n H 2n +i where n may have any value up to at least
32. When coal is decomposed thermally the "free" paraffins are
rapidly distilled from the " bound" molecules according to the fol-
lowing system:

R H.C n H 2n+ i - R + C n H 2n + 2 or
R H.C R H 2n +i > R ~h C n H 2n + 2 H- C ni H 2ni

In somewhat the same way the formation of free naphthenes is ex-
plained.

1 Cohen, J. B., and Finn, C. P., Paraffin from Yorkshire coal seams. Jour. Soc. Chem.
Ind., Vol. 31, p. 12, 1915.

2 Hall, A. A., Oil from the roof of the Cockshead coal seam, North Staffordshire.
Jour. Soc. Chem. Ind., Vol. 26, p. 1223, 1907.

3 Bedson, P. P., Paraffin wax from the Ladysmith Pit. Jour. Soc. Chem. Ind., Vol.
26, p. 1224, 1907.

4 Jones, D. T., and Wheeler, R. V., The composition of coal. Trans. Chem. Soc.,
Vol. 105, p. 140, 1914.

22 THE CHEMICAL PROPERTIES OF COAL

Gases in Coal

Gases given off at normal temperatures. In many coal mines
methane, CH 4 , (marsh gas or, when mixed with air, fire damp) and
carbon dioxide, CO 2 , (choke damp or black damp) are found in large
quantities. Carbon monoxide, CO, (white damp) occurs in lesser
amounts than the other two but it is present in small proportions
in many mines. The quantity of gas, consisting chiefly of carbon
dioxide and methane, which escapes from some mines is very great,
running into many thousands of cubic feet. What is regarded as
the most gaseous mine in the anthracite region of Pennsylvania has
emitted as high as 2400 cubic feet of methane per minute.

Experiments have shown that coals will absorb gases in much the
same way as charcoal but regarding the actual condition of the gas
in the coal before mining there is still much uncertainty. Some
investigators have considered it as occluded but as Porter and Ovitz 1
have pointed out it is doubtful whether the gas exists as occluded gas,
or in a condensed condition, in the true sense of the term occluded.
The experiments of Chamberlin 2 and others have shown that the coal
gives up a considerable quantity of methane and some ethane when
pulverized but only a small percentage of that given off if the coal be
allowed to stand at atmospheric temperature for several months in
vacuo in a closed vessel. Porter and Ovitz have shown that although
the escape of methane from a mine seems to be dependent to some
extent upon the atmospheric pressure, the gas from broken coal after
a time escapes at approximately the same rate under atmospheric
pressure as in vacuo. The proportion of oxygen in the gas surround-
ing the coal does, however, have a great influence on the rate and
amount of the methane given off without causing a marked effect
upon the proportion of carbon dioxide set free.

From a practical standpoint these conclusions are important
because ventilating a mine carries off the gas set free but it also fur-
nishes more oxygen to the coal and thus facilitates the escape of

1 Porter, H. C., and Ovitz, F. K., The escape of gas from coal. U. S. Bur. of Mines,
Tech. Paper 2, 191 1. Also Parr S. W., and Barker, P., The occluded gases in coal. Uni-
versity of 111., Bull. No. 20, Vol. VI, 1909.

2 Chamberlin, R. T., Notes on explosive mine gases and dusts with special reference
to the explosions in the Monongala, Darr and Naomi coal mines. U. S. Geol. Survey,
Bull. 383, 1909.

GASES EVOLVED FROM COAL 23

deleterious gases. The amount of gas, both methane and carbon
dioxide, given off from coal which has been mined varies greatly with
different coals, but in practically all cases the proportion given off
during the first few days is much greater than that which escapes with
an increase in the length of time during which the experiment is con-
tinued. The loss of gas is usually complete in from three to eighteen
months and the deterioration in heating value is small. When coal
absorbs methane it gives up nitrogen somewhat less in amount than
the volume of methane absorbed 1 .

Gases evolved from coal heated below temperature of decom-
position. In addition to the gases given off in the coal seams at
atmospheric temperature and pressure considerable quantities are
driven out of the coal by heating it to a point a little below the tem-
perature at which decomposition begins. In view of the effect of
the absorption of oxygen on the gases given off it seems probable that
the increase of temperature not only expels the gas because of increas-
ing the volume but that it aids chemical action to a slight degree.
In peat the gases given off seem to consist chiefly of nitrogen and
marsh gas with smaller amounts of carbon dioxide. The presence of
the nitrogen is probably largely the result of air being imprisoned in
the fuel. The oxygen of the air is taken up by carbon or hydrogen
during the chemical processes accompanying the decay of the vegeta-
tion, leaving the nitrogen free in the peat.

The gases from lignite, heated to 100 C. in vacuo, consist, so far
as they have been tested, chiefly of carbon dioxide with small amounts
of carbon monoxide, nitrogen, oxygen, olefmes, and marsh gas. From
cannel coals the gases are largely methane and carbon dioxide. In
a series of analyses of English and Scotch cannels Thomas 2 shows that
when they are heated to 100 C. in vacuo they give from 16.8 to
421.3 c.c. of gas per 100 grams of coal and the composition of the gas
varies as follows:

CO2 6 . 44-84 . 55 per cent.

CH4 77 . 19-80. 69 per cent. Absent in three samples

C2He 2 . 67-7 . 80 per cent. Absent in two samples

C 3 H 8 0.91 percent. Present in one sample only

C4Hio Not present

N 2 5 . 96-46 . 06 per cent.

1 Katz, S. H., Absorption of methane and other gases by coal. U. S. Bur. of Mines,
Tech. Paper 147, 1917. Also McConnell, W., Gases enclosed in coal and coal dust.
Jour. Soc. Chem. Ind., Vol. 13, p. 25, 1894.

2 Thomas, J. W., Jour. Chem. Soc., Vol. 30, p. 144, 1876.

THE CHEMICAL PROPERTIES OF COAL

A sample of Whitby jet yielded 30.2 c.c. of gas consisting of CO 2 ,
10.93; C 4 Hio, 86.90; and N 2 , 21.7 per cent. From these analyses
it is seen that carbon dioxide is present in all, and abundant in some
coals. Nitrogen is present in fairly large proportion in all these
coals and is present also in jet. While these results obtained by
Thomas are interesting it may be questioned whether they can be
fully relied upon in view of the difficulty experienced at the present
day with more modern analytical methods, in our attempts to rec-
ognize certain of these rarer gases.

The gases obtained from bituminous coal and anthracite under
the conditions stated above are very variable in amount and com-
position. Von Meyer 1 found ethane up to 23 per cent and other
undetermined hydrocarbon gases in small amounts in some Saxon
and Westphalian coals. From the works of W. McConnell 2 on the
coals from Newcastle and of Thomas 3 on the Welsh coals the following
figures were compiled:

Volumes of gases derived from 100 grams of bituminous coal heated
in vacuo at 100 C., 1.61 to 818 c.c.; from semibituminous and steam
coal, 73.6 to 375.4 c.c.; and from anthracite, 555.3 to 600.6 c.c. The
composition of the gases varied as follows:

Semibituminous and
steam coal

Bituminous

Anthracite

C0 2
CH 4 and other
paraffins
O 2

5 .04-1 8. 90 per cent

72.51-87.30
0.33 i .02

o . 7 2-36 . 42 per cent

o . 40-88 . 50
0.80 9 .41

2. 62-14. 72 per cent
84.18-93.13

N 2

3.49-14.62

8.70-80.11

1. 10- 4.25 '*

The paraffins in the bituminous coals consisted in some cases almost
entirely of methane although ethane was present in greater or lesser
amount. The steam coal of Seaton Delaval gave off no hydrocar-
bons, the gas consisting entirely of carbon dioxide, oxygen, and nitro-
gen.

The above figures go to show that in anthracite the predominant
gas is methane, while in the lower types of coal carbon dioxide, nitro-

1 Quoted by F. W. Clarke, Op. cit, p. 759.

2 Op. cit.

3 Thomas, J. W., Jour. Chem. Soc., Vol. 28, p. 793, 1876.

PRODUCTS OF DISTILLATION 25

gen and methane form the main constituents of the gas. This is
further illustrated by the fact that if heated to higher temperatures
but still below the point of decomposition the relative proportion of
methane increases while that of nitrogen decreases. The longer the
coal is heated the more gas is given off, this being especially true of
hard compact coals such as anthracites. The bulk of the gas, however,
is evolved early in the experiment.

Relation of mine gases to volatile constituents in coal. The
proportion of volatile matter in coal seems to have little or no relation
to the percentage of gas evolved on heating below the temperature
of decomposition and the explosibility of mine gases and dusts seems
to depend much more upon the nature of the gases evolved than upon
the relative percentage of volatile matter in the coal.

Analyses made by Thomas of the gases from blowers in coal seams
and of those gases obtained from the seam by boring show that there
is little difference between them. In some blowers the oxygen reaches
over 10 per cent and nitrogen over 41 per cent of the gas, but oxygen
is lacking in many. Carbon dioxide is less than i per cent in nearly
all, while marsh gas constitutes over 90 per cent of the gases derived
from practically all blowers and borings in the seams.

Products o Distillation

The chief products resulting from the distillation of coal are coke,
tar, light oils, water of decomposition, and a mixture of gases con-
sisting chiefly of NH 3 , H 2 S, H, C0 2 , CO, unsaturated hydrocarbons,
and C n H 2 n+2. The processes of distillation and the chemistry of
the resulting products are subjects which are so complex that a de-
tailed discussion of them involves a treatment of the subjects of gas
manufacture, the dye industry, and many other related problems.

(Fig. 5) 1 -

The relative proportions of the volatile constituents obtained
depend upon many factors, such as the kind of coal and the con-
ditions under which the coal is heated, including the temperature, the
pressure and the length of time involved. It has also been found that

1 For detailed descriptions of experiments and conclusions regarding the volatile
matter in coal, see Porter, H. C., and Ovitz, F. K.. The volatile matter of coal. U. S.
Bur. of Mines, Bull, i, 1910; and The primary volatile products of the carbonization of
coal. Tech. Paper 140, 1916. Also Rittman, W. F., and Whitaker, M. C., A bibliog-
raphy of the chemistry of gas manufacture. U. S. Bur. of Mines, Tech. Paper 120, 1915.

THE CHEMICAL PROPERTIES OF COAL

a wet coal will produce a greater ammonia yield and less gas, but a
gas richer in hydrocarbons, than a dry coal.

Effect of temperature on quantity and kind of constituents
evolved. The experiments of Porter and Ovitz have shown that,
as a rule, more than two-thirds of the organic substances are de-
composed at temperatures below 500 C. It is probable that some
change takes place in exposed coal at atmospheric temperatures but
appreciable quantities of volatile matter are given off from most
coals at 250 C. In a series of experiments on bituminous coals
Burgess and Wheeler 1 found that occluded or " condensed" gases
which are unextractable at atmospheric temperatures are extracted
in vacuo by heating from 150 to 200 C. These gases consist mainly
of the higher members of the paraffin hydrocarbons. The following
table shows the quantity of gas and its composition evolved from 100
grams of coal heated to 100 C. and the same amount heated to 200 C.

Temperature

Volume of gas

Composition per cent

C0 2

OH,

CH 2n(n72)

C.H 2n+2

100
200

34 c.c.
65.5 c.c.

6.70
8.85

1-65
0.70

0.85
0.85

1.30
2 .90

1.40
2.6o

1.90

2-75

84.55
Sl.OO

Of the gas obtained at 200 about 7.5 per cent consisted of butane.
The identification of this gas has, however, been called in question
by some chemists.

The younger coals of the western and middle-western states break
down more quickly, as a rule, than the Appalachian coals. This
greater ease of disintegration is probably related to the proportions
of resinous and cellulosic constituents, the older coals yielding a
larger proportion of hydrocarbon constituents from the resinous
materials and the less mature coals a greater proportion of carbon
dioxide and water. The early products of distillation are mostly
CO 2 , CO, and H 2 O and these come off slowly up to 450 C. At this
temperature the products of the lower grades of coal are mostly water
and carbon dioxide, and those from bituminous coal largely members

1 Burgess, M. J., and Wheeler, R. V., The distillation of coal in a vacuum; Trans.
Chem. Soc., Vol. 105.

EFFECT OF TEMPERATURE 27

of the paraffin series, with gases of the series C n H 2n +2, higher than
CH 4 , predominating below 400 C. Water of decomposition is ex-
pelled much more rapidly between 250 C. and 500 C. than at a
higher temperature.

Sulphurous gases, such as H 2 S, begin to be formed at 250 C. and
the production rises to a climax more rapidly than that of hydrogen
or the hydrocarbons. The thermal decomposition of the volatile
matter takes place very readily at temperatures above 750 C. and
the percentage of hydrogen and the hydrocarbons increases, with
hydrogen predominating, at the higher temperatures. The increase
of these gases takes place, however, at the expense of the tar, which
has been increased 13 per cent in yield from Pittsburgh coal by heat-
ing it below 500 C. rather than at the usual temperature employed
in carbonizing coal. It is evident that the composition of the tar
obtained at the different temperatures will vary considerably. At
900 C. the volatile matter is practically all expelled from a coal of
the Pittsburgh type although heated only a few seconds, which is
the time necessary to raise the temperature to that point.

The experiments of Burgess and Wheeler 1 in England produced
results for low temperature distillation gases, very similar to those
described above, but these authors concluded that there is a decompo-
sition point between 700 and 800 C. at which hydrogen is distilled
at a marked increase in rate. This change is considered as indicating
the presence in the coal of two types of compounds, one type decom-
posing at a lower temperature than the other and yielding mostly
hydrocarbons in contrast to the other which yields hydrogen as the
chief decomposition product. Although Porter and Ovitz found that
hydrogen was given off in greater proportions above 750 C. they do
not consider that any line of demarcation may be drawn near this
point which would indicate the decomposition of distinct compounds.

1 Burgess, M. J., and Wheeler, R. V., The volatile constituents of coal. Jour. Chem.
Soc., Vol. 97, p. 1917, 1910; Vol. 99, p. 649, 1911. Clark, A. H., and Wheeler, R. V.,
The volatile constituents of coal. Jour. Chem. Soc., Vol. 103, p. 1704, 1913.

THE CHEMICAL PROPERTIES OF COAL

By-product tests on coals:

TABLE SHOWING RESULTS OF BY-PRODUCT TESTS
ON VARIOUS COALS 1

Number of Samples

ii
(Air-dried)

Number of tests

averaged. . . .

Coke, per cent. . .

79-i

71-4

63.1

44-7

53-o

58.6

63.9

Tar, per cent ....

7.2

n-3

II-9

7-i

5-5

12.3

10.3

Water, per cent .

i-3

4-9

10.7

27-5

19.0

ii. 8

IO.O

Ammonia, pounds

of sulphate per

ton

12 Q

23 8

2C 2

27 ^

26 7

26 i

26 7

CO 2 , per cent. . . .

j
0.44

*o * w

0.72

o o
1.20

^ /

8.14

^.\J . j

8.41

*\> . ^
3-i3

' v }

2.13

H 2 S, per cent. . . .

O.O7

0.25

0.46

0.08

O.II

0.24

0.30

Gas, cu. ft. per

ton (a)

Q.7OO

8,140

8.4OO

7,8^0

8,170

7,620

7 Q4.O

Composition of

y / ***

^> AiJ.W

U,f.\SW

/ J^O

Uf ft y W

^ )\J 4\S

/ >:7T- W

gas (6) . . .

Illuminants

1.4

3-2

3-o

2 .2

2.6

5-7

5-5

3-2

S-i

7-4

!9-5

21.4

14-9

12.3

CH 4 , C 2 H 6 , etc. . .

26.4

27.8

26. 3 (C)

18.1

22.6(C)

27.2

25.4

67.8

6r.o

56.8(c)

^4 o

4Q. 2(^)

47.8

C2 I

I .2

2-9

6-5

OT- * ^
6.2

T^^'O \ /

4-i

4-4

oo
3-7

Value of "n" in

C n H 2n+2

(*)

1.27

(*)

1.18

()

1.32

1.29

Total volatile

products with-

out moisture. . .

19-7

27.4

29.8

33-3

35-5

38.5

32.4

Water of consti-

tution

O.I

3-7

3-6

5-5

7-5

8.9

6-3

Inert volatile

matter (d)

0.7

4-7

5-i

14.0

16.3

12.4

8.8

(a) Calculated to dry basis at o C. and 760 mm. pressure, free of air and
carbon dioxide. (6) Calculated to carbon dioxide and oxygen-free basis, (c)
Hydrogen not determined separately by palladium but calculated from com-
bustion: Methane probably high and hydrogen low. (d) Sum of carbon dioxide,
ammonia and water of constitution.

The coals used in these tests were as follows: No. 16, Pocahontas;
No. 3, Connellsville; No. 23, Harrisburg, 111.; No. n, Sheridan,
Wyoming subbituminous coal; No. 25, Utah bituminous coal; No.
46, Wyoming bituminous coal.

Burgess and Wheeler 2 distilled anthracite at 900 C. for varying

1 Porter and Ovitz, U. S. Bur. of Mines, Bull. I, p. 26, 1910. See also Church, S. R.,
Methods for testing coal tar and refined tars, oils, and pitches derived therefrom. Jour.
Ind. and Eng. Chem., Vol. 3 p., 227, 1911.

2 Burgess, M. J., and Wheeler, R. V., The volatile constituents of coal, Pt. II. Trans.
Chem. Soc., Vol. 99, pp. 665-6, 1910.

=1 .

.'GOIM

GAS LIQUOR |

ilSULFID BEN20 '- TOLUOL XYLOL

II SULFUR JI C YANOOEN|{
" " 'I

AMMONIUM AMMONIUM JJ AMMONIUM AMI^

_SULFATE II NITRATE Ij CARBONATE || CARP

I SULFOCYANIDE | | FERROCYANIDE

f FERRICYANIDE | | PRUSSIAN BLUE )

LIGHT OIL

MIDDLE OIL

I C ""jr" ||. U T,,LO,U,| |

| PAINT THINNERS | [ *",

| PHENOL | CRE80L | I BA . . [. ,,. |

P"H T E

^NO'L' 1

h'REslNS-||^S-S- || j*W |

L^^'N||8AL,C^?C\CI D llk^

1 DYE STJFF8 | | FLAVORINGS I

1 PMENACETIN | Lg

fffr. |P

PICRIC I

DYE STUFFS

1 I

XPLOSIVES ^

HEA

I CRUDE

NAPHTHALIN |

8Hi NGL E I I NA R P E H F THALIN I | PHENOL ||cRESOL|[

PXTHALICAC1D j NAPHTHOU8

{ NAPHTHOU8 |

EZTJ__

SDLE

INDIGO

1AMIDO NAPHTHOL I Pi
8ULFOACID 1 1

| PHENOL ~\ j CRE80L8 [ I PORE TOLUOL

LOY^^Fr, j| SOLVENT | | "JTROin^

I EXPLOSIVES I j TOLUIDir

II "gffl I L_

I HMOJ I | PMOTOaRAPMY"^ | DYE 8TUFM || ANTPYRIN

T6STI!)F.F I INDIGO

FIG. 5 Distillation products of coal and their commerci

>AL

| COKE

1 AMMONIUM. 1
_|| CHLORIDE |

1 1

! 1 -

_ | ELECTRODES || LAMP BLACK | | LUBRICANT j CRUCIBLES || ELECTRODES |

i'lL

REFINED TAR PITCH

j PRES^TION 1 * C1N | | LAMP .

LACK PAINTS TARRED FELT | P'PE SUB SIDEWALK PAVING
1 1 WITH p,TCH II COATING || FLOORING || COMPOSITION || M ATERIALS

F~l 1 iM^SoN I

I 1

.__ TAR-ROK 1 TARVIA 1

1 PRESERVATION 1 1 CEASES

ANTHRACIN |

.Kg | 1 ^ NTAN j |

| SHINGLES || ROOFING II HOOFING |l TION (PROOFING |

| CARBOZOL |j

PHENANTHRIN | | ANTHRACIN

JANTHRA-
1 QU.NONE 1

JLPHO U ACIS E QUINAZARIN

J ,

DYE STUFFS |

1 ALIZARIN
DYE STUFFS

1 1 ALGOL I
I 1 DYE STUFFS I

SOFT PITCH

, 1

, 1 1

INSULATION 1 p^J^L PAVING MEDIUM

| III

' ACID | | BENZOLDEHYDE

ITCH; 1

YE STUFFS | PERFUMES 11 BE A N C 2 ,' C |

BRIQUETS II coJ^J^g || EL C E A C R 7 N D 8 E8 || TARGETS 1 1 POWD. FUEL 1 1 PITCH

i ! " " ' T '

| METAL CASTING j | FUEL |

r L_

1 ""FUMES | .88m.

FOOD
1 PRESERVATIVE |

es. (Reproduced by permission

of the Barrett Company.)

HAT

L i ..;.-. i^ _

THE SOLUBILITY OF COAL AND ITS DESTRUCTION BY ACIDS 29

periods of time and recorded the results for periods of five seconds
each. During the first five seconds 6.65 c.c. of gas at o C. and 760
mm. were evolved, and during the tenth five-second period 20.95 c - c -
The composition of the gas taken at the periods mentioned was as
follows when calculated on a " nitrogen-free " basis:

A B

NH 3 6.10 0.20

C 6 H 6 3-80 o-35

H 2 S 2.75 0.35

CO 2 9.85 1.40

C 2 H 2 0.30 nil

C 2 H4 2.35 nil

CO 16.65 5-6o

H 2 31-20 82.30

CH4 25.95 8 -4o

C 2 H 6 1. 10 1.35

The tarry products derived from the distillation of coal are of great
industrial importance and their derivatives are obtained by numerous
chemical processes, some of which are of remarkable complexity. 1
The following plan shows the main products derived from coal and
it sets forth the relations among these various compounds. (Fig. 5.)

The Solubility of Coal and its Destruction by Acids

The degree of solubility of different coals varies greatly owing
to the fact that they are not homogeneous and their resinous con-
stituents will dissolve much more readily in some reagents than their
cellulosic constituents. Coals which contain much humic acid will
dissolve to a considerable extent in alkaline solutions, while the
cellulosic constituents may be attacked by nitric acid. Most of the
resinous constituents are soluble to some extent in organic solvents
such as benzine.

Peat and the xyloid lignites are partially soluble in caustic alkalies
and almost completely soluble in alkaline hypochlorites. The com-
pact lignites or subbituminous coals are readily attacked by the al-
kaline hypochlorites but are only slightly soluble in caustic alkalies,
while bituminous coals and anthracite are not dissolved by alkaline
solutions. Dilute nitric acid will attack lignite and strong acid will
slowly attack the higher coals but a mixture of nitric and sulphuric

1 Hoffman, A. W., Etudes sur les matieres colorantes derivees du goudron de houille
Compt. Rend., Vol. 55, pp. 781, 805, 817, 849 and 901, 1862, and Vol. 56, pp. 1033 and 1062.

THE CHEMICAL PROPERTIES OF COAL

acids will completely break down the more reshtant coals leaving a
deep brown solution from which the coloring matter is precipitated
on the addition of water. 1

By the action of nitric acid on finely pulverized coal Guignet 2 ob-
tained oxypicric acid and a mixture of oxide of iron and sulphuric
acid resulting from the pyrite in the coal. By boiling the mixture
in water with barium carbonate the oxide of iron and the oxalic and
sulphuric acids were thrown out while the oxypicrato of barium re-
mained. On precipitating the barium as sulphate, crystals of oxy-
picric acid remained. There were left on filtering the original nitric
acid solution compounds which were insoluble and which exploded
when heated.

Most of the resinous compounds in coal are partially soluble in
the strong acids, they are partially or entirely soluble m alcohol,
and most of them partially so in ether and in turpentine. The sol-
vent action of benzine is variable. It is thus evident that the pro-
portion of resinous constituents in coal will affect to a considerable
extent its solubility in various solvents.

Relation of solubility to coking qualities. The results of Vig-
non's 3 work show that there is some definite relation between the
composition of the coal, its solubility in various organic solvents and
incidentally its coking quality. The coals from the Loire region
showed the following results when treated with aniline. Taking
fat gas coals, semi-fat coals, and lean or dry coals he obtained the
following results:

Initial weight

Weight after
treatment with

Percentage

Percentage
soluble, ash

aniline

deducted

(i) Fat gas coal. . .
(2) Semi-fat coal. .

1.46-1.68
1.17-1.32

I .12-1 .29
I .09-1 .23

23.40
6.58

26.8
7.2

(3) Lean or dry

coal

2 . 172 .OI

2 . 142 .OI

1.56

1.8

1 Fremy, E., Recherches chimiques sur les combustibles mineraux. Compt. Rend.,
Vol. 52, pp. 114-117, 1861.

2 Guignet, E., Sur la constitution de la houille. Compt. Rend., Vol. 88, pp. 590-592,
1879-

3 Vignon, Leo, Sur les dissolvants de la houille. Compt. Rend. VoL 158, pp. 1421-
1424, 1914.

RELATION OF SOLUBILITY TO COKING QUALITIES

The portion of the coal which is soluble is richer in hydrogen than
the insoluble portion and from this it may be inferred that the coking
coals will differ from non-coking coals in their solvent action with
aniline.

On treating coal with alcohol, ether, benzine, toluene, aniline and
nitro-benzine, Vignon obtained the following results with 50 c.c.
of the solvent and 10 grams of coal.

Soluble at ordinary temperature for
24 hours

Soluble at boiling point for 3 hours

Alcohol

0.076 per cent

0.0167 per cent

Ether

0.059

Benzine ....

0.080 '

0.191

Toluene.

0.078

0.190 "

Aniline
Nitro-benzine

2.250
i .410

12.050
3-190

From this table it is evident that aniline js the most active solvent
for these bituminous coals of the Loire basin. Of the other common
solvents pyridine and phenol may be regarded as the most active.
Clark and Wheeler 1 claim that a coal may be divided into two types
of compounds recognized by their differential solvent action with
pyridine and chloroform, one of these compounds being higher in
hydrogen and the other in hydrocarbons.

Phenol has been employed as a solvent for coal by a number of
chemists, but the first extensive experiments to determine the deriva-
tives of the solution with phenol were carried out by Parr and Hadley 2
and by Frazer and Hoffman. 3 The latter authors found that 10.87
per cent of an Illinois non-coking, bituminous coal was dissolved in
phenol. From this solution a large number of derivatives were
extracted, some of which are believed to be pure compounds. Parr
and Hadley found that there is a distinct relation between the per-
centage of the coal dissolved in phenol and its coking qualities. The
coking constituents are almost all dissolved in this solvent and oxi-

4 Clark, A. H., and Wheeler, R. V., Op. cit.

2 Parr, S. W., and Hadley, H. F., The analysis of coal with phenol as a solvent, Uni-
versity of 111., Bull No. 10, Vol. XII.

3 Frazer, J. C. W., and Hoffman, E. J., The constituents of coal soluble in phenol.
U. S. Bur. of Mines, Tech. Paper 5, 1912.

32 THE CHEMICAL PROPERTIES OF COAL

dation of the coal greatly affects its relative solubility. This solvent
was also used to extract organic sulphur.

Chemical Causes of Spontaneous Combustion 1

There has been a great deal of speculation regarding the cause of
spontaneous combustion of coal and many have assigned it to the
oxidation of pyrite. It is now recognized, however, that while the
oxidation of pyrite and the action of the sulphuric acid on moisture
in the coal may produce some heat, the fundamental cause of the
heating is the oxidation of the coal itself. The sulphuric acid re-
sulting from the oxidation of pyrite is a powerful oxidizing agent and
its presence facilitates oxidation of the coal, but coal itself will oxidize
rather rapidly for a time after mining. If there is a good circulation
of air it will not take fire but if there is only a partial supply of air
oxidation goes on and the heat is retained. As the temperature of
the fuel rises the rate of oxidation is greatly accelerated and in con-
sequence there is cumulative action progressing towards the tempera-
ture of combustion which varies from about 300 C. upward depending
upon the character of the coal. According to Fayol finely powdered
lignite may ignite at a temperature as low as 150 C. and gas coal
at 200 C.

There is a fairly definite relation, as shown by Wheeler, 2 between
the temperature of ignition of coal dust and the proportion of its
resinous constituents, which are soluble in pyridine.

The oxidation process goes on in both moist and dry coals, although
moisture aids the process very greatly. If the coal be completely
covered with stagnant water oxidation almost ceases after a bref
time but circulating water may bring in new supplies of oxygen to le
coal. The finer the coal, the more rapid is the oxidation of a given
surface, other things being equal. The percentage of volatile matter

1 Parr, S. W., and Kressmann, F. W., The spontaneous combustion of coal. Univer-
sity of 111., Bull. 16, 1910.

Moissan, H., Traite de chimie minerale, Vol. 2, pp. 363-364, 1905, (on spontaneous
combustion).

Stansfield, E., An investigation of the coals o* Canada. Vol. 6, Dept. of Mines, Canada,
1912.

Hapke, L., The causes and prevention of spontaneous combustion. Chem. Zeit.
17, p. 916, 1893.

2 Wheeler, R. V., The volatile constituent? of coal, Pt. IV: The relative inflamma-
bilities of coal dusts. Trans. Chem. Soc., Vol. 103, p. 1715, 1913.

SULPHUR 33

seems to make little difference in the spontaneous heating as all
types of coal have been known to heat. 1 There are, however, no
authentic cases reported where anthracite has actually taken fire in
storage. The natural process of heating is often accelerated by the
proximity of the coal bins to furnaces and other sources of heat and
this, no doubt, explains why coal on shipboard and in other places
adjacent to boilers often takes fire while in the bins.

A certain amount of loss in the heating value of coal takes place
during weathering and the accompanying oxidation. This may be
readily understood when the results of White's investigations are
considered, since he found oxygen and ash to be of almost equal anti-
calorific value. 2 Further, the loss of methane accompanies the oxi-
dation process and the heating value of this gas amounts to a small
item.

Source of Mineral Constituents

The source of many of the constituents of coal is self-evident when
the composition of wood is considered. The carbon, hydrogen,
oxygen, and nitrogen may all be derived directly from the wood but
there are many other constituents whose source and whose condition
in the coal are not so readily recognized. In addition to the nitrogen
in wood, which varies from less than i per cent to over 3 per cent,
some is supplied by animal matter and it is probable that a little is
added to the coal from the air through its imprisonment in the vege-
tation before it becomes coal.

Sulphur. Sulphur is a constituent of considerable economic im-
portance in coal because it reduces the quality of coke for metallurgical
purposes, it increases corrosion of boilers and in quantities of more
than about 2 per cent it increases clinkering in furnaces by aiding
the fusion of ash. This 2-per cent limit will vary, however, with the
varying proportions of ash and sulphur present and it is probable
that the iron combined with the sulphur in pyrite may aid the fusi-
bility of the ash almost as much as the sulphur. In coking approxi-
mately one-half of the sulphur in the coal is supposed to enter the
coke. This proportion will apparently vary with the proportion of

1 Porter, H. C., and Ovitz, F. K., Deterioration and spontaneous heating of coal
in storage. U. S. Bur. of Mines, Tech. Paper 16, 1912.

2 White, D., The effect of oxygen in coal. U. S. Geol. Survey, Bull. 382, 1909.

34 THE CHEMICAL PROPERTIES OF COAL

organic and inorganic sulphur. While one molecule of the sulphur
in pyrite (FeS 2 ) may be removed in the burning process leaving the
other to enter the coke with the iron, this relation will not hold for
the proportions of organic sulphur, the compounds of which are not
so well known.

Sulphur occurs in varying amounts in coal, from less than i per
cent to 10 per cent or more. It commonly amounts to between one-
half of i per cent and 3 per cent although many of the coals of our
middle-west states carry between 3 and 5 per cent. The sulphur is
in two forms: organic and inorganic. The inorganic type is most
familiar and it occurs in the following forms: (i) Mineral sulphides,
(2) Sulphates and (3) Free sulphur.

Inorganic sulphur. Of the sulphides iron pyrite (FeS2, Isometric)
and marcasite (FeS 2 , Orthorhombic) are the most common. Chal-
copyrite (Cu'FeS 2 ), arsenopyrite (FeAsS), stibnite (Sb 2 S 3 ) and a few
other sulphides have been found but they are rare except in some
regions where volcanic activity has occurred. Pyrite or iron pyrites,
also known as " fools' gold" is responsible for most of the "sulphur
balls," "coal brasses," and "sulphur diamonds" found in coal seams
although marcasite frequently occurs in sulphur balls and is mis-
taken for pyrite since many people do not distinguish these two
minerals from each other. The sulphide occurs in largest quantities
in concretions, commonly known as "sulphur balls," in lenses or
bands running parallel with the coal seam or in veinlets cutting across
the seam. When in sufficiently large quantities it is separated from
the coal in mining and at some mines it is sold for the manufacture
of sulphuric acid. In addition to the masses of pyrite which are so
evident to the naked eye, Thiessen 1 has shown that in practically all
coals and also in peat there are numerous grains of pyrite averaging
25 to 40 microns in diameter, distributed through the fuel (Fig. 6).
These appear to be more abundant in the xyloid bands in the coal
and it seems quite probable that at least part of the pyrite has been
formed by combination of iron with hydrogen sulphide derived from
organic sulphur. These grains of sulphide are so small that they
cannot be removed from the coal by washing unless the coal has been
ground to fine powder.

1 Thiessen, R., Finely disseminated sulphur compounds in coal. Trans. Amer. Inst.
Min. Met. Eng. Vol. LXIII, p. 913, 1920.

ORGANIC SULPHUR

The most common sulphate known is calcium sulphate or gypsum
(CaSO4.2H 2 O). Sulphates of iron, copper and magnesium may also
occur but they are not abundant. These salts occur as a result of
the action of sulphuric acid on carbonates or by the oxidation of
sulphides. The sulphuric acid may result from the oxidation of
iron pyrite as in the following equation : FeS 2 + 76 + H 2 = FeSCX
+ H 2 S0 4 .

Native sulphur occurs only as the result of extreme oxidation of
some of the minerals mentioned above and it is rare.

FIG. 6. Photomicrograph showing finely disseminated pyrite in coal (x 155).
(Photo by R. Thiessen.)

Organic sulphur. It has for many years been recognized that a
portion of the sulphur in coal must exist in some form other than
the mineral sulphides and sulphates. This is shown by the fact that
in some coals the sulphur does not exist in such proportions that it
can be combined with the elements necessary to form these mineral
compounds. Sulphur which gives every indication of being com-

36 THE CHEMICAL PROPERTIES OF COAL

bined in organic compounds in coal has been found running from 0.5
to 2 per cent, and 3 per cent is reported in one coal. Thiessen points
out that there is sulphur in the proteins of practically all plants and
in addition to the protein sulphur there is some non-protein sulphur
in most of them. This organic sulphur by putrefaction is changed
to hydrogen sulphide (H 2 S) which can precipitate sulphides of the
metals from their soluble salts. The plants obtain the sulphur,
which they assimilate in the form of sulphates, from the weathering
of sulphides in the rocks or from the products of sulphur bacteria,
which oxidize hydrogen sulphide to sulphuric acid. The sulphuric
acid can then form calcium, magnesium or potassium sulphates,
which are assimilated by the plants. R. Dawson Hall has also called
attention to the fact that many coal seams contain a larger proportion
of sulphur than the rocks lying above and below them, indicating
the presence of organic sulphur compounds in coal. He early sus-
pected that some of the sulphur in pyrite had an organic origin.

Phosphorous. Like sulphur, phosphorous is an important con-
stituent in coal which is to be used in making coke since they both
enter the coke to at least some degree. Its presence in the coal may
be due to solutions formed by streams running over rocks which
contain calcium phosphate in some form and these solutions then
precipitating the phosphate in the swamps where the coal vegetation
was laid down. It is evident, however, that a certain percentage of
the phosphorous is derived directly from the vegetation which produces
the coal. In a study of the origin and distribution of phosphorous
in bituminous and cannel coals Carnot 1 has found that certain parts
of plants, especially the spores, contain considerable phosphorous.
In a series of analyses he found in the Grande Couche, a thick seam
at Commentry, 0.00163 per cent of phosphorous; in the coal of Fer-
rieres 0.01385 per cent and in anthracite 0.01467 per cent of phos-
phorous. In several stems of typical Coal Measure plants changed
to coal he found from a trace to 0.007 per cent phosphorous. Various
cannels from England and central France were found to contain
considerably more of this element than the other coals, the percentage
varying from a trace to 0.028. Several bogheads gave 0.019 to 0.0627
per cent.

1 Carnot, Ad., Sur Porigine et la distribution du phosphore dans la houille et le cannel
coal. Compt. Rend., Vol. 99, pp. 154-156, 1884.

CALCIUM, MAGNESIUM AND IRON 37

For comparison the spores of several modern types of ferns related
to the Carboniferous plants were analysed and they contained from
0.078 to 0.228 per cent of phosphorous compared with 0.009 to o.oio
per cent for the body of the fern. The Ceratizamia mexicana yielded
0.28857 P er cent phosphorous from the pollen grains and 0.11899 P er
cent from the envelopes which had become fairly well separated from
the pollen grains. Mineral charcoal appears to be higher in phos-
phorous than the coal associated with it because during the change
from coal to mineral charcoal the phosphorous remained while vola-
tile constituents were lost, thus increasing the proportion of the former.

The alkalies and chlorine. Sodium chloride and other alkaline
salts may be carried into the coal in saline solutions which have
been derived from the surrounding rocks. The alkalies are derived
chiefly from the feldspars and related minerals and they are set free
by weathering of these minerals. The chlorine comes from plants
and from igneous rocks.

Silica. This compound enters the ash of the coal and is derived
chiefly from mineral matter deposited in the swamp by wind and
water both as mechanical sediment and in solution. It is, however,
derived partly from such plants as the horsetails which may contain
upwards of 12 per cent of it in their stems.

Calcium, magnesium and iron. All three of these elements may
be carried in solution as carbonates in the presence of carbon dioxide.
They may also be carried as sulphates and in small amounts as chlor-
ides. The iron in the form of sulphate or chloride on coming in con-
tact with a soluble salt, such as a salt of calcium, would normally
be thrown down as the hydrous oxide unless there were an excess
of carbon dioxide present to prevent oxidation in which case iron
carbonate might be precipitated instead of the oxide. The presence
of so much iron carbonate or " black band" associated with the
coal deposits in parts of America and England is explained
by assuming that the carbon dioxide, furnished by decomposing
vegetation, caused the iron to be precipitated as the carbonate (sider-
ite) rather than as the more commonly occurring hydrous oxide.

In addition to the elements mentioned there may be found in coal
ash, traces of gold, silver, zinc, lead, copper, titanium, vanadium,
manganese and a vast number of other elements of no particular
economic importance but of some scientific interest. Of these ele-

THE CHEMICAL PROPERTIES OF COAL

ments zinc has been found in wood, and manganese occurs up to
25.53 P er cen t as Mn 3 O4 in the ash from leaves of Norway spruce, and
41.23 per cent in the ash of the bark. Some Hawaiian pineapples
show 1.15 to 2.12 per cent Mn 3 O 4 . 1 It is thus evident that most of
the elements have been derived in part directly from the vegetation
and in part from solutions carried into the swamps.

The following table 2 illustrates the composition of the ash from
several types of trees and it shows that at least small percentages
of most of the elements may be supplied to the coal from the vegetal
matter which goes to form it. Some elements seem to be entirely
lacking in the ash of the common plants, while others are extremely
rare. For example, molybdenum and caesium are lacking while

ANALYSES OF ASH FROM TREES
(Dried at 105 in oven)

Birch Leaves
Per cent

Birch Stems
Per cent

Oak Leaves
Per cent

Oak Stems
Per cent

Pine Needles
Per cent

Pine Stems
Per cent

SiO 2

0.050

0.030

O.222

0.024

0.170

o .014

TiO 2

Trace

NF.

Trace

. OOOI

O.OOI

A1 2 3 ....

0.24

N.F.

0.038

0.070

0-253

0.090

Fe 2 3 . . .

0.29

0.015

0.023

O.O2O

0.016

MnO....

0.655

0.0098

0.160

0.0393

0.0596

O.OII

Cr,O 6 ....

N F.

N.F.

Trace

N.F.

Trace

N.F.

V 2 6

N.F.

Trace

N.F.

MoO 2 . . .

N.F.

CaO

i-4S

0.440

1.14

1-25

o 320

0.240

BaO

O.OI2

0.005

0.015

O.O20

0.005

0.007

SrO

0.006

0.004

0.013

0.023

0.003

0.004

MgO....

0-55

0.170

0.72

0.18

0.210

0.130

K 2 O

i-99

0.58

0.91

0.34

O.gi

0.30

Na 2 0....

O.IO

0.13

0.15

O.O7

0.07

Li 2 O ...

0.000047

0.00003

0.00015

o . 000003

O.OOOO6

. OOOI

Rb 2 O....

O.OOI

0.0003

O.OOOOI2

0.0015

O.OOOI5

N.F.

CS20. ...

N.F.

P 2 5 ....

i .10

0-33

0.261

0.274

0.27

0.075

SO 3

o-35

0.16

0-35

0.16

0.42

0.14

0.12

0.04

0.06

0.05

O.II

0.05

H 2 O.....

8.68

8.26

7-74

6.68

7.2

8.4

Mineral

constitu-

ents by

addition

5-8

4.0

2.6

2.8

i.i

1 Kelley, W. P., Manganese in some of its relations to the growth of pineapples. Jour.
Ind. & Eng. Chem., Vol. I, p. 533, 1909.

2 Robinson, W. O., Stemkoenig, L. A., and Miller, C. F., The relation of some of the
rarer elements in soils and plants. U. S. Dept. Agr., Bull. No. 600, Dec. 10, 1917.

CALCIUM, MAGNESIUM AND IRON 39

chromium and vanadium are very rare. It is evident that the high
percentage of vanadium in the ash analysis quoted below is due
entirely to some external source.

An analysis of ash from coal near the town of San Raphael in the
province of Mendozza, Argentina, gave the following results: 1

Soluble in Acids Percent Insoluble in Acids Percent

Vanadic acid 38 . 5 SiO 2 13.6

H 2 SO 4 12. i A1 2 O 3 5.5

P 2 O 5 0.8 Fe 2 O 3 9.4

Fe 2 O 3 4.1 MgO 0.9

A1 2 O 3 4.0

CaO 8.44

K 2 O i. 80

This coal contained 0.24 per cent of vanadic acid and this constitu-
ent was no doubt injected into the coal by solutions which percolated
through the. seam and which may have been derived from igneous
sources. Igneous rocks are the source of most of such rare constit-
uents in coal.

1 Mourlot, A., Analyse de la houille vanadifere. Compt. Rend., Vol. 117, pp. 546-
548, 1893.

CHAPTER III
CHEMICAL ANALYSIS OF COAL

Introduction

The analyzing of coal has long been recognized as the best laboratory
means of determining its commercial qualities. Much attention,
therefore, has been paid by chemists, geologists, and mining men,
to the various methods for obtaining samples and making analyses.
To be of any real value for purposes of comparison with other coals
or as a means of determining the commercial qualities of a seam the
coal analysed must be selected from the mine according to some
definite scheme. The uninitiated person invariably pays too little
attention to sampling and he very often picks out the best appearing
coal, thus deceiving not only his customers but himself regarding the
quality of the coal which is to be analysed. Too much attention
cannot be paid to the selection of samples which properly represent
the average composition of a coal seam or a shipment of coal.

Sampling for Analysis

The importance of a standard method. Different companies or
institutions may have their own methods of sampling, but it is de-
sirable that some uniform system be adopted for sampling coal in
all countries in order that the analyses made from the samples may
be available for comparative purposes. Much care has been taken
to standardize methods of analysis but much less attention has been
paid to standardizing methods of sampling. When a sample is
selected from a seam it should be taken in such a way that it will
represent the coal which will be mined. If a certain portion of the
parting is included in mining, this should also be included in the
sample. A standard of size for the material selected is also of im-
portance because the manner in which the portions of the seam
high in ash or low in ash break down on crushing will vary greatly.
This is owing to the varying character of the material constituting
bony streaks in the coal. In some places these may be sandy and in
others argillaceous. An analysis of the finely powdered material

THE IMPORTANCE OF A STANDARD METHOD 41

may differ distinctly from the lumpy portion, and standard crushing
and screening are therefore essential. The portion of the seam selec-
ted is a factor of importance because weathered coals differ in com-
position, heating value, and coking qualities from the unweathered
coal of the same seam owing to the effects of oxidation. The nature
of the roof and floor of the seam has an important bearing on the
probable weathered condition and in many places on the sulphur
content. Care should be taken, therefore, to observe faulted zones
and other disturbed areas. Examples are known where the coal
near the outcrop is higher in sulphur than that some distance under-
ground owing to the fact that, where the roof is fractured as a result
of weathering, sulphur compounds have been carried into the coal
from overlying pyrite-bearing rocks. The writer knows of one case
where the decision to purchase an important property on which the
coal was regarded as a high-sulphur type was based entirely on the
consideration of this phenomenon and the deal turned out very suc-
cessfully. In some mines there is much more sulphur in the "rolls"
under the seam than in the adjacent rocks and if water works through
fractures in these rolls the sulphur content may be increased in the
coal adjacent to them.

After the coal is obtained from the mine, car, or stock pile, care
should be taken to see that if it is not analysed at once it is kept in
air-tight receptacles in order that it may not lose or gain moisture,
lose gas or become oxidized. It is well known that coals lose a large
amount of methane on exposure to the atmosphere and take up oxy-
gen rapidly, especially just after removal from the seam, unless they
are carefully sealed. The altitude at which a sample is exposed to
the air also has a bearing on its composition since a marked change
in barometric conditions will affect the rate of evaporation of moisture
and the escape of gases.

United States Bureau of Mines and Geological Survey mine samp-
ling methods. In proceeding to sample a mine it is well to procure
a map if possible, so that the location where each sample is taken
may be properly fixed. The number of samples to be taken will
vary a great deal with the uniformity of the coal in a seam but about
four samples for a daily production of 200 tons or less, with an extra
sample for each additional 200 tons mined per diem, is considered
sufficient.

42 CHEMICAL ANALYSIS OF COAL

In taking the sample the United States Geological Survey and the
Bureau of Mines 1 recommend that a space 5 feet in width be cleared
of dirt and powder from top to bottom of the seam. Down the
center of this cleared space a zone i foot wide is cut to a depth of at
least i inch, in order to get perfectly clean coal behind that removed.
A cut is then made up the center of this zone to a depth of 2 inches
and a width of 6 inches or, if the coal be soft, to a depth of 3 inches
and a width of 4 inches. There should thus be obtained not less
than 5 to 6 pounds of coal for each foot thickness of the seam and
this should include, as nearly as possible, all bony coal retained in
mining operations, and it should exclude all partings discarded in
mining. It is suggested that in most places partings over f inch
thick, and sulphur balls, or other impurities, more than 2 inches in
maximum diameter and -| inch thick be omitted from the sample.

The sample taken as described above is collected on a collecting
cloth and then screened. The lumps are broken in a mortar and all
passed through a ^-inch or f-inch screen. The sample is thoroughly
mixed with the coarser materials evenly distributed. It is then
quartered and after remixing, it is requartered, if it be still too large
for convenient handling. The mixing complete, the sample is placed
in a can, the top screwed on and sealed with adhesive tape. The
can is carefully labeled with the name of the collector, the location,
the date, and all other information which might be of service when
the analysis is prepared. The government bureaus have prepared
very elaborate blank forms, which are filled out and shipped with
the cans.

Equipment for mine sampling. As equipment for the special
work of sampling, the following materials and tools have been sug-
gested: A portable mortar with sides 5 inches high and having a
capacity of 500 cubic inches; a pestle consisting of a steel head,
i inch thick and 3 to 4 inches long; a good spring balance of 50 pounds
capacity graduated to ^ pound; a galvanized iron wire screen of
f-inch mesh and provided with a wooden frame; a galvanized sheet-

1 Holmes, J. A., The sampling of coal in the mine. U. S. Bur. of Mines Tech. Paper
I, 191 1 ; Campbell, M. R., The commercial value of coal-mine sampling. Trans. Amer.
Inst. of Mng. Eng., Vol. 36, p. 341, 1906; The value of coal-mine sampling. Econ.
Geol. Vol. 2, p. 48, 1907; also Parr, S. W., Chemical study of Illinois coals. Illinois
Coal Mining Investigations. State Geol. Survey, Bull. 3, 1916.

SAMPLING WAGON, CAR, OR CARGO LOTS 43

iron scoop 8 inches long, 2 inches deep and ii inches wide, but a
trowel or shingle will serve in place of this; a stiff brush; a 2O-foot
waterproof measuring tape; a sampling can about 9 inches deep
by 3 inches in diameter made of No. 27 galvanized iron which is
crimped and soldered to make it strong and air-tight; adhesive tape;
a pick; and a shovel.

Sampling wagon, car, or cargo lots. In sampling wagon-loads,
carloads, or cargo lots of coal care should be taken to collect a repre-
sentative sample by choosing shovelfuls from different parts of the
load or pile and including an average amount of impurities. If the
coal be in coarse fragments, a larger sample should be collected than
if it be finely broken. About 1000 pounds should be taken as a gross
sample for carload or cargo lots and this should be increased to at
least 1500 pounds if the coal contains much impurity in coarse frag-
ments. It has been found that the analysis of a large gross sample
comes closer to the average for the lot than a small one, up to a certain
limit, above which there is no advantage in increasing the size of
the gross sample. 1

The looo-pound sample may be crushed so as to pass a i-inch
screen. It is then mixed, halved, by quartering method, and passed
through a f-inch screen. This process is continued until a 3o-pound
sample is obtained which will pass a T \-inch screen. After thorough
mixing and quartering a sample weighing 5 pounds is taken for an-
alysis.

From the tests of various coals by the United States Geological
Survey and Bureau of Mines it has been found that certain differences
exist between the analyses of mine samples and carload lots of the
same coal. These differences are due chiefly to oxidation and to
the changes in the moisture and gas content while exposed to the
atmosphere during transportation. The following statements apply
in most cases. In lignite and lignitic coals the moisture content is
greater in the car sample than in that taken in the mine and the de-
crease in calorific value may amount to 1.3 per cent in the moisture-
free and ash-free coal. If bituminous coals have a moisture content

1 Pope, G. S., Methods of sampling delivered coal. U. S. Bur. of Mines, Bulls. 63,
1913 and 116, 1916; Bailey, E. G., Accuracy in sampling coal. Jour. Ind. Eng. Chem.,
Vol. i, p. 1612, 1909; also Parr, S. W., Purchase and sale of Illinois coal on specification.
111. State Geol. Survey, Bull. 29, 1914. (Methods of Sampling.)

44 CHEMICAL ANALYSIS OF COAL

of over 5 per cent in mine samples they usually lose moisture in tran-
sit but they also lose calorific value from 0.3 to 0.8 per cent. Those
with less than 5 per cent usually show a gain in moisture up to about
1.5 per cent and the change in calorific value amounts to a very small
decrease. 1

Standard method of sampling. The Joint Committee of the
American Society for Testing Materials and the American Chemical
Society 2 suggests the following methods for sampling and the method
described in the final report of the Committee will hereafter be known
in this work as the standard method of sampling and analyzing coal.
It is insisted that the method outlined should be used in obtaining
a sample whether it is taken from a i-ton lot or from a lot containing
hundreds of tons. Also if this method is adopted in a contract the
following provisions shall be agreed upon (i) Place sampling is done,
(2) Approximate size of sample required when standard conditions
do not apply, (3) The number of samples to be taken or the amount
of coal to be represented by each sample when the standard con-
ditions (i.e. those outlined below) do not apply.

For the determination of all constituents except that of total
moisture the following regulations are observed (i) The coal is sampled
as it is loaded into or unloaded from conveyances or bins. If the
coal is crushed as received samples may be taken after the crushing.
Samples from the surfaces of piles are not reliable. (2) For taking
samples a shovel or specially designed tool capable of taking equal
portions of the coal shall be used. For slack or small sizes of an-
thracite increments as small as 5 to 10 pounds may be taken but for
run-of-mine or lump coal 10 to 30 pounds may be taken. (3) The
gross sample shall be not less than 1000 pounds and the increments
shall be so regularly and systematically collected that the entire
quantity of coal shall be properly represented in the sample. If
the fragments are small, not exceeding f inch in size a sample of 500
pounds is sufficient. If there is an unusual amount of slate or other
impurities or if the fragments are unusually large 1 500 pounds should

1 Campbell, M. R., Op. cit. Also Fieldner, A. C., Notes on the sampling and analysis
of coal. U. S. Bur. of Mines, Tech. Paper 76, 1914. For detailed descriptions of analyses
see: Methods of analyzing coal and coke, by F. M. Stanton and A. C. Fieldner, U. S.
Bur. of Mines, Tech. Paper 8, 1913.

2 American Society for Testing Materials, A. S. T. M. Standards, (D 21-16), 1918,
P- 673.

STANDARD METHOD OF SAMPLING 45

be taken. The following table shows the relation of the sizes of the
fragments of the coal to the weight of the sample taken. (4) A

TABLE A

Weight of sample to be divided.
In pounds

Largest size of coal and impurities in sample
before division. In inches

1000 or more

500

250

125
60

T \ or 4-mesh screen

gross sample shall be taken for each 500 tons or less, or in larger
tonnages according to agreement. (5) The gross sample shall be
systematically crushed, mixed and reduced in quantity to convenient
size for transmittal to the laboratory. The crushing may be done
by hand or by mechanical means, but loss and addition of foreign
matter must be prevented. (6) The progressive reduction of the
sample to the various quantities and sizes mentioned in the table
above shall be carried out in the following way : (a) The gross sample
is reduced to 250 pounds by the alternate shovel method observing
the requirements for relative sizes and weights in Table A, and div-
iding the coal as follows: The crushed coal is shoveled into a conical
pile by placing each shovelful on top of the one previously deposited
and then piling the coal in this pile in a long pile as wide as the shovel
and 5 to 10 feet long. This long pile is made by spreading each shovel-
ful out for the full width and length of the pile with alternate shovel-
fuls spread from opposite ends of the pile. The pile is flattened from
time to time. Half of this pile is discarded by beginning at the end
of the pile and taking shovelfuls side by side and one after the other
along the side of the pile. These alternate shovelfuls are placed in
two different piles and the operation continued until the long pile
is completely encompassed and practically all the coal divided be-
tween the two piles, (b) The sample now reduced to about 250
pounds is quartered, observing the relations outlined in Table A.
Quantities of 125 to 250 pounds are coned and re-coned while smaller
samples are placed on a cloth about 6 by 8 feet and mixed by raising
first one end and then the other so as to roll the coal back and forth.

46 CHEMICAL ANALYSIS OF COAL

By gathering the four corners of the cloth a conical pile is formed and
then quartered by first flattening down the apex uniformly and care-
fully and then dividing the pile into quarters so that the dividing
lines intersect at a point beneath the apex of the original cone. The
alternate quarters are discarded and the process described above is
repeated until a sample of about 30 pounds is secured, (c) The
3o-pound sample is crushed to T \ inch or 4-mesh size, mixed, flattened
and quartered. The laboratory samples shall include all of one of
the quarters or all of two opposite quarters if required and it is im-
mediately placed in a container designed for this purpose and sealed.
For the total moisture determination a special sample of about
100 pounds weight is made up by placing in a waterproof receptacle
equal parts of freshly taken increments of the standard gross sample.
This sample shall be rapidly crushed and reduced mechanically or by
hand to about 5 pounds. This smaller sample is at once sealed air-
tight in a container and sent immediately to the laboratory. The
standard gross sample shall not be used in place of this special moisture
sample unless equally representative results can be obtained from it.

Preparation of Laboratory Samples by Standard Method 1
Apparatus. (a) Jaw crusher for crushing coarse samples to pass
a 4-mesh sieve, (b) Roll crusher or coffee-mill type of grinder for
reducing samples to 2o-mesh. This mill should be entirely enclosed
and have an enclosed hopper capable of holding 10 pounds of coal.
(c) Abbe Ball Mill, Planetary Disk Crusher, Chrome-steel bucking
board or any satisfactory form of pulverizer for reducing the 2o-mesh
material to 6o-mesh. For the ball mill the porcelain jars should be
approximately 9 inches in diameter and 10 inches high. The flint
pebbles should be smooth and well-rounded, (d) Large Riffle sam-
pler with -j- or | -inch divisions for reducing the 4-mesh sample to
10 pounds, (e) Small Riffle sampler with J- or f-inch division for
dividing down the 20-mesh and 6o-mesh material to a laboratory
sample. (/) Eight-inch, 6o-mesh sieve with cover and receiver.
(g) Galvanized iron pans, 18 by 18 by ij inches deep for air-drying
wet samples, (h) Balance or solution scale for weighing the pans

1 Final report on coal analysis of the Joint Committee of the American Society for
Testing Materials and the American Chemical Society. Jour. Ind. and Eng. Chem.,
Vol. 9, No. i, p. 100, 1917. Also American Society for Testing Materials, A. S. T. M.
Standards (D 22-16), p. 679, 1918.

METHOD OF SAMPLING 47

and samples. (Required capacity 5 kilograms and sensitive to 0.5
gram.) (i) Air-drying oven to be used for drying wet samples.
Not absolutely necessary. (Description in Bull. No. 9, Geol. Survey
of Ohio, p. 312.)

Method of sampling. There are two methods, the choice de-
pending upon whether coal appears wet or dry.

I. When coal appears dry the first procedure is to reduce the coal
in the jaw crusher to pass a 4-mesh sieve and reduce the sample to
10 pounds weight, on the larger riffle sampler. (If crushed to pass
6-mesh the sample may be reduced to 5 pounds.) The lo-pound
4-mesh sample is ground in a roll crusher or coffee-mill to 2O-mesh.
From various parts of this sample, take with a spoon, without sieving,
a composite 6o-gram total-moisture sample which should be placed
directly in a rubber-stoppered bottle.

Thoroughly mix the main portion of the sample, reduce on the
smaller riffle sampler to about 120 grams and pulverize to 6o-mesh
by suitable grinder, disregarding loss of moisture. After passing
6o-mesh the sample is mixed and reduced to 60 grams on the small
riffle sampler. This final sample is transferred to a 4-oz. rubber-
stoppered bottle. Moisture is determined on both the 6o-mesh and
20-mesh samples. The following computation is made: The analysis
of the 6o-mesh coal which has become partly air-dried during samp-
ling is computed to the dry-coal basis by dividing each result by i
minus its content of moisture. The analysis of the coal " as received "
is computed from the dry-coal analysis by multiplying by i minus the
total moisture found in the 2o-mesh sample.

II. When coal appears wet the following method is followed:
The sample is spread on tared pans, weighed and air-dried at room
temperature, or in the special drying oven previously mentioned, at
10 to 15 C. above room temperature. It is weighed again. This
drying is continued until the loss of weight is not more than o.i per
cent per hour. The sampling is then completed as under I for dry
coal.

The following computation should be made: Correct the moisture
found in the 2O-mesh air-dried sample to total moisture "as received"
according to the following formula.

loo percentage of air-drying loss vx f r

X (percentage of moisture in

100

48 CHEMICAL ANALYSIS OF COAL

2o-mesh coal) + (percentage of air-drying loss) = (total moisture
"as received")- Compute the analysis to " dry-coal" and "as re-
ceived" bases as under dry coal, using for the "as received" compu-
tations the total moisture as found by the formula in place of the
moisture found in the 20-mesh coal.

Precautions: Owing to the fact that freshly mined or wet coal
loses moisture rapidly in the laboratory the sampling operations should
be carried out as quickly as possible between the time of opening the
container and the securing of the 2o-mesh sample and the sample
should be exposed to the air as little as possible. The accuracy of
the method of preparing the laboratory samples should be frequently
checked by using duplicate samples and by resampling rejected por-
tions of samples. The ash in two samples should not differ more than
the following amounts under the conditions stated: if no carbonates
are present 0.4 per cent; considerable carbonates and pyrite present
0.7 per cent; coals with more than 12 per cent ash, containing con-
siderable carbonate and pyrite i .o per cent.

English method. In the English government laboratories 1 the
coal is usually received in the laboratory in tins such as biscuit tins,
enclosed in wooden boxes, each sample weighing 20 to 30 pounds.
The sample is passed through a i-inch sieve, mixed thoroughly,
quartered and one-half returned to the tin. The other half is crushed
in a small Marsden-Blake crusher and by quartering reduced to about
i pound. It is then ground in a closely set coffee-mill and divided
into two parts, one of which is placed in a stoppered bottle and sealed
for future reference purposes, the other being placed in a similar bottle
for analysis. The sample taken from the coffee-mill is used for tests
on moisture and volatile matter but for other estimations a portion
is ground to pass a 5o-mesh sieve. The moisture is also determined
in the latter portion but the practice of determining the volatile mat-
ter in this portion also, has been discontinued as it has been found
that the results differ very little for the two samples.

The Proximate Analysis

The proximate analysis or the determination of moisture, volatile
matter, fixed carbon, ash and sulphur is the analysis usually made for
practical purposes since it is much more readily made than the ulti-
1 Pollard, W., Memoirs of the Geol. Survey, England and Wales, p. 6, 1915.

MOISTURE DETERMINATION

mate analysis and it furnishes most of the data necessary for the
purpose of arriving at the quality of the coal. From it the grouping
of the elements in the form most closely affecting combustion can be
determined.

Moisture determination by the standard method. Apparatus:
The apparatus recommended consists of the following articles: (i)
Moisture oven so constructed as to provide a minimum air space and a
uniform temperature in all parts of the chamber. The air in the
oven must be renewed 2 to 4 times every minute and the air must be
dried by passing it through sulphuric acid. (2) Capsules with covers
which permit the determination of ash in the same sample. Those
recommended are the Royal Meissen porcelain capsule No. 2, J inch
deep and if inches in diameter, or a fused silica capsule of similar
shape with a well-fitting flat aluminum cover. Glass capsules with
ground glass caps may also be used and they should be as shallow as
possible consistent with conven-
ient handling.

Method: (i) For determination
of moisture in the 6o-mesh sample
the empty capsules are heated
under the conditions at which the
coal is to be dried, then covered
and cooled over concentrated
sulphuric acid (sp. gr. 1.84) for
thirty minutes and weighed. Ap-
proximately i gram of the sample
is dipped from the bottle with a
spatula and placed in the capsules
which are immediately closed and
weighed.

The covers are removed and the
capsules quickly placed in a pre-
heated oven (at 104 to 110 C.) through which passes a current of
air dried by concentrated sulphuric acid. The oven is closed at
once and the specimens are heated for one hour. The oven is then
opened, the capsules quickly covered, and cooled in a desiccator over
concentrated sulphuric acid. When cool they are weighed and the
moisture computed.

FIG. 7. Moisture oven. (After Stan-
ton and Fieldner, U. S. Bureau of
Mines. Tech. Paper 8.)

50 CHEMICAL ANALYSIS OF COAL

(2) For the determination of moisture in the 2o-mesh sample
5-gram samples are used and they are weighed with an accuracy of 2
milligrams. They are heated for one and a half hours, otherwise
the procedure is the same as that described above for the 6o-mesh
sample.

Notes: The permissible differences in duplicate determinations are
as follows:

Same analyst

Different analysts

Moisture under 5 per cent
Moisture over 5 per cent

o . 2 per cent
o 3 per cent

0.3 per cent
o <? per cent

Determination of ash by the standard method. The ash in coal
or coke is a non-combustible mixture consisting of silicates of the
alkalies, calcium, magnesium, iron, and titanium; oxides of iron and
silicon; carbonates of iron, calcium and magnesium which may
change to oxides on heating; sulphates, the most common one being
that of calcium; phosphates; and arsenides. The color of the ash
is often an indication of its composition, as a pure white ash generally
indicates the absence of iron and a red ash its presence, although lime
may counteract the color of the iron and a cream-colored ash may
indicate the presence of both lime and iron. Effervescence with
acid shows that carbonates are present.

Apparatus: (i) A gas or electric muffle furnace. It should have a
good air circulation and be capable of maintaining a regular tempera-
ture between 700 and 750 C. (2) Porcelain capsules. Those rec-
ommended are the Royal Meissen No. 2, J inch deep and if inches
in diameter.

Method: The procelain capsules, containing the dried coal from
the moisture determination, are placed in a cold muffle furnace or on
the hearth at a low temperature and gradually heated to redness at
such a rate as to avoid loss of particles of the sample from the rapid
expulsion of the volatile matter. The ignition is finished when con-
stant weight is obtained (o.ooi gram) at a temperature between 700
and 750 C. The capsules are cooled in a desiccator and weighed.

Notes and precautions: The permissible differences in duplicate
determinations are as follows:

DETERMINATION OF ASH 51

Same analyst

Different analysts

No carbonates present

o . 2 per cent

o . 3 per cent

Carbonates present

0.3 "

o.<> "

Coal with more than 12 per
cent ash containing carbon-
ates and pyrite

0.5 "

Before the capsules are placed in the muffle for ignition to constant
weight the ash should be stirred with a platinum or nichrome wire.
Stirring once or twice before the first weighing hastens complete
ignition.

The result obtained as above is " uncorrected " ash. The mineral
matter in the ash differs materially from the actual minerals in the
coal.

Other notes and methods: Some analysts have used a platinum
crucible but this is not suitable for this purpose because, as stated
by Carnot, if a platinum crucible which contains carbon is heated
for some time a deposit of carbon and platinum dust may be made
which affects the weight of the ash. A platinum crucible should
never be used with coal containing pyrites. A coal high in pyrites
is liable to cause more trouble if heated too rapidly than one without
this mineral.

For the rapid determination of ash in coal, in the field, Lesher has
designed an apparatus for the use of the geologists of the United
States Geological Survey. By means of it the ash can usually be
determined within 2 per cent of the figures obtained by laboratory
methods. 1

There are often considerable errors in the result obtained in the
analyses of ash owing to the fact that the carbonates may change
to oxides or to sulphates, depending upon certain conditions. If a
carbonate changes to an oxide during combustion the carbon dioxide
driven off escapes and is lost to the ash while its carbon is computed
with the carbon, making it too high. This carbon is not in a com-
bustible form and therefore does not add to the value of the coal.
It will be seen that the oxygen is also affected by the error. Although
these errors in the determination of ash, carbon and oxygen, are not

1 Lesher, C. E., Field apparatus for determining ash in coal. U. S. Geol. Survey,
Bull. 62I-A, 1915.

CHEMICAL ANALYSIS OF COAL

considered in technical operation, where they are large they have an
important bearing on correct methods of analysis and on the heating
value of the coal. They have been fully discussed by a number of
writers and formulae have been suggested for their correction. 1

After the ash has been obtained from the coal, it may be analyzed
in much the same way as any other inorganic mixture.

The following figures show the composition of some typical coal
ashes:

Per cent

II.
Per cent

SiO 2

15.2-64.7
8.6-34.6
3.8-19.0
I .O-lS.I
0.4-10.0
0.3- 2.9
o-i- 5-3

- 2.6

Included with A1 2 O 3
0.1-26.9

45 . 24-50 . 23
23-43-33-28
5.50-14.68
2.76- 8.52
0.78- 2.88
-3-83

A1 2 O 3

Fe 2 O 3 . . .

CaO

MgO

K 2 O

Na 2 O

TiO 2

P 2 O 5

0.26- 1.85
0-96- 3.92

SO 3

Temperature of fusio

ii5o-i5oo C.

I. = Variations in composition shown in 9 analyses of ash from various types

of coals. Quoted by Fieldner, Op. cit., p. 29.

II. = Variations in composition shown in 4 analyses quoted by Carnot, Op. cit.,
p. 212.

The fusibility of the ash of coal is very variable. Like that of clay
it is lowered by the presence of such constituents as lime, iron, al-
kalies and magnesia. The temperature of fusibility is determined
by use of seger cones or the pyrometer. The ash itself may be molded
into a pyramid and the temperature at which the pyramid bends over
to its base is considered the point of fusibility. The more readily the
ash fuses the greater the difficulty arising from clinkers in the fur-
nace. The formation of clinkers can, however, be controlled to a
considerable extent by careful firing.

A list of analyses and the softening temperatures of a large number
of western coals is as follows. 2

1 Parr, S. W., Determination of ash. Jour. Ind. and Eng. Chem., Vol. 5, p. 523, 1913.
Fieldner, A. C., Op. cit., p. 27. Pollard, Op. cit., p. 40.

2 Selvig, W. A., Lenhart, L. R., and Fieldner, A. C., Temperatures at which ash from
western coals fuses to a sphere. Coal Age, Vol. 18, No. 14, p. 677, 1920.

DETERMINATION OF PHOSPHOROUS IN ASH 53

Average for samples tested:

Alaska 2040-3010 F. Nevada 2190-2480 F.

California 2220-2340 New Mexico 2000-3000 +

Idaho 1950-2640 Oregon 2060-2890

Montana 1930-2790 Utah 2040-2880

Washington 1870-3000 -f

Determination of phosphorous in ash by the standard method. I.

First method: The following method is to cover all cases: To the
ash from 5 grams of coal in a platinum capsule there is added 10 c.c.
of HNO 3 and 3 to 5 c.c. of HF. The liquid is evaporated and the
residue fused with 3 grams of Na 2 CO 3 . If unburned carbon is present
in the ash 0.2 grams of NaNO 3 is mixed with the carbonate. The
melt is leached with water and the solution filtered. The residue is
then ignited, fused with Na 2 CO 3 alone, the melt leached and the
solution filtered. The filtrates are combined, held in a flask, acidified
with HNOa and concentrated to a volume of 100 c.c. To this solution
raised to 85 C. there is added 50 c.c. of molybdate solution and the
flask is shaken for ten minutes. If the precipitate does not form
promptly and settle quickly, enough NH 4 NO 3 is added to cause it
to do so. The precipitate is washed six times or until free from acid,
with a 2 per cent solution of KNO 3 , then returned to the flask and
titrated with standard NaOH solution. The alkali solution may be
made equal to 0.00025 gram phosphorous per cubic centimeter, or
0.005 P er cent f r a 5- ram sample of coal and is 0.995 f one-fifth
normal. Or the phosphorous in the precipitate is determined by
reduction and titration of the molybdenum with permanganate.

The advantage in the use of HF in the initial attack on the ash
lies in the removal of silica. Fusion with alkali carbonate is necessary
for the elimination of titanium, which if present and not removed will
contaminate the phospho-molybdate and is said to sometimes retard
its precipitation.

II. Second method: Where titanium is so low as to offer no ob-
jection, the ash is decomposed in the same manner as in the first
method described above, but evaporation is carried only to a volume
of about 5 c.c. The solution is diluted with water to 30 c.c., boiled
and filtered. If the washings are turbid they are again passed through
the filter.

The residue is ignited in a platinum crucible, fused with a little

CHEMICAL ANALYSIS OF COAL

Na 2 CO 3 , and the melt is dissolved in HNO 3 . If the solution is clear it
is added to the main one but if not clear it is filtered. For the re-
mainder of the operation this method is the same as the first method.
The fusing of the residue may be omitted in routine work in a given
coal if it is certain that it does not contain phosphorous.

Determination of volatile matter by standard method. Apparatus:
(i) Platinum crucible with tightly fitting cover and a capacity of

not less than 10 c.c. nor more
than 20 c.c. Dimensions to be
not less than 25 nor more than
35 mm. in diameter and not
less than 30 nor more than 35
mm. in height. (2) A vertical
electric tube furnace, or a gas
or electrically heated muffle fur-
nace regulated to maintain a
temperature of 950 C. ( 20
C.) in the crucible as indicated
by a thermometer in the fur-
nace (Fig. 8). If the deter-
mination of volatile matter is

not an essential feature of the
specifications under which the
coal is bought a Meker burner
may be used.

Method: In a weighed plat-
inum crucible of 10 to 20 c.c.
capacity, closed with a capsule
cover, i gram of coal is placed.
The crucible is placed on platin-
um or nichrome-wire supports in the furnace chamber which must be
kept at 950 C. ( 20 C.). After the more rapid discharge of
volatile matter has subsided, as indicated by the dying down of the
flame, the cover is gently tapped to close the crucible more tightly, and
thus prevent the admission of air. The crucible is heated just
seven minutes and then removed from the furnace without dis-
turbing the lid. As soon as cool it is weighed. The loss of weight
minus moisture equals the volatile matter.

inum

\^ Platinnm-

" Rhodium

FIG. 8 Electric furnace for deter-
mination of volatile matter.

DETERMINATION OF VOLATILE MATTER 55

For subbituminous coal, lignite or peat, a modified method is
employed to avoid mechanical loss resulting from sudden heating of
these coals high in volatile matter. This consists in playing a burner
flame on the bottom of the crucible for five minutes thus gradually
heating it to a high temperature before it is placed in the volatile-
matter furnace. It is then heated in the furnace for six minutes at
950 C. as in the regular method.

Notes and precautions: The permissible differences in duplicate
determinations are as follows:

Same analyst

Different analysts

Bituminous coals

0.5 per cent

i o per cent

Lignites

TO "

20 "

The cover should fit close enough so that the carbon deposit from
bituminous coal or lignite does not burn away from the under. side of
the lid. Temperatures should be carefully regulated to the stand-
ards outlined.

Other methods: According to the preliminary report of the Joint
Committee 1 the method recommended was that in which the crucible
of 10 c.c. capacity was heated for seven minutes over a Bunsen burner
with the crucible 8 cm. above the mouth of the burner. The gas
pressure required was 50 mm. and the flame about 18 cm. in height.
The burner was to be surrounded with a refractory cylinder to pre-
vent air currents from disturbing the flame. The specifications for
the size of the crucible were: 2.4 cm., diameter at the base, 3.4 cm.
diameter at the top and 4 cm. high. This method is still used where
a suitable volatile-matter furnace is not available although a Meker
burner is more reliable. When this type of burner is used the crucible
is placed 2 cm. above the orifice with a flame 16 to 18 cm. high. A
No. 3 Meker is the type specified. These methods are not so reliable
as that with a proper furnace because of the varying conditions which
it is possible to have.

Carnofs method: Carnot, a French chemist, 2 suggests using 5
grams of coal in a platinum or porcelain crucible, the size of which

1 Jour. Ind. and Eng. Chem. Vol. 5, p. 517, 1913.

2 Carnot, Adolphe, Traite d'analyse des substances minerales, Vol. I and II, p. 205,
1904.

56 CHEMICAL ANALYSIS OF COAL

will depend upon the extent to which the coal is likely to swell. The
use of platinum should, however, be avoided if the coal contains
pyrite, and most coals carry some of this mineral although not always
in a megascopic condition. The crucible is covered with a closely
fitting lid and placed in a crucible of pottery with blocks of wood
charcoal surrounding it. The charcoal prevents the entrance of
oxygen on cooling. The clay crucible is covered with a lid, placed in
a calcination furnace, and heated for half an hour at a bright heat.
It is cooled, the small crucible wiped clean and weighed. Carnot
has also used a muffle furnace and, while he considers the Bunsen
burner method the simpler, he thinks that the results are more liable
to variation than those obtained by using a furnace.

Determination of fixed carbon by standard method. Fixed car-
bon is always determined by difference as follows: 100 (per-
centage moisture + percentage ash + percentage volatile matter)
= fixed carbon.

Determination of sulphur by the Eschka method. 1 While such
a method as the calorimeter method may be used for purposes of
control in such a laboratory as the fuel-inspection laboratory of the
United States Bureau of Mines no other method is considered quite
so reliable as the Eschka method although it is not so rapid as some
of the others.

Apparatus: (i) Gas or electric muffle furnace, or burners for
igniting the coal with the Eschka mixture arid for igniting the barium
sulphate. (2) Porcelain, silica or platinum crucibles or capsules for
igniting coal with the Eschka mixture. (3) No. i Royal Meissen
porcelain capsule i inch deep and 2 inches in diameter. This capsule
presents more surface for oxidation and it is more convenient to
handle than the ordinary crucible. (4) No. i Royal Berlin porcelain
crucibles of shallow form and a platinum crucible of similar size
may be used. (5) No. o or oo porcelain crucibles or platinum, alun-
dum or silica crucibles of similar size must be used for igniting the
barium sulphate.

Solutions and reagents: (i) Barium chloride. Dissolve 100 grams

of barium chloride in 1000 c.c. of distilled water (2) Saturated

bromine water. Add an excess of bromine to 1000 c.c. of distilled

water. (3) Eschka mixture. Thoroughly mix 2 parts ; by weight,

1 Oesterreichische Zeitschr. XXII, p. in, 1874.

DETERMINATION OF SULPHUR tf

of light calcined magnesium oxide and i part of anhydrous sodium
carbonate. Both materials should be as nearly as possible free from
sulphur. (4) Methyl orange; Dissolve 0.02 gram in 100 c.c. of
hot distilled water and then filter. (5) Hydrochloric acid. Mix
500 c.c. of hydrochloric acid (Sp. gr. 1.20) and 500 c.c. of distilled
water. (6) Normal hydrochloric acid Dilute 80 c.c. of hydro-
chloric acid (Sp. gr. 1.20) to i liter with distilled water. (7) Sodium
carbonate. A saturated solution taking approximately 60 grams of
crystallized or 22 grams of anhydrous sodium carbonate in 100 c.c.
of distilled water. (8) Sodium hydroxide solution. Dissolve 100
grams of sodium hydroxide in i liter of distilled water. This solution
may be used in place of the sodium-carbonate solution.

Standard Method: Thoroughly mix on glazed paper i gram of coal
and 3 grams of Eschka mixture. Transfer the mixture to a No. i
Royal Meissen capsule, a No. i Royal Berlin crucible, or a platinum
crucible of similar size. Cover with about i gram of Eschka mixture.
Ignition shall be performed by heating the crucible over an alcohol,
gasoline, or a natural gas flame or in a gas or electrically heated muffle.
Artificial gas must not be used owing to its sulphur content, unless
the crucible is heated in a muffle. When heated over a flame the
crucible is placed in a slanting position on a triangle over a very
low flame. This is necessary to avoid rapid expulsion of volatile
matter which tends to prevent complete absorption of the products
of combustion of the sulphur. The crucible is heated slowly for
thirty minutes, the temperature being increased gradually and the
mixture being stirred after all black particles have disappeared. The
latter condition indicates the completeness of the operation.

If the crucible is heated in a muffle, it should be placed in a cold
muffle and the temperature gradually raised to 87o-975 C. (cherry-
red heat) in about one hour. This maximum temperature is main-
tained for about ij hours and the crucible is then allowed to cool in
the muffle.

After cooling, the contents are emptied into a 200 c.c. beaker and
digested with 100 c.c. of hot water for one-half to three-quarters of an
hour with occasional stirring. The solution is filtered and the residue
washed by decantation. After several washings insoluble matter is
transferred to the filter and washed five times, the mixture being
kept well agitated. The filtrate amounting to about 250 c.c. is

58 CHEMICAL ANALYSIS OF COAL

treated with 10 to 20 c.c. of saturated bromine water which is then
made slightly acid with hydrochloric acid and boiled to expel the
liberated bromine. The so ution is then made just neutral to methyl
orange either with sodium hydroxide or sodium carbonate solution
and i c.c. of normal hydrochloric acid is then added. It is boiled
again and 10 c.c. of a 10 per cent-solution of barium chloride (BaCl 2 -
2H 2 O) is added slowly from a pipette with constant stirring. The
boiling is continued for fifteen minutes and the solution allowed to
stand for at least two hours, or better over night, at a temperature
just below boiling. It is filtered through an ashless filter paper and
washed with hot distilled water until a silver nitrate solution shows
no precipitate with a drop of the filtrate. The wet filter containing
the precipitate of barium sulphate is placed in a weighed platinum,
porcelain, silica or alundum crucible, free access of air being allowed
by folding the paper over the precipitate loosely so as to prevent
spattering. The paper is smoked off gradually and at no time al-
lowed to burn with flame. After the paper is practically consumed the
temperature is raised to approximately 925 C. and heated to constant
weight.

The residue of magnesia, etc., after leaching should be dissolved
in hydrochloric acid and very carefully tested for sulphur. If an
appreciable amount is found it should be determined quantitatively
as the amount of sulphur obtained is important.

Blanks and Corrections: A correction must always be applied
either (i) by running a blank exactly as described above using the
same amount of all reagents that were employed in the regular de-
termination, or more surely (2) by determining a known amount of
sulphate added to a solution of the reagents after these have been put
through the prescribed series of operations. If the latter procedure
is adopted and carried out once a week or whenever a new supply of
a reagent must be used and for a series of solutions covering the
range of sulphur content likely to be met with in coals, it is only
necessary to add to or subtract from the weight of barium sulphate
obtained from a coal, whatever deficiency or excess may have been
found in the appropriate " check" in order to obtain a result that is
more certain to be correct than if a " blank" correction as determined
by the former procedure is applied. This is due to the fact that the
solubility error for BaSO 4 for the amounts of sulphur in question and

SULPHUR DETERMINED BY THE BOMB CALORIMETER 59

the conditions of precipitation prescribed, is probably the largest
one to be considered. BaSO 4 is soluble in acids and even in pure
water and the solubility limit is reached almost immediately on
contact with the solvent. Hence, in the event of using reagents
of very superior quality or of exercising more than ordinary precautions
there may be no apparent " blank" because the solubility limit of
the solution for BaSO4 has not been reached or, at any rate, not
exceeded.

The Atkinson and sodium-peroxide methods give results similar
to those obtained by the Eschka method. According to Register if
5 per cent of nitrogen is present in the gases contained in the bomb
calorimeter, the sulphur of a coal is almost completely oxidized to
H 2 SO4 and the washings of the calorimeter may be used for the de-
termination of sulphur.

The permissible differences in duplicate determinations are as
follows :

Same analyst

Different analysts

Sulphur under

2 per cent

o 5 per cent

o 10 per cent

Sulphur over 2

per cent

O.IO "

o . 20 "

Sulphur determined by the bomb calorimeter. To determine the
sulphur content of a coal by means of the bomb calorimeter the
washings from the calorimeter are collected in a 250 c.c. beaker.
The solution is titrated with standard ammonia (0.00587 gram per
c.c.) to make the "acid correction" for the heating value, methyl
orange being used as an indicator. To this solution is added 5 c.c.
of dilute hydrochloric acid (1:2) and it is then raised to the boiling
point before filtering off any insoluble matter. After thorough wash-
ing, the filtrate is boiled and the sulphur precipitated with barium
chloride as in the Eschka method. The percentage of sulphur is
then derived as follows:

Weight of BaS0 4 X 13. 74

' TTT 14. i * = percentage of sulphur.
Weight of sample

The results obtained by the calorimeter are usually 3 to 8 per
cent lower than those by the Eschka method. (For a further note
on this method see discussion under "The bomb calorimeter. "

CHEMICAL ANALYSIS OF COAL

The calorimetric method is recommended by Parr 1 who also uses
it for sulphur in coke. The coke is pulverized and burned in the
Parr peroxide calorimeter with sodium peroxide and the sulphur
determined in the washings.

The Photometric Method with Turbidimeter. There are many
variations of the photometric method but they can only be used for
rough determinations. One apparatus which seems to give satis-
factory results is a modified form of the Jackson candle turbidimeter
(Fig. 9). This is one type of the turbidimeter which is being adop-
ted by many analysts for rapid determinations of sulphur in control
work. The principle of this apparatus is a
brass stand, in the center of the base of which
there is a holder for an English standard
candle. This candle is regulated so that a
flame 30 to 40 mm. long is maintained.
Above this candle is a horizontal support with
a hole in the center. Over this hole a grad-
uated glass cylinder with flat polished bottom
is placed in a vertical, opaque cylinder more
than half the height of the glass vessel.
Since this apparatus is used mainly for rapid
water analysis 2 the vessel is graduated so
that the lines correspond to turbidities pro-
duced in distilled water by silica when present
in certain parts per million. A 25-centimeter tube may show tur-
bidities of 100 to 5000 parts per million of silica and a 75-centimeter
tube 25 to 5000 parts per million.

The early designs of this instrument were not very satisfactory for
the determination of sulphur, but after an extended series of experi-
ments Muer 3 found that with certain revised tables quite satisfactory
results could be obtained. A series of experiments by this modified
method gave results which compare favorably with those obtained
by the gravimetric method. The method as outlined as is follows:
The washings from the bomb calorimeter amounting to about 150 c.c.

1 Parr, S. W., Composition and character of Illinois Coals. 111. State Geol. Survey,
Bull. 3, p. 55, 1906.

2 U. S. Geol. Survey, Water supply and irrigation paper No. 651, 1905.

3 Muer, H. F., The determination of sulphur in coal by means of Jackson's candle
turbidimeter. Jour. Ind. and Eng. Chem., Vol. 3, p. 553, 1911.

FIG. 9. Jackson's candle
turbidimeter.

THE PHOTOMETRIC METHOD WITH TURBIDIMETER 6l

are filtered and then titrated with N/io sodium carbonate, using
methyl orange as indicator. The titrated solution is then made up
to 200 c.c. The acidity of the solution may be taken as an index
of the amount of solution to be taken for the sulphur test. For
anthracite the proportion taken is i to and for soft coals J to T V
of the whole. This portion of the solution is measured in the turbidi-
meter tube diluted to near the 100 c.c. mark on the tube. It is shaken,
acidified with i c.c. of i : i hydrochloric acid and made up to the
100 c.c. mark. It is mixed thoroughly by shaking. A tablet of
barium chloride, weighing i gram and having been compressed without
the use of a binder is placed in the solution. The barium chloride
in this particular form seems to give the most finely divided precip-
itate and therefore the best results. After the tablet is placed in
the tube the latter is closed by a clean rubber stopper and then rolled
gently until the precipitation of the sulphur is complete. The turbid
liquid is transferred to a beaker. The candle is lighted, the gradu-
ated tube is put in place, and enough of the liquid is at once poured
in to prevent the tube from cracking. The liquid is then gradually
poured in, being allowed to run down the side of the tube, until the
flame becomes dim as one looks down the tube. The liquid is then
added very slowly until the flame just disappears. The depth of the
liquid in centimeters is noted, the liquid returned to the beaker and
a new reading made. This process is repeated until a good average
reading is obtained. Knowing the depth of the liquid in centi-
meters the weight of sulphur and sulphur trioxide in milligrams may
be obtained from a table which Muer has prepared. In his experi-
ments he found that for a depth of less than 2.5 cm. of liquid there
was a sharp deviation from a straight line curve in which the increase
in depth in centimeters was inversely proportional to the weight of
sulphur in milligrams. This variation seems to be due to the lens
effect of the bottom of the tube and to avoid it the solution should
be diluted so that the depth will be greater than 2.5 cm. For depths
above 17.0 cm. there was also a marked variation from the straight
line and to avoid this it is better to concentrate the solution. For
all readings between these two limits it was found that the following
formula is applicable:

62 CHEMICAL ANALYSIS OF COAL

where S is the weight of sulphur in milligrams and C is the depth of
the liquid in centimeters at the time the flame becomes obscured.

Methods for determining the proportions of the various forms of
sulphur in coal. In a recent article Powell and Parr 1 have enumer-
ated methods for determining the proportions of the various forms
of sulphur in coal, as follows : For sulphate sulphur the coal is treated
with hydrochloric acid after fine grinding. A sample of 5 grams is
treated with 300 c.c. of a 3-per cent solution of the acid, for forty
hours at 60 C. The solution is filtered and the filtrate analyzed for
sulphur as in the regular method by precipitation with barium chlo-
ride (BaCl 2 ). For the pyrite sulphur determination the sulphate
sulphur is first removed as described above with hydrochloric acid
and the coal is then treated with nitric acid. A i-gram sample of the
finely powdered coal is employed and about 80 c.c. of nitric acid
(i part HNOs sp. gr. 1.42 to 3 parts water, resulting sp. gr. about
1.12) is used. The solution stands at room temperature for twenty-
four hours before being filtered. The nitric acid is disposed of by
evaporating the filtrate to dryness and after taking up with a little
hydrochloric acid the sulphur is precipitated by barium chloride
(BaCl 2 ).

The resinic sulphur is determined by treating the coal with phenol:
this treatment involves prolonged extraction with this reagent. The
other form of organic sulphur, known as the humus sulphur, is de-
termined directly by taking the residue from the nitric acid extraction
and adding 25 c.c. ammonium hydroxide (sp. gr. 0.90). This mix-
ture is allowed to stand for several hours; it is then diluted, passed
through a large filter and the filtrate evaporated to dryness. The
sulphur may then be determined in the usual manner by fusing the
residue with sodium peroxide. It is evident that the total organic
sulphur may be determined by subtracting the sum of the sulphate
and pyrite sulphur determinations from the total sulphur, or the
humus sulphur might be determined by difference between total sul-
phur and the sum of the other three types.

Sulphur in ash. A determination of sulphur in the ash may be
made by placing the ash in an evaporating dish, adding hydrochloric
acid, evaporating to dryness, then taking up with hydrochloric acid

1 Powell, A. R., and Parr, S. W., Forms in which sulphur occurs in coal. Trans.
Amer. Inst. Min. Met. Eng., Vol. LXIII. p. 674, 1920.

DETERMINATION OF CARBON AND HYDROGEN

and hot water. This solution is
filtered and, after washing, the sul-
phur is precipitated as barium sul-
phate (BaSO 4 ) by adding barium
chloride (BaCl 2 ). From the result
obtained the combustible sulphur in
the coal may be determined by sub-
tracting the above result from the
total sulphur. 1

Ultimate Analysis

Determination of carbon and hy-
drogen. The determination of car-
bon and hydrogen is made with a
combustion furnace, either gas or
electric. The gas furnace used is
usually the Glaser type with twenty-
five burners. The Fletcher furnace
is often used in England. The prin-
ciple involved is the complete oxida-
tion of the carbon and hydrogen by
passing the products of combustion
over red-hot copper oxide. The sul-
phur is taken up by lead chromate.

Description of the furnace: The
apparatus consists of a purifying
train in duplicate, a combustion tube
and an absorption train (Fig. 10).
The purifying train is in duplicate
so that oxygen may be fed from a
gas vessel, such as a Linde oxygen
cylinder, through one set of tubes
and air through the other. It is
connected to the combustion tube by
a three-way tap so that the currents
may be regulated. The air and oxy-
gen are first passed through sul-

1 Pollard. Op. cit., p. 9.

64 CHEMICAL ANALYSIS OF COAL

phuric acid, then through a 30 per cent potassium hydroxide solution,
then over soda lime and granular calcium chloride in a U-tube.
Some English analysts use two U-tubes filled with pumice saturated
with sulphuric acid, the pumice having previously been ignited with
sulphuric acid to remove chlorides and other impurities, in place of the
soda lime and calcium chloride tube A small bottle of sulphuric
acid may be connected in series next to the combustion tube for the
purpose of indicating the rate at which the gases are being fed to
the combustion tube.

The combustion tube should be from 100 to no cm. in length by
about 21 mm. in external or 12 to 15 mm. internal diameter. It
should be of hard Jena or similar glass.

The absorption train consists of a Marchand tube filled with gran-
ular calcium chloride (CaCl 2 ) for absorption of the water. Instead
of this material a U-tube filled with pumice saturated with sulphuric
acid may be used. If the acid be used it is well to fill the tube, allow
it to stand over night and then drain off the acid just before using.
Following the Marchand tube there is a Liebig or Geissler bulb filled
with 30 per cent potash solution to absorb the carbon dioxide given
off. This solution should be treated with a little potassium perman-
ganate for the purpose of oxidizing any ferrous iron or nitrates. In
place of this solution powdered potash is often used. A guard tube
comes next and is filled with soda lime and granular calcium chloride
so as to absorb any traces of carbon dioxide and moisture which have
passed the other tubes. Some analysts use sulphuric acid and pumice
for this purpose.

Testing the apparatus: To prepare the apparatus for a determin-
ation care should be taken to see that all the reagents used are fresh
and pure. A blank test may be run by passing about a liter of air
through the train, heated as in a regular test; if there is a change in
weight in the absorption tubes of less than 0.5 mg. each the apparatus
is considered ready for use.

Method of making the determination with furnace: The sample of
dry coal ground to 50 or 6o-mesh is weighed into a platinum or por-
celain boat. The weight of the sample used varies with different
analysts, some considering that a o. 5-gram sample is best while others
use a o.2-gram sample. The latter is recommended by the analysts
of the United States Bureau of Mines. The boat containing the

DETERMINATION OF. CARBON AND HYDROGEN 65

sample is kept in a weighing tube to exclude moisture while prepar-
ations are being made for placing it in the combustion tube.

The combustion tube is filled in different ways by different analysts.
For example, Pollard leaves a space of 10 cm. at each end of the tube.
The space is followed by 6-8 cm. of copper-oxide roll; 16-20 cm.
for the boat; 45 cm. of copper oxide; 8 cm. lead chromate; and
10 cm. of silver spiral. Stan ton and Fieldner leave the first 30 cm.
of the tube empty. This space is followed by an asbestos, acid-
washed and ignited plug, or a roll of copper gauze. Following
this is 40 cm. filled loosely with copper-oxide wire. The wire is
separated from 10 cm. of lead chromate by another asbestos plug.
A third asbestos plug 20 cm. from the end of the tube keeps the
chromate in place.

The combustion tube containing the boat in which the coal is spread
out flat is connected in the train and the train is connected with an
aspirator which produces a steady suction. The suction may be
kept constant by using a Mariotte flask. It is easier to keep the
joints tight if the gases be drawn through the apparatus than if they
be forced through by pressure. A satisfactory test for the tightness
of the apparatus is to draw air through the potash bulb at the rate of
three bubbles per second. The three-way tap is then closed and if
not more than three bubbles of gas pass the potash bulb per minute
it is considered satisfactory.

When the boat is placed in the combustion tube care must be taken
to have the copper oxide at a bright red heat and the lead chromate
at a dull red before the coal is heated. Otherwise methane may
escape combustion. Before the coal is heated a current of oxygen
is passed. The coal must be heated gradually; otherwise too much
tarry matter may be driven off in a short space of time to permit
complete combustion. The heat is increased gradually and the cur-
rent of oxygen is maintained for about two minutes after the sample
ceases to glow when it is turned off and about 1200 c.c. of air is drawn
through the train.

The absorption bulbs or tubes are disconnected and weighed.
The hydrogen percentage in a o. 2-gram sample is determined by
multiplying the increase in weight in the calcium chloride tube by
55.55 and the carbon percentage by multiplying the increase in
weight in the potassium hydroxide bulb by 136.36. It is evident that

66 CHEMICAL ANALYSIS OF COAL

the percentage of carbon will vary slightly if there are carbonates in
the coal and the hydrogen will vary if there are hydrous minerals or
moisture present.

The ash in this sample may be weighed and its percentage also
determined. Duplicates should agree within o.i per cent for hy-
drogen and 0.2 per cent for carbon.

A convenient electric furnace of the Heraeus type may be used
in place of the gas combustion furnace. This furnace as used by
Stanton and Fieldner 1 consists of three independent heaters. Two
of these are on wheels and mounted on a track so that they are mov-
able. The third one is stationary around the tube where the lead
chromate is located. The stationary heater is not a part of the
regular Heraeus furnace but it was added by winding an alundum
tube 12 cm. long with No. 16 nichrome II wire and enclosing it in a
cylinder packed with magnesia-asbestos.

The movable heaters have very thin platinum foil, weighing about
9 grams in all, wound on a porcelain tube of 30 mm. internal diameter.
The combustion tube is about 21 mm. external diameter and 900
mm. in length. It consists of Jena glass or fused silica. It is sup-
ported in an asbestos-lined nickel trough. Each heater has a separate
rheostat and the current required is about 4.5 amperes with 220
volts.

The purifying train consists of a Tauber s drying apparatus which
contains sulphuric acid, a 30 per cent potassium hydroxide solution
of granular soda lime and calcium chloride. The absorption train
consists of a 5 -inch U-tube containing granular calcium chloride;
a Vanier potash bulb containing a 30 per cent potassium hydroxide
solution and granular calcium chloride; a guard tube, containing
granular calcium chloride and soda lime; and a Mario tte flask for
preserving a constant pressure. The calcium chloride used in the
tube should be saturated with carbon dioxide before using by being
placed in a large drying jar and having the jar filled with carbon
dioxide. The jar is left over night and dry air is then drawn through
it to remove the carbon dioxide. The saturated material may then
be kept in tightly stoppered bottles.

It is possible with this furnace to so adjust the heaters that the
tube may be dried carefully, the lead chromate may be kept hot and

1 Op. cit., p. 22.

DETERMINATION OF CARBON AND HYDROGEN

6 7

the copper oxide may be raised to a red heat before the boat con-
taining the sample is heated to a high temperature. The boat is
then heated until all the carbon is burned off as indicated by the fact
that the residue ceases to glow. The tubes are then weighed and the
calculation made as in the determination described above with the
gas combustion furnace.

In addition to the methods described above Parr 1 has described a
process for determining total carbon with the improved Parr Calor-
imeter.

A description of this calorimeter is as follows: A A (Fig. na), is
a liter can for water; BB and CC are insulating vessels of indurated
fiber; D is a cartridge to receive the charge of coal and chemicals.

Fig. ii. (a) Parr peroxide bomb calorimeter. (V) Bomb enlarged.

It rests on the pivot F and is made to revolve by means of the pulley P.
The small turbine wings produce complete circulation of the water.
The temperature is recorded on the thermometer T. Figure nb is
an enlargement of the bomb or cartridge which has been improved
by placing the air chambers around the inner shell. These chambers
contain air which the sudden rise in temperature expels. The air

1 Op. cit.

68 CHEMICAL ANALYSIS OF COAL

at first prevents the cooling of the sides of the chamber to such a
point that the chemical action around the walls is checked and then
on being expelled it permits the cooler water to come into contact
with the hot walls of the shell and produce a more rapid transfer
of heat and consequently greater efficiency.

Parr used sodium peroxide and the reaction is approximately as
follows:

56 Na 2 O 2 + C 25 Hi 8 O3 = 25 Na 2 CO 3 + iSNaOH + 22Na 2 O.

Sodium Coal Sodium Sodium Sodium

peroxide carbonate hydrate oxide

For such substances as coke, petroleum, and anthracite a more
vigorous oxidizing medium is used. The most effective is a mixture
of potassium chlorate and nitrate in proportion of i to 4 and used
with sodium peroxide in proportion of i to 10. This was used to
good advantage on the slaty coals.

Parr devised this method in order that there might be some ready
means of obtaining the total carbon as this was necessary in his
classification of coals. He also devised a curve from which can be
read the percentage of combustible or available hydrogen when the
carbon content is known. The curve is based on the principle that
there is a more or less definite relation in the various coals between
the total carbon, the fixed carbon, and the " available" hydrogen.
(For a discussion of the subject of available hydrogen in coal, see
Parr's Classification in Chapter 5.)

The determination of nitrogen. The method usually employed
for the determination of nitrogen is the modified Kjeldahl- Gunning
method. 1 A gram of coal is placed in a 500 c.c. Kjeldahl flask to-
gether with 30 c.c. of concentrated sulphuric acid, 5 to 8 grams of
potassium sulphate (K 2 SO4) and 0.6 grams of mercury. Mercury
oxide may be used instead of mercury, but a gram of the oxide is
necessary. The solution should be boiled until the coal is all oxi-

1 Dyer, B., Kjeldahl's method for the determination of nitrogen. Jour. Chem. Soc.,
Vol. 67, pp. 811-817, l8 95- Also, Trescot, T. C., Comparison of the Kjeldahl-Gunning-
Arnold method with the official Kjeldahl and official Gunning method of determining
nitrogen. Jour. Ind. Eng. Chem., Vol. 5, pp. 914-915, 1913 and Wedemeyer, K., Ein
Wort zur Stickstoffbestimmung nach Kjeldahl-Gunning. Chem. Ztg. Jahrg. 22. p. 21,
1898.

THE DETERMINATION OF NITROGEN 69

dized and the solution has become practically colorless. The boiling
may require two hours or more, depending upon the nature of the
coal. The solution is allowed to cool and a little potassium perman-
ganate (K Mn O 4 ) is added or it may be added without cooling.
Some analysts add this while the solution is hot, while others cool
it first. After boiling for an hour, the permanganate is added to-
gether with more mercury and then boiled again until complete
oxidation results.

The solution is cooled and diluted to about 200 c.c. with cold water.
To this is added 20 to 25 c.c. of potassium sulphide (K 2 S) solution
(40 grams per liter) to precipitate the mercury. Sodium sulphide
(Na 2 S) of same strength is sometimes used in place of the potassium
sulphide. A little zinc is added to prevent bumping and then about
80 to 100 c.c., or enough to make the solution alkaline, of a 50 per
cent solution of sodium hydroxide (NaOH). The Kjeldahl flask is
at once connected with the condenser and the ammonia is distilled
over into a measured amount (usually 10 c.c.) of standard sulphuric
acid, to which cochineal indicator is added for titration. The dis-
tillation is continued until about 200 c.c. has passed over. The
distillate is then titrated with standard ammonia solution. (In this
case 20 c.c. NH 4 OH = 10 c.c. H 2 SO4 = 0.05 grams nitrogen.)

Pollard 1 states that the following modification was used in the
English Government laboratory with good results, a sharper end-
point being obtained by this method than in the former practice.
The duplicates agreed to within 0.05 per cent. To i gram of coal
30 c.c. of pure, concentrated sulphuric acid containing i gram of
salicylic acid was added. The vessel was kept cool by being im-
mersed in water while the acid was added. To this solution 5 grams
of sodium thiosulphate were carefully added and then 7 grams of
potassium sulphate, followed by a crystal of copper sulphate. This
mixture was heated gradually at first and then strongly until complete
oxidation occurred. It was cooled, and distilled with excess of soda
and a little sodium sulphide in the usual way, into 25 c.c. of N/io
sulphuric acid. The excess of soda was determined by adding to the
solution 10 c.c. of a 10 per cent solution of potassium iodide, the
liberated iodine being determined in the usual way. Pollard's use
of copper sulphate is interesting in view of the fact that Fieldner and

1 Op. cit., p. 9.

70 CHEMICAL ANALYSIS OF COAL

Taylor 1 found that copper sulphate was not as good a catalytic agent
as mercury.

The determination of oxygen. A great many different analytical
methods have been suggested for the determination of oxygen but
none of them are sufficiently simple or accurate to be generally ac-
cepted. 2 The scheme almost universally adopted is to obtain oxy-
gen by difference, the sum of carbon, hydrogen, nitrogen, sulphur, and
ash being subtracted from 100 per cent. This has one great disad-
vantage because it throws upon the oxygen the accumulated errors
in the determination of carbon, hydrogen, nitrogen, sulphur and ash.
These errors may tend to balance one another to some extent but
there are many indefinite factors which may affect the result. If the
coal contains iron pyrite this tends to make the oxygen too low; if
it contains argillaceous materials, which would naturally carry water
of composition, the oxygen in the coal will be too high. 3 Carbonates
from the coal, as already pointed out, will have a bearing on the
proportions of oxygen and carbon in the coal. This is because there
is no means, with our present methods, of distinguishing between
the carbon and oxygen from the coal and that from the carbonates
unless an analysis of the ash be made and the various constituents
computed in terms of carbonates, sulphides, etc., an operation which
cannot be carried out in practice.

Some of the methods used for the direct determination of oxygen
in coal are based on the following principles: Baumhauer 4 en-
deavored to reoxidize the copper reduced in the combustion tube.
He also employed iodate of silver. Mitscherlich 5 has used at different
times a current of chlorine which united with hydrogen to form
hydrochloric acid, leaving the oxygen free or to unite with carbon,
and mercury dioxide. Since a certain amount of oxygen must be
supplied in addition to that in the coal in order to produce complete

1 Fieldner, A. C., and Taylor, C. A., Determination of nitrogen in coal. U. S. Bur.
of Mines, Tech. Paper 64, p. 22, 1915.

2 For a good summary of various methods see Carnot, Op. cit., p. 229.

3 Parr, S. W., An initial coal substance having a constant heating value. 111. State
Geol. Survey ; Bull. 8, 1907.

4 Baumhauer, E.H.V., Ueber die Elementaranalyse organische Korper. Zeitschr.
f. Analyt. Chem., Vol. V, p. 143, 1866.

8 Mitscherlich, A., Neue Methoden zur Bestimmung der Zusammensetzung organischer
Verbindungen, Zeitschr. f. Analyt. Chem., Vol. VI, p. 136, 1867.

DETERMINATION OF THE CALORIFIC VALUE 71

combustion it is supplied by the mercury dioxide and its weight can
be determined.

Maumene 1 has employed litharge and calcium phosphate and has
calculated the oxygen supplied by the litharge for combustion of
the organic material.

Determination of the Calorific Value

The calorific value of a coal is the heat developed by the com-
bustion of a unit weight of the substance. It is usually expressed in
terms of the calorie or the British thermal unit (B.t.u.). The cal-
orie is the unit in the metric system and the standard calorie is the
heat required to raise i gram of water i C. at the point of its greatest
density (4 C.). It is, however, often stated more conveniently as
the heat required to raise one gram of water from 15 to 16 C. The
large calorie is. the same except that a kilogram of water is used in-
stead of a gram.

The standard British thermal unit (B.t.u.) which is generally
employed by English-speaking engineers is the heat required to raise
i pound of water from 39.1 F. to 40.1 F., this corresponding in the
English system to the point of greatest density of the water. In
recent years the unit is often described as the heat required to raise
i pound of water from 60 to 61 F., or from 62 to 63 F., as this is a
little more convenient and the latter figures are usually adopted in
practice. The difference in all these cases is very small.

To express calories as British thermal units, multiply the number
of calories by f or 1.8.

The calorific value is sometimes expressed as the real calorific value
and sometimes as the industrial calorific value. The real calorific
value is the result obtained when complete combustion occurs in the
laboratory in an apparatus such as the calorimeter and the industrial
calorific value is the value obtained when the coal is burned under a
boiler. The latter result approaches much more closely that which
is obtained in industrial operations and it is always lower, owing to
various losses, than the real value. It is measured as the heat neces-
sary to vaporize large quantities of water and the weight of the coal
used in some cases may be 1500 to 2000 kilograms.

1 Maumene, J., Compt. Rend., Vol. 55, p. 432, 1862.

72 CHEMICAL ANALYSIS OF COAL

The Bomb Calorimeter

The calorimeter in some form has been in use at least since the
time of Laplace and Lavoisier and it was practically perfected by
Berthelot and Vielle, but it was not until Mahler took up the work
for the Societe d'Encouragement a ITndustrie Nationale in France
that a satisfactory calorimeter for practical uses was designed. The
early calorimeters contained a great deal of platinum and this made

Fig. 12. Emerson fuel calorimeter with diagram of bomb and pressure
gauge and details of the ignition wiring.

them very expensive. The Mahler bomb calorimeter was so much
cheaper and so efficient that this general type, now known under
many modifications, is almost universally adopted. The calori-
meters which may be used for standard determinations are the Em-
erson, Atwater, Davis, Peters, Parr, Mahler and Williams or similar
types. One of the requirements is an inner surface of platinum, gold,
porcelain, enamel or other material which is not attacked by products
of combustion such as sulphuric and nitric acids.

DETERMINATION BY CALORIMETER 73

Determination by calorimeter. To determine the calorific value
by means of one of these calorimeters of the Mahler type, 1 place i
gram of 6o-mesh coal on an asbestos mat in the platinum tray. The
asbestos should be washed and ignited before using. The terminals
of the firing circuit are connected by about 13 mg. of fine iron wire
about 105 mm. long by 0.16 mm. in diameter. Platinum wire should
be used if the bomb is platinum-lined and care must be taken to see
that the terminals are clean. The wire is pressed down on the coal
and the tray placed in the bomb. The lid is screwed down tightly
on the lead gasket. Oxygen is forced into the bomb very slowly
until the pressure within the bomb reaches 1 8 to 20 atmospheres with
the needle-point valve closed just tight enough to avoid leakage.

The brass bucket is placed in the insulating jacket and the bomb,
full of oxygen, is placed in the brass bucket which contains about
2000 to 2500 c.c. of distilled water. The quantity of water used
varies with the type of calorimeter.

The stirring apparatus is adjusted so that it does not strike the
bomb or bucket. The thermometer, which is graduated to 0.01 C. or,
better, to 0.001 C., must not touch any metal parts and its bulb
should be about 5 cm. from the bottom of the bucket. The terminals
of the bomb are connected with wires leading to the switch. After
the stirrer has been in motion until the water is thoroughly mixed the
first reading of the thermometer is taken by means of a reading
telescope attached to a ca the tome ter. The stirring is continued
uniformly during the test and in a covered calorimeter trie temperature
should never be allowed to rise more than i C. above that of the
water jacket.

Taking readings: The time required for the determination may
be divided into the preliminary period, the combustion period and the
final period. In the preliminary period five readings are usually
taken one minute apart until the rate of change per minute is prac-
tically constant. After the fifth reading is taken a current of 75
volts is turned on for about one-half second thus starting the com-
bustion period. The first two readings in this period are taken one-
half minute apart because of the great change in ratio. The tem-
perature rises to a maximum and then begins to fall. The readings

1 Lord, N. W., and others. Analysis of coals. U. S. Bur. of Mines, Bull. 22, Part I,
p. 17, 1913. Also Stanton and Fieldner, Op. cit., p. 26.

CHEMICAL ANALYSIS OF COAL

are made regularly every minute after the first minute and the first
reading taken after the rate of fall becomes uniform is the last read-
ing of the combustion period. The readings are continued every
minute for five or six minutes composing the final period.

Calculation of the readings: The following plan shows the method
of calculating the calorimeter readings (weight of sample i.oooo
grams).

Time Readings
p. m. C.

23 . 874 o . 0058 rate of

i-54
55

.56
57

23.879

23-885
28.892

change per minute
in preliminary
period

. S 8(T) 23.897 + 0.00580

+ O.OO27 6

.585 24.160 + 0.00490

+ o.ooi4 6

59
.60

2.01
.02
03

25.430 + o.ooo8 a

- o.ooo6 6

26. 280 O.OO2O a

26.439 0.00250

26.463 0.0026
26.466 0.0026

- 0.00236
O.OO26 6

O.OO26 6

26.463
23.897

Observed temperature

change 2 . 566

Thermometer correction 002

(Supplied with thermometer)

2.564
Heat loss o . 0066

Water equivalent

Total heat developed in cal-

ories. . .
Correction

Heat developed by combus-
tion of sample in calories

7,670.4

.04 (t) 26.463

0.0026*

0.0066 algebraic sum.

.05 26.460

.06 26.458

.07 26.455 ~ 0.0026, rate of change in final period

.08 26.454

.09 26.450

Calories
= 17-9
= 12.5
9-9

Wire burned = 11.2 mg

Titer (i c.c. = 5 cal.) 2.5 c.c

Sulphur (o.oi g. or i per cent = 13 cal.) 0.76 per cent

Room temperature = 24 C.

a Computed rate per minute of temperature change at each reading: b Temperature
correction for heat loss during each interval.

DETERMINATION BY CALORIMETER 75

Let A equal the rate of change during the preliminary period and
B equal the rate of change during the final period, then A-B will equal
the change in rate during the combustion period.

Let T equal the initial temperature of the combustion period and
/ the final temperature of the combustion period, then T-t equals
the apparent change in temperature during the combustion period.

Then - - = the change in rate per degree of temperature change
J. /

during the combustion period.

If the temperature readings during the combustion period be
represented by t\, /2, ^3, etc., or in a general way by /, then the com-
puted rate per minute of temperature change at each reading is
found by the following formula:

To obtain the temperature correction for heat loss during each
interval multiply the mean of the computed rate per minute of tem-
perature change, for any two readings, by the interval in minutes.
The algebraic sum of these corrections gives the total correction for
heat loss (e. g. 0.0066 C.). This quantity is added to the ob-
served temperature change, and this sum multiplied by the weight
of the water plus the water equivalent of the apparatus gives the
total heat developed.

Corrections for various factors: The observed temperature should
be corrected for errors in the thermometer. The correction for the
combustion of the iron wire is 1.6 calories per milligram. The cor-
rection for sulphur burned to sulphuric acid is 1.3 calories per milli-
gram. The correction for nitrogen to aqueous nitric acid is made
by titrating the bomb liquor with standard ammonia solution (0.00587
grams NH 3 per cubic centimeter). This solution is equivalent to 5
calories per cubic centimeter.

Analysis of the calorimeter washings: The calorimeter is thor-
oughly rinsed out after the combustion test is finished and the wash-
ings are titrated with standard ammonia solution (0.00587 gram per
cubic centimeter) to make the acid correction. Methyl orange is
used as an indicator. The nitric acid which is present is developed
from the nitrogen in the coal and from the air imprisoned in the
bomb. The solution also derives some acidity from the sulphur in

76 CHEMICAL ANALYSIS OF COAL

the coal. The sulphur is readily precipitated by barium chloride
(BaCl 2 ) as in the Eschka method already described. Instead of the
ammonia solution some analysts much prefer Stohman's solution,
in which sodium carbonate (Na 2 CO 3 ) is used, because of the greater
regularity of the results obtained with it. One cubic centimeter of
this solution contains 0.003706 gram sodium carbonate and it is
equivalent to 0.004406 gram nitric acid. One calorie of heat is
produced when this acid is formed. Methyl orange is used as indic-
ator.

It is convenient to make the ammonia solution used of such strength
that i c.c. is equivalent to 0.00483 gram of nitrogen because this
weight of nitrogen burned to nitrogen pentoxide (N 2 O 5 ), plus water
generates 5 calories of heat.

When nitrogen burns to N 2 O 5 -f water 1035 calories of heat per
gram are produced.

The ammonia solution is made up according to the following equa-
tion:

HNO 3 + NH 3 = NH 4 NO 3 .
Since N = 14 and NH 3 = 17,

14 : 17 = 0.00483 gram : 00587 gram.

Therefore 0.00587 gram NH 3 is equivalent to 0.00483 gram of nitro-
gen which when burned to nitric acid generates 5 calories of heat.
The standard solution contains 5.87 grams of NH 3 per liter.

The ammonia used must also neutralize the sulphuric acid gener-
ated in the bomb from the sulphur and the strength of the ammonia
solution in terms of the sulphur in the form of sulphuric acid is de-
termined by the following equation:

2NH 3 + H 2 S0 4 = (NH 4 ) 2 S0 4

2NH 3 : S = 34 : 32 = 0.00587 gram NH 3 : 0.0055 gram S.
The heat of combustion of the sulphur when converted into aqueous
sulphuric acid is 4450 calories per gram of sulphur provided it is
burned in oxygen at high pressure, as it is in the bomb. Since the
heat of combustion of the sulphur burned under a boiler in industrial
operations where it only changes to sulphur dioxide (SO 2 ), is reck-
oned as 2250 calories per gram of sulphur, a correction must be made,
and the figure employed is 2200, or the difference between the above
figures. Now, since i c.c. of the ammonia solution is equivalent to
0.0055 gram of sulphur, 0.0055 X 2200 = 12.1 calories. This is the

DETERMINATION BY CALORIMETER 77

heat correction to be made on the basis that all the acidity in the
washings from the bomb is due to the presence of sulphuric acid.
A correction, however, must be made for the nitric acid as outlined
above. The difference 12.1 5 = 7.1 calories, and 7.1 -5- 0.0055
= 1291 calories per gram of sulphur, or practically 13 calories for
each per cent of sulphur present.

Standardization of the calorimeter: A number of methods have
been suggested for the determination of the water-equivalent of the
calorimeter. One method makes use of the specific heats of the
various portions of the apparatus. Another is the electric method,
another the mixing of portions of water having different temperatures, 1
and still another the employment of different quantities of water
while generating the same amount of heat in the bomb. None of
these when considered from all points of view are as satisfactory for
commercial operations as the method where substances of known
calorific values are used. The calorific value of these substances is
determined with elaborate electric apparatus by the Bureau of Stand-
ards and samples may readily be obtained. The substances mostly
used are benzoic acid, naphthalene, and sucrose. A weighed portion
of one of these substances is placed in the bomb and the experiment
carried out just as for a sample of coal. The weight of the sample
should be such that its calorific value will be as nearly as possible
that of a gram of coal.

Method of calculating the relations between "air-dried" "as received"
"moisture-free" and "ash-free" samples: The following system is
adopted in calculating percentages in the "air-dried" sample to those
in the "as received" sample:

1 Bownocker, J. A., Lord, N. W., and Somermeier, E. E., Coals of Ohio. Ohio State
Geol. Survey, Bull. 9, p. 331, 1908.

CHEMICAL ANALYSIS OF COAL

"Air-dried" condition

"As received" condition
ioo air-drying loss

Moisture at 105 ^. multiplied oy

Volatile matter
Fixed carbon
Ash
Sulphur " "
Hydrogen

Carbon " "
Nitrogen " "
Oxygen "

Calorific value " "

Calculating percentages in the
1 ' moisture-free ' ' sample .

"Air-dried" condition
Volatile matter multiplied by

Fixed carbon
Ash

IOO

air-drying loss = moisture
ioo air-drying loss i_*:i.._

ioo - air-drying loss

IOO

ioo air-drying loss

IOO

ioo - air-drying loss

IOO

ioo air-drying loss ,

IOO

air-drying loss _ ,

9
ioo - air-drying loss _

IOO

ioo - air-drying loss _ h

IOO

ioo air-drying loss ,

1
8 (air-drying loss)

9
ioo air-drying loss , .- ,

" air-dried" sample to those in the

"Moisture-free" condition
^~ volatile matter

ioo moisture

IOO

ioo moisture
ash

ioo moisture

ioo moisture
hydrogen

Hydrogen ( 9 moisture)
Carbon

ioo moisture

IOO

, . _ , rrr carbon

ioo moisture

IOO

ioo moisture

IOO

' oxygen

Uxygen ^ -- moisture,;
Calorific value " *

ioo moisture

(i calorie =1.8 B.t.u.)

CALCULATION OF THE CALORIFIC VALUE OF COAL 79

To calculate the analyses to an "ash-free" and " moisture-free"
basis use as denominator 100 (moisture + ash) instead of " 100
moisture." ~~

Calculation of the Calorific Value of Coal from the Analysis

The formula of Dulong is recognized as the most satisfactory for-
mula so far devised for determining the calorific value from the an-
alysis. It has, however, been modified in a number of ways. It
is usually expressed as: Calorific value in calories per gram = 8080

C -f- 34,460 ( H J + S 2250, where C, H, O, and S, respectively,

indicate the weights of the carbon, hydrogen, oxygen, and sulphur.
This formula is not quite correct in view of the figures 1 lately ob-
tained for the heating value of carbon, which should be approximately
8100 C instead of 8080 C, and 34,500 is a better figure to employ than
34,460.

To avoid the necessity of analyzing the coal for hydrogen Parr 2
uses the formula 8080 C + 34,500 "H" + 2250 S in which "H" rep-
resents the available hydrogen in the coal, or hydrogen not combined
with oxygen to form water, and it is derived from a curve which is
based on the principle that the hydrogen is united with some of the
volatile carbon. He considers that the value for hydrogen so de-
rived and used in Dulong's formula will produce results practically as
satisfactory as those obtained from the original formula, and they
are obtained much more readily.

The calorific value from the proximate analysis: If the calorific
value could be calculated from the proximate analysis a great advance
would be made over Dulong's formula. What appears to be a sat-
isfactory method for computing the calorific value of certain coals
from the proximate analysis, has been suggested by Goutal 3 as a
result of experiments on over 600 specimens of various kinds of coal.
He used the following formula:

P = 82 C + a V in which

P = the number of calories in a gram of fuel,

C = the percentage weight of fixed carbon, and

1 Richards, Metallurgical calculations, Part I.

2 Parr, S. W., Op. cit, p. 64.

3 Goutal, M., Sur le pouvoir calorifique de la houille. Compt. Rend., Vol. 135, p.
477, 1902

CHEMICAL ANALYSIS OF COAL

V = the percentage weight of the volatile matter; while

a = a coefficient which varies with the percentage of volatile

matter, V, in the pure coal.
a is found from a curve (Fig. 13). This curve is constructed by

145

140

135
110

(

125
120
115
110
105
100
95
90
85

--*.

-*^.

5 10 15 20 25 30 35

Fig. 13. Goutal's curve for the determination of the calorific value of coal
from the proximate analysis.

taking the values for V as the abscissae and the values for a as the
ordinates. V is found from the formula

and a was found as a result of a vast number of analyses which were
made during this investigation. In the anthracites a = 100, a con-
stant.

The values 5, 10, 15, 20, 25, 30, 35, 38, and 40 per cent for volatile
matter in the pure fuel (V) give the corresponding figures for a as
follows: 145, 130, 117, 109, 103, 98, 94, 85, and 80 per cent respec-
tively.

For coals with a value for V between 5 and 35 per cent the variation
between the results given by this method and those given by the
calorimeter rarely vary more than i per cent. The value may reach
2 per cent in some anthracites and in weathered coals or lignites, and
for these the calorimeter method is the only accurate means of de-
termining their calorific value.

The following table from Carnot shows how closely the results
obtained by Goutal's formula correspond to those obtained from
Dulong's formula and the calorimeter. They are in every case closer
to the calorimetric figures than are those from Dulong's formula.

CALCULATION OF THE CALORIFIC VALUE OF COAL

CALORIFIC

VALUE BY VARI

ous MEANS

Fixed
carbon

Volatile
matter

Calorimetef

From Du-
long's for-
mula

FromGoutal's
formula

Anthracite of Pennsyl-
vania

Q7 .O

3 .0

8256

8462

8380

Anthracite coal of
Keboa

Q4. 8

8<?32

8<>28

8<2Q

Anthracite coal of Creu-
sot

8q 6

IO 4.

8687

8704

8680

Semi-fat coal of Angers
Fat coal of Porter

85-9
80.7

I4.I
19.3

8656
8667

8750
8382

8722
8740

Fat coal of Ronchamp. .
Gas coal of Bethune
Gas coal of Montram-
bert

76.8
69.6

6s 7

23.2
30-4

2 A *}

8797

8668
8^08

8678
8654

8-1O7

8702
8671

86l2

CHAPTER IV
VARIETIES AND RANKS OF COAL

Introduction

The various classifications of coal which have been suggested are
discussed in another chapter. There are, however, certain varieties
recognized almost universally in science and commerce which should
be described in detail before a comprehensive description of the less
familiar classifications can be given. These varieties are not sharply
separated and they grade into one another, so that in describing
them the proportions of their constituents must be stated as varying
within wide limits. Two coals with a certain percentage of fixed
carbon may have very different calorific properties owing to the fact
that the moisture or the ash may vary considerably, and consequently
if one constituent be chosen as a standard the others do not necessarily
agree. An attempt has been made, therefore, to give the limits of
variation as well as the average properties of these different varieties
as they have been recognized by many writers from numerous coun-
tries. The ideal manner of presenting all the constituents other than
moisture and ash, would be on a "moisture-free" and " ash-free"
basis, but since the analyses selected have not been so recorded they
have not been computed on this basis in the following figures unless
it be so stated in the text.

Since it is so generally admitted that all coal has been derived from
peat in some form and that it has arrived at its present state as the
result of various geological processes, peat is briefly described with
the varieties of coal. It is not regarded as a variety of coal, but
rather as an incipient stage in the formation of that substance.

Peat (Fr. Tourbe, Ger. Torf). Peat is an accumulation of
vegetal matter which has suffered varying degrees of disintegration
and decomposition, and it contains a high percentage of water and
oxygen. It varies in physical character from a distinctly fibrous and
woody, light-brown material to a dark-brown and black jelly-like
substance. There are all gradations from peat to muck in which

PEAT 83

mineral matter becomes so abundant as to prevent its free burning.
Although it may be cut from the bog in blocks peat is seldom suffi-
ciently compact to make a good fuel without compressing.

The composition of peat is illustrated by the following figures.
Water in original samples from different parts of the bog is 62.98 to
90.12 per cent, usually 80 to 90 per cent. In a large number of
analyses of dried specimens from various countries the following
variations and averages in composition are shown:

Variations

Carbon 37 . 15-66 . 55 per cent

Hydrogen 4 . 08-10 . 39 "

Oxygen 18. 59-42 .63 "

Nitrogen o . 77- 3 . 10 "

Fixed carbon 10.39-33 .91 "

Volatile matter 43 .38-73 .60 "

Ash 1.05-32.95 "

Average
52.83 per cent

5-97 "
33-12

1-34 "
23-59 "
60. 18 "

9.58 "

Sulphur is often as low as one-tenth of i per cent and it is usually
below i per cent, but it may rise higher in pyritiferous types. The
calorific value varies from 5500 to 10,000 B.t.u. in air-dried samples.

Fig. 14. Branch of tree altered to lignite but preserving the original
markings. From the coast of Alaska. (Collected by W. R. Crane.)

Dopplerite: This is a variety of peat, found chiefly in Styria but
also occurring elsewhere in Europe, whose composition shows it to
be highly acid. An analysis by Schrotter shows that it contains

Carbon 48 . 06 per cent

Hydrogen 4-98 "

Oxygen 40 . 07 "

Nitrogen i . 03 "

Ash 5.86 "

It is amorphous and in the fresh state is elastic like rubber. Its

84 VARIETIES AND RANKS OF COAL

luster is greasy and its specific gravity is 1.089. It burns with little
or no flame and emits an odor like peat.

Lignite and brown coal (Fr. Lignite, Ger. Braunkohle). There
seems to be no definite record of the first use of the term lignite.
It is a French word and may possibly have arisen from the term
Lithanthrax ligneus which, according to Hausmann 1 was used by
Wallerius 2 for the distinctly woody type of brown coal. It was
used by Brongniart 3 as early as 1807 and it is generally found in all
French works since that time. The German word, Braunkohle was
used in different ways by Karst, 4 Neuss, 5 and Blumenbach 6 about
the beginning of the nineteenth century.

In America the terms lignite and brown coal have come to be used
interchangeably because both the amorphous and the xyloid, or
woody types may be brown in color and may have similar chemical
properties and uses. The two types grade into each other so that no
sharp distinction can be made between them. In recent years, how-
ever, the United States Geological Survey has decided to adopt the
term subbituminous coal for the compact, so-called "black lignite"
and to restrict the term lignite to the lower grade brown coal which is
usually, but not always more or less woody and on drying splits up
into slabs. 7 (Plate III, Fig. i.) The distinction is thus made on
the basis of color. The composition of lignite or brown coal, as these
terms are used in various countries, is indicated by the following
figures compiled from numerous analyses of this coal from almost
all parts of the world :

Variation Average

Moisture o . 75-43 . oo per cent 14.42 per cent

Volatile matter 27 . 00-53 " 4 7^ "

Fixed carbon 16 . 00-51 .00 " 36 . 37

Ash 2.60-42.00 ' 9.32

Sulphur 0.16-9.00 " i .14 "

Hydrogen . 5 . 14 "

Carbon 58.14 "

Nitrogen i . 05 "

Oxygen 25 . 17 "

Hausmann, J. F. Ludw., Handbuch der Mineralogie, Vol. i, p. 79, 1813.
Wallerius, J. G., Systema Mineralogicum, Vol. 2, p. 98, 1775.
Brongniart, Alexandre, Traite 61ementaire de Mineralogie, Tome 2, 1807.
Karst, Mineralogische Tabellen 58, 1800.
Neuss, Min. II, 3, 154.

Blumenbach, Handbuch Der Naturgeschichte I, 660.

Campbell, M. R., A practical classification of low-grade coals. Econ. Geology, Vol.
3, p. 134, 1908.

PLATE III.

Fig. i. North Dakota lignite showing characteristic fracture and xyloid

texture.

Fig. 2. Bituminous coal showing characteristic cubical fracture. 85

86 VARIETIES AND RANKS OF COAL

The calorific value of lignite, undried as received from the mine,
is 5500-7000 B.t.u. moisture-and-ash-free, 10,000-12,000 B.t.u.
The specific gravity is 0.5 to 1.30. It colors brown a solution of
potash. Some lignites in France are so high in pyrite that they can
be used in the manufacture of iron sulphate and alum, and certain
earthy varieties, known as terre d'ombre or ombre de Cologne, 1 are used
for coloring matter.

Dysodile (Houille, or lignite papyracee): This is a laminated lig-
nite high in siliceous ash. The color is a yellow to greenish-gray, the
specific gravity 1.14 to 1.25. It burns readily with a bright flame
and gives off an odor like asafetida. The ash has been found to con-
tain abundant shells of diatoms. An analysis by Church 2 shows
the following composition, ash free:

Sulphur 2.35 per cent

Hydrogen 10 . 04 "

Carbon 69 . 01 "

Nitrogen i . 70 "

Oxygen 16 . 90 "

It occurs in Tertiary formations, and is found in limestone in Sicily
and in lignite in Germany and the Central Plateau of France.

Subbituminous coal. This term has been officially adopted by
the United States Geological Survey to include the glossy black coal
which grades downward in properties from bituminous to lignite but
which, as a rule, is of a considerably higher grade than the woody or
ligneous type. It includes the black lignite and since it may be lig-
neous in texture it can in some cases be distinguished from brown coal
in the field only by its black color, while it is separated from bituminous
coal above by its mode of weathering. According to Campbell. 3
it parts along a surface nearly parallel to the bedding and thus breaks
up into thin slabs, or it checks irregularly and does not disintegrate
into cubes after the manner of bituminous coal. (Plate IV, Fig. i.)
The fracture is sometimes conchoidal. It often has a distinctly
pitchy luster and is therefore sometimes called Pechkohle (pitch coal)
by the Germans. Analyses of samples of this variety of coal as it is

1 Moissan, Traite" de chimie min^rale, Vol. 2, p. 356, 1905.

2 Church, A. H., Dysodile. Chem. News, Vol. 34, p. 155, 1876.

3 Op. cit.

BITUMINOUS COAL 87

known in the United States show the following variations in per-
centage composition, 1

Moisture i 94~4Q . 58 per cent

Volatile matter 7 50-70.86 "

Fixed carbon 18 . 00-83 o "

Ash 2.06-55.40 "

Sulphur 0.15-8.65 "

Hydrogen i . 76- 6 . 98

Carbon 30.68^86.85

Nitrogen o . 49- 2.13

Oxygen 2 . 80-52 . 18

Air-drying loss o . 80-28 . oo

Calorific value 6205-14,843 B.t.u.

Good grades of this coal have a calorific value of 8000 to 10,000 B.t.u.

Bituminous coal (Fr. Houille, 2 Ger. Schwarzkohle 3 ). The term
bituminous has evidently been handed down from the earliest writers
on mineralogy because they frequently spoke of the volatile ma-
terials given off this type of coal on distillation, as bitumen. Wal-
lerius called this coal Bitumen lapideum. Among some modern
writers there is a tendency to discard bituminous for the term humic
since the coal lacks true bitumen in important amounts and contains
a large percentage of humic acid.

Bituminous coal burns with a long yellowish flame and gives off
a suffocating bituminous odor. It is more or less laminated as a rule,
and the luster of the different layers varies greatly. It may be resin-
ous, silky, pitchy, or dull and earthy. It soils the fingers when
handled. The color varies from pitch-black to dark gray. The
fracture may be irregular and somewhat splintery but it is almost
always roughly cubical. (Plate III, Fig. 2.) It is, as a rule,
conchoidal in cannel coal.

There are several types of bituminous coal. These include Caking
and Non-caking coal the latter including the Cherry and Splint
coals of England, Cannel coal and its related types, Torbanite and
Boghead.

Caking or coking coal: This coal has the property of softening and
running together into a pasty mass at the point of incipient decom-

1 Lord, N. W., and others, Analyses of coals in the United States. U. S. Bur. Mines,
Bull. 22, 1912.

2 De Lisle, Vol. 2, p. 590, 1783. Hauy, Trait< de mineralogie, Vol. 3, p. 316, 1801.
8 Hausmann, Op. cit., p. 73.

88 VARIETIES AND RANKS OF COAL

position and then at higher temperatures giving off its volatile con-
stituents as bubbles of gas. There remains a hard, gray, cellular
mass called coke (Fr. Coke, Ger. Coaks). While there is no chemical
or simple physical test which will distinguish coking coals in all cases,
there are some tests which will usually indicate their coking proper-
ties. White 1 states that practically all coals with H : O ratios of 59
per cent or over seem to possess the quality of fusion and swelling
necessary to good coking. Most with ratios down to 55 will make
coke of some kind, while a few with ratios as low as 50 coke in the
beehive oven, though very rarely producing a good article. Coals
changing to anthracite, the weathered coals, and the coals of the
boghead cannel group show considerable variation from this rule.
It has been shown, also, that the solubility of coal in aniline may be
used as an indication of coking properites. Vignon 2 says that the
coke given by the coal insoluble in aniline is powdery and that of
the coal soluble in aniline is agglomerated and swollen.

A simple and, in many cases, a satisfactory test is that known as
the agate mortar test. Coals which coke, when rubbed with a pestle
in an agate mortar, cling to the sides of the mortar while the non-
coking coals do not. 3

Non-caking or non-coking coal: This coal may resemble the coking
coal in all outward appearances but in composition it differs in the
ratio of the hydrogen to the oxygen and it does not cling to the sides
of an agate mortar when rubbed with the pestle. It burns freely
without softening and it leaves a powdery mass instead of a strong
cellular mass. The Cherry coal, so well known in England, is a
variety of the non-coking coal. It received its name because of its
fine luster. It is usually velvet-black in color, is brittle and crumbles
rather readily. Splint coal or, as it is sometimes called, "Slate
coal," is also an English name for a variety of non-coking coal. It is
black and as a rule it has a resinous and glistening luster, but often
it is dull and contrasts with the brilliant luster of the Cherry coal.
It fractures in two directions, the longitudinal break being curved
and slaty and the transverse uneven and splintery.

1 White, David, The effect of oxygen in coal. U. S. Geol. Survey, Bull. 382, 1909.

2 Vignon, Leo, Sur les dissolvants de la houille. Compt. Rend., Tome 158, pp. 1421-
1424, 1914.

3 Pishel, M. A., A practical test for coking coals. Econ. Geology, Vol. 3, pp. 265-275,
1908.

CANNEL COAL 89

The composition of bituminous coal, as it has been recognized by
different writers in various countries is as follows:

Variation Average

Moisture 0.04-34.33 per cent 2 . 50 per cent

Volatile matter 8.63-64.31 " 32.00 "

Fixed carbon 26.49-80.60 55.00

Ash 0.28-45.00 " 10.00 "

Sulphur 0.0012-10.5 " 0.80 "

Hydrogen 1.00-8.80 " 4.80 "

Carbon 44.00-85.30 " 74.00 "

Nitrogen 1.00-9.20 " 1.30 "

Oxygen 0.95-46.90 " 7.00 "

Calorific value 6840-15,169 B.t.u. 13,200 B.t.u.

The specific gravity varies from 1.15 to 1.5, with an average of 1.3.
A good average for the percentage composition and calorific value of
the bituminous coals collected in the United States between the
years 1904 and 19 lo 1 is as follows:

Moisture 2 .00-10.00 per cent

Volatile matter 25 .00-40.00 "

Fixed carbon 45 . 00-65 "

Ash 5.00-12.00 "

Sulphur 0.50- 2.00 "

Hydrogen 4 . 50- 6 . oo "

Carbon 60. 00-80. oo "

Nitrogen o. 80- 2 . oo "

Oxygen 7 . 00-20 . oo "

Calorific value 12,000-14,500 B.t.u.

Cannel coal. 2 This coal was originally known as candle coal, but
the term cannel was employed by the earliest mineralogists. Kirwin 3
describes this coal, along with Kilkenny coal, as dull black in color
and with conchoidal fracture when broken transversely. It burns
with a bright lively flame and in some cases it may be kindled by the
application of a match owing to the large percentage of highly volatile
constituents which it contains. This property gave rise to the name
candle coal. A variety of Scotch cannel which produces a marked
crackling sound has been called parrot coal and Dana 4 mentions a
variety from South Wales known as horn coal because, on burning,
it emits an odor as of burning horn.

1 U. S. Bur. of Mines, Bull. 22.

2 Ashley, G. H., Cannel coal in the United States, U. S. Geol. Survey, Bull. 659, 1917.

3 Kirwin, Richard, Elements of mineralogy. P. 215, 1784.

4 Dana, E. S., A system of mineralogy. 6th ed., p. 1022, 1895.

VARIETIES AND RANKS OF COAL

Cannel coal is generally described as a non-coking bituminous
type, but it is just within the boundary of a special group, the mem-
bers of which are char-
acterized by a higher
percentage of volatile
oils and gases than that
found in ordinary bitu-
minous coal. To this
group Rogers applied
the term hydrogenous
or gas coals, 1 while Po-
tonie 2 considers most
of them as sapropelic
types. Cannel un-
doubtedly consists
chiefly of the spores of
plants or canneloid
and, as a result, differs
FIG. 15. Photomicrograph of section of cannel markedly from ordin-

coal consisting almost entirely of flattened spores. coal in the char

(Photo by E. C. Jeffrey.) "

acter of the materials

which compose it. (Fig. 15.) Beginning, therefore, with a different
type of vegetal matter it is possible to have it pass through the
stages corresponding to brown and to bituminous coal, still retaining
its canneloid character. Its average composition is illustrated by
the following analysis of Kentucky cannel:

Moisture 2.36 per cent

Volatile matter 48 . 40

Fixed carbon 38 . 75

Ash 10. 49

Sulphur i . 20

Hydrogen 6 . 47

Carbon 71-98

Nitrogen i . 16

Oxygen 8 . 70

Calorific value i3>77 B -t.u.

The specific gravity varies from 1.2 to 1.3.

1 Rogers, H. D., Geology of Pennsylvania. Vol. 2, p. 990, 1883.

2 Potoni6, H. ; Die Enstehung der Steinkohle und der Kaustobiolith iiberhaupt, wie
des Torfes, der Baunkohle, des Petroleums, u.s.w., 5th ed. 1910.

CANNEL COAL 91

Torbanite: This is a variety of the boghead coals and it is named
from Torbane Hill in Scotland where it has been mined for many
years. It differs so much from ordinary coal that a prominent law-
suit was carried through the Scottish courts about the middle of the
last century to determine whether the mining of the rock was governed
by the laws controlling mineral or coal deposits. The trial was
settled in favor of the latter. Like the other bogheads it is charac-
terized by a very high percentage of volatile constituents including
illuminating and lubricating oils, paraffin, and large quantities of
illuminating gases, running from 14,000 to 18,000 cubic feet per ton.
There is a difference of opinion concerning its origin, some regarding
it as derived from spores, others from algae, and it is often described
as a variety of cannel coal. The evidence is strongly in favor of the
origin from spores rather than from algae. It is closely related to the
kerosene shales and bituminous schists. Its color is dark brown, its
surface dull and lusterless. The fracture is irregular to subcon-
choidal. According to Dana 1 the hardness is 2.25 and the specific
gravity 1.17 to 1.2. Analyses quoted by the same authority show
that the composition is approximately as follows, with ash excluded:

Hydrogen n .48 per cent

Carbon 81.15 "

Nitrogen 1.37 ;<

Oxygen 6 . oo '

The ash runs about 20 per cent. It is much higher in hydrogen than
any ordinary type of coal.

Byerite: This is a term applied by Mallett 2 to a so-called mineral
coal, somewhat resembling Torbanite but differing from it in not
crackling in the fire, in being heavier specific gravity 1.323 and
in melting and intumescing when heated. It gives a large amount
of gas and tarry oils, about 30 per cent more than English cannel.
An analysis gave the following results moisture 6.02 per cent;
volatile matter (gas and tarry oils) 39.95 per cent; fixed residue,
consisting of coke and ash 54.03 per cent. The coke is a true coke
but resembles the residue from the distillation of sugar and is too
porous and crumbling to support a furnace burden. It is jet-black
in color but gives a brown powder which does not color a potash solu-
tion brown. It is insoluble in carbon bisulphide, ether, or turpentine.

1 Op. cit., p. 1022.

2 Mallett, E. J., On Middle Park mineral coal. Am. Jour, of Sci., Vol. 9, p. 146, 1875.

92 VARIETIES AND RANKS OF COAL

Semibituminous coal. H. D. Rogers 1 adopted this term for coal
containing from n to 18 per cent volatile matter and to include what
has been called dry bituminous coal, as opposed to the group of fat
coals including caking coal, cherry coal, and splint coal. This type is,
caking and, non-caking. In spite of the fact that on heating it softens
and swells into a coke, this coke does not always agglutinate or cohere.
Although the term is quite widely used in the United States, it seems
a little unfortunate in view of the fact that the prefix semi conveys the
idea that it should be a little below bituminous coal in the ascending
scale from peat to anthracite, and it does not harmonize with the use
of the term semianthracite. The term superbituminous might have
been suggested as a more appropriate one. Rogers did not give any
detailed description of this type of coal but various analyses from
fields throughout the United States 2 show the varying proportions
of the following constituents and their average in a good quality of
this variety of coal:

Variation Average

Moisture o . 78- 8 . 99 per cent 2 . oo- 4 . oo per cent

Volatile matter 7 . 40-23 .84 14 . 00-18 . oo "

Fixed carbon 57. 11-80.89 70.00-80.00 "

Ash 1.80-34.15 4.00-8.00 "

Sulphur o . 44- 6 . 47 o . 50- i . 20 "

Hydrogen 3 .34-5.17 4.00-5.00 "

Carbon 51.23-85.54 76.00-82.00 "

Nitrogen 0.81-1.82 1.00-1.50 "

Oxygen 3.38-13.70 4.50-6.50

Calorific value 8386-14,814 B.t.u. 14,000-15,000 B.t.u.

Semianthracite. This name was adopted by Rogers 3 at the same
time as the term semibituminous, to cover the coal between
semibituminous and anthracite. He describes it as possessing
to a lesser degree the properties characteristic of anthracite. The
conchoidal fracture is not so well developed as in anthracite, and the
cleats are more numerous. It crumbles more readily in the fire and
owing to a greater percentage of volatile matter it kindles more
readily than anthracite and emits a small amount of yellow flame
when ignited. Owing to more rapid consumption its efficiency is
greater than that of anthracite for certain purposes. The volatile

1 Rogers, H. D., Geology of Pennsylvania, pp. 988-990, 1858.

2 Analyses of coals in the United States. Bur. of Mines, Bull. 22, 1912.

3 Op. cit.

PLATE IV.

FIG. i. Subbituminous coal showing irregular fracture.

FIG. 2. Pennsylvania anthracite showing typical conchoidal fracture.

(9-0

94 VARIETIES AND RANKS OF COAL

matter varies from 6 to 1 1 per cent and averages from 7 to 8 per cent.
The specific gravity is about 1.4. Analyses of this type of coal from
the United States 1 indicate the following range in composition:

Moisture i . 96- 7 . 94 per cent

Volatile matter 6.81-32 .46

Fixed carbon 58 . 24-82 . oo

Asn 4.33-14.50

Sulphur 0.57- 4 . 05

Hydrogen 3.69- 4.81

Carbon 72 . 43-80 . oo

Nitrogen 0.51- 1.45

Oxygen 5 . 46-10 . 02

Calorific value 12,460-14,184 B.t.u.

A proximate analysis of a good grade of this coal is represented by the
following :

Moisture i . 94 per cent

Volatile matter 9 . 95 "

Fixed carbon 79 . oo "

Ash 8.80 "

Sulphur o . 29 "

Anthracite (Fr. Anthracite, Ger. Glanzkohle) . The first use of
this term among mineralogists is ascribed to Hauy, 2 although An-
thrazit may have been employed by Karst 3 ten years earlier. In
America this coal is frequently known as hard coal, and in Wales as culm
or stone coal. It is characterized by an iron-black color, and dull to
brilliant, and even submetallic luster. It does not soil the fingers as
bituminous coal does. It burns with a short, pale blue flame, emits
little odor, and does not coke. It commonly breaks with conchoidal
fracture and thus differs from bituminous coal which usually breaks
into roughly rectangular fragments (Plate IV, Fig. 2). When very
small fractures are numerous, the freshly broken surface shows
small rounded or oval, eyelike forms and it has then been called
"Bird's-eye" coal.

The calorific value of anthracite is not as great as that of semi-
bituminous or high grade bituminous coal because it does not develop
a high temperature so rapidly. This is owing to the small amount of
readily combustible material compared with the fixed carbon. It is

1 Analyses of coals in the United States. Bur. of Mines, Bull. 22, 1912.

2 Trait6 de mineralogie, Tome III, p. 307, 1807.

3 Op. cit.

ANTHRACITE 95

much sought after for domestic use on account of its lack of soot and
dust and because of the fact that it burns so much longer than other
types of coal.

Anthracite reaches the maximum hardness in coal. It varies from
2 to 2.5 in Moh's scale. Certain varieties of this coal are capable
of being cut and polished for ornamental purposes and some of that
from the Hazleton and Summit Hill districts of Pennsylvania is
used for this purpose.

Like that of all other coals, the composition of anthracite as it has
been mined in different regions varies greatly. The following figures
show the variation in the analyses from various sources.

Moisture o . 42- 5 . 61 per cent

Volatile matter i . 72-10. 75 "

Fixed carbon 73 . 71-90 . 90 "

Ash 3.20-30.09 "

Sulphur o . 17- 2 . 60 "

Hydrogen i . 89- 5.61 "

Carbon 78.41-83.89 "

Nitrogen 0.63- i .57 "

Oxygen 3 . 80-11 . 54 "

Calorific value 9230-13,298 B.t.u.

The specific gravity varies from 1.27 to 1.7.

The anthracite from Rhode Island is not included in the above list.
There the coal is in places graphitic, the moisture in the mine sample
runs as high as 23 per cent and the fixed carbon as low as 49 per cent
because of very high ash, although the volatile matter is as low as
2.5 per cent. The ash may be over 30 per cent and the oxygen is
high except in the dried samples. The nitrogen is usually below 0.5
per cent. The pecific gravity of the Rhode Island anthracite varies
from 1.43 to 2.2 1

The following averages represent the percentage composition of
good anthracite calculated on a moisture-free and ash-free basis:

Volatile matter i . 50- 6 . 50 per cent

Fixed carbon 93 . 00-98 . oo "

Sulphur o. 50- i . 50 "

Hydrogen i . 75- 4 . oo "

Carbon 90.00-94.00 "

Nitrogen 0.60- i . 25 "

Oxygen 1.25-2.75 "

Calorific value 14,500-15,000 B.t.u.

1 Ashley, G. H., Rhode Island coal. U. S. Geol. Survey, Bull. 615, 1915

9 6

VARIETIES AND RANKS OF COAL

The moisture will run from 2.5 to 4 per cent and the ash from 1.5
to 10 per cent.

The specific gravity of Pennsylvania anthracite varies from 1.42
to i. 65,* and of the Welsh anthracite from 1.29 to 1.45, averaging
about 1.33.

COMPARATIVE COMPOSITION OF WOOD. PEAT, AND COALS

Table showing the relative percentage composition of wood, peat, and coals.

Proximate analyses

Ultimate analyses

Calorific value

Kind of Fuel

i Cc/i

rt -jg

S
"a

<5 o

Wood

6.25

49.50

.10

43.15

5,800

Peat a

56.70

26.14

11.17

5-99

0.64

8.33

21.03

.10

62.91

53.40

1,992

3,586

Do c

60.37

25.80

13-83

.48

4.69

48.57

28.89

4,600

8,280

Lignite a

34-55

35.34

22.91

7 20

.10

6.60

42.40

42.13

15.50

3,939

7,090

Do ft

60.67

39-33

.89

4 74

72.79

19.60

6,762

12,172

Subbituminous a . .

24.28

27.63

44-84

3 25

.36

6.14

55-28

.07

33 90

16.20

5,209

9,376

Do b

38.12

61.88

4- 74

76.28

17 01

7,188

_ o

Bituminous a

3-24

27.13

62.52

7-H

5.24

78.00

7.47

i. so

7,733

13,919

Do b

30.26

69.74

.06

S-39

87.00

5.18

8,626

15,527

Cannel a

I 70

50.76

9-31

6.83

73-25

8.28

o. 40

14,251

Do b

J. . /U

42.96

7.46

82.31

7.61

8,896

16,013

Semibituminous a .

2.03

14.47

75-31

8.19

.26

4.14

79-97

.26

4.18

1.40

7,823

14,081

Dob

16.12

83.88

4-37

89.07

-40

2.64

8,713

15,683

Semianthracite a . .

3.38

8.47

76.65

11.50

.63

3.58

78.43

.00

4.86

2.60

7,309

13,156

Dob

9-95

90-05

3.76

92.15

.18

2.17

8,587

15.457

Anthracite a

2.80

1.16

88.21

7-83

1.89

84.36

.'63

4.40

i 50

7,388

13,298

Do b

1.29

98.71

.00

1.77

94-39

.71

2-13

8,268

14,882

(a) Sample as received.

(b) Same sample calculated to an ash- and moisture-free basis.

Peacock coal. Peacock coal is not a distinct variety of coal but
rather a condition in which either anthracite or bituminous coal may
be found. It is of considerable interest in some localities because of
its beauty and abundance. It has received its name from its irides-
cent colors which resemble those o the peacock in their changing
lights. This play of colors is similar to that produced by a film of
oil or of iron oxide on water and is due to the same cause, viz., re-
fraction and interference of the rays of light in passing through the
film. This coal is found only in the upper levels of the mine, par-
1 Stock, 22d Ann. Kept., U. S. Geol. Survey, p. 74, 1900-1901.

JET 97

ticularly where the seam and roof slate are much fractured, thus per-
mitting surface waters to percolate through the fissures in the coal
and to deposit thin films of iron oxide along the cracks. The film may
in a few cases be due to traces of crude oil or to sulphur dioxide but
the main cause is the iron oxide produced by the oxidation of iron
pyrite near the surface where the oxygen of the air can attack the
iron sulphide. That it might be due in some rare cases to sulphur
dioxide gas, which may be set free in the weathering of iron sulphide,
is suggested by the fact that a burning sulphur match brought close
to a fragment of coal will often produce a similar iridescent film on the
surface of the coal.

Other Combustible Substances Entering Into the Composition
of Some Coal Seams

Jet (Fr. Jayet, Ger. Gagath, Greek, Gagates). This is a black,
rather fibrous to compact substance capable of taking a good polish
and used in Europe for the manufacture of ornaments, especially
for those worn in mourning. Formerly an industry on a small scale
was carried on in France at Sainte-Colombe sur THero, Departement
de PAude. In Yorkshire, England, a few tons of this material have
been produced and it is said to have been worth about a shilling a
pound. The composition of jet is as follows: 1

Volatile matter 37 . 90 per cent

Ash 1.70 "

Carbon 61 .40 "

Its specific gravity varies from 1.26 to 1.3.

Jet is generally described as a variety of lignite but Prestwich 2
speaks of it as a wood converted into a sort of cannel coal. While
jet may resemble cannel a little in physical character, from our present
knowledge of cannel it is evident that it cannot resemble it in origin
since all writers agree that jet is altered wood while cannel is made
up almost entirely of plant spores. The jet found in the Jurassic
rocks on the Yorkshire coast of England is believed from structure
detected in thin sections to have been formed mainly from coniferous
wood which was allied to the Araucarian pines. It is also considered
that the trees drifted to their present position since the jet is now

1 Descloizeaux, A., Manuel de mineralogie, Tome 2, p. 332, 1893.

2 Prestwich, J., Chemical, physical, stratigraphic geology, p. 142.

9 8

VARIETIES AND RANKS OF COAL

found associated with Ammonites and other marine fossils. It oc-
curs in Asia Minor, Spain and Bohemia as well as in England and
France.

Natural coke or carbonite. In certain cases where igneous rocks
have intruded bituminous coal seams the coal has been transformed
m - into natural coke more or less

resembling artificial coke but
usually differing from the latter
chiefly in the percentage of the
volatile constituents which it
contains and in its more com-
pact character. Taff 1 has sug-
gested that the greater percentage
of volatile constituents in the
natural coke may be due to the
lack of opportunity for the es-
cape of these gases and to the
possible accession of gases to the
coke from the adjacent coal seam
after it has cooled. The coke
shows a typical columnar struc-
ture varying in degree of perfec-
tion of the columns (Fig. 16),
and with the columns normal to
the surface of contact between
the igneous rock and the coal
which has been coked. The ex-
tent to which the coal is coked

FIG. 16. Natural coke, or carbonite

from Hesse (specimen in collection of

Museum Nationale d'Histoire Naturelle,

Paris).

varies greatly. Other things
being equal, there will be a fairly
close relation between the thick-
ness of the coked zone and that
of the igneous rock, the former varying directly as the latter, but
no definite rule can be established because cases have been noted
where almost no observable coking has occurred, while in other cases
the coal is coked out of all proportion to the size of the intruding
rock. This condition is well understood when one considers that

i Taff, J. A., Natural coke in the Wasatch Plateau. Science, N. S., Vol. 23, p. 696, 1906.

NATURAL COKE OR CARBONITE 99

igneous masses entering the coal seams at various times or in differ-
ent places may vary greatly in temperature and in the amount of
the hot vapors and gases which they carry. In some cases the
latter may escape along the bedding planes in the coal deposits
and conduct the heat some distance from the igneous rock. The
basic igneous rocks, being more fluid than the acid are often capa-
ble of intruding themselves into narrow fissures in ways in which
the more viscous acid rocks cannot.

In the United States natural coke is common in Colorado, Utah,
and New Mexico, and it is also abundant in Mexico 1 and Alaska where
the coals have been extensively intruded by igneous rocks.

This coke has a regular fracture, is dark gray to iron-black in color,
and its texture varies from distinctly porous to compact. The luster
is graphitic to submetallic. It often grades into anthracite which in
turn passes into the bituminous coal of the seam. In most places it
makes excellent fuel. The following analyses indicate the per-
centage composition of the coke, the adjacent coal, and a sample of
artificial coke.

I II III IV V VI VII VIII* ix* x*

Moisture 8.10 0.32 0.57 3.86 13.42 3.28 0.184

Volatile matter 40.20 20.38 0.39 35.34 5.83 1.64 0.552 20.30 12.20 4.70

Fixed carbon .45.91 65.90 78.24 53.28 61.50 89.14 88.726 79.70 87.80 95.30

Ash

Sulphur. .
Hydrogen
Carbon. .

5.76 13.10 20.80 7.52 19.25 9.22 9.993 8.29 9.73 45.96
0.54 0.64 0.48 0.83 0.533 2.07 i. ii 0.15

5-48 3-39
72.66 61.55

Nitrogen 1.17 0.81

Oxygen 12.53 14.52

Air-drying loss . 2 . 60 1 1 . 60

B.t.u 13,068 9895

I. Analysis quoted by Taff of coal in seam in Wasatch Plateau.
II. Natural coke from same seam.

III. Natural coke from Cokedale Mine, Colorado. U. S. Bur. of Mines, Bull. 22, pt. i,

p. 69.

IV. Coal taken i foot from natural coke and z\ feet from a dike. Walsen Mine,

Colorado. Op. cit. under III, p. 65.
V. Same locality as IV but close to small dike and coke.
VI. Artificial coke.

VII. Artificial coke from the coal of the Connelsville basin, Pa. U. S. Geol. Survey.
VIII. Coal in the seam removed from the influence of the eruptive.
IX. Coal 0.3 metres from the igneous rock.
X. Coal in contact with the eruptive.

* Analyses by G. von Rath. Contactverhaltnisse Zwischen Kohle und einem basischen
Eruptivgestein bei Fiinf kirchen : Neues Jahrbuch, I, pp. 274-277, 1880.

1 Durable, E. T., Natural coke of the Santa Clara Coal-Field, Sonora, Mexico. Trans.
Am. Inst. Min. Eng., Vol. 29, pp. 546-549, 1899.

100 VARIETIES AND RANKS OF COAL

The greater percentage of ash shown in the analyses of the coke
than in the analyses of the coal from the same seam is often only rela-
tive, but in some cases it is probable that silica and possibly other
mineral constituents have been added to the seam by the igneous
rock in its immediate vicinity.

FIG. 17- Intrusion of diabase into a coal seam in Alaska, producing
natural coke. (From a sketch by W. R. Crane.)

Mineral charcoal or "mother of coal" (Fr. Fusain). In the
different varieties of coal from lignite to anthracite there are dull
laminae, lenses, and irregular bands of a black to dark-grey material
which, on account of its resemblance to charcoal is known as
" mineral charcoal" or among many of the miners as " mother of
coal." It may take the form of an iron-gray, almost powdery
material or it may show the outline of blackened fragments still
retaining some of the original woody structure and fibers. In
some cases even the most delicate structures of the leaf are pre-
served. When cut with a knife it shows much the same consistency

MINERAL CHARCOAL OR MOTHER OF COAL" 101

as wood charcoal but is more sooty and crumbling. It soils
the fingers. Various explanations have been offered for its origin.
Daubree 1 in 1844 ascribed it to forest fires started by lightning, burn-
ing in the swamps where the coal vegetation was laid down. As early
as 1858 Rogers 2 recognized that it was due to some alteration which
the vegetation suffered before being buried and this explanation is
supported by White, 3 who considers that the association of the various
woody materials, the preservation of the rods, and the delicate 'fern-
leaf fragments make the forest fire hypothesis untenable. He be-
lieves that the charcoal has originated as a result of the greater amount
of decomposition which the vegetation suffered before being buried in
the bog. On the other hand, Jeffrey 4 still clings to the theory that
the forest fire was the agent which produced the charcoal.

A consideration of the actions of forest fires in our modern swamps
and peat-bogs in the northern portions of the continent, in addition
to the arguments put forth by White, oppose the forest fire hypothesis.
It is seldom that the fire leaves the charred materials in such quan-
tities in proportion to the ash and in such associations in relation to
the coarse and fine fragments as that in which they must generally
have been left to produce the deposits now found in coal. It is
possible that an occasional mass of charcoal resulted from fire but
improbable that the greater part of the mineral charcoal was produced
in that way. The best explanation is found in the greater alteration
of the vegetal matter in parts of the swamp exposed to dry rot where
the water was low.

It is evident that carbonite and mineral charcoal have at times
been confused by some writers. 5

Analyses show that mineral charcoal usually differs considerably
in chemical composition from the other portions of the coal seam
in which it occurs. The following analyses were made from a seam
in which the charcoal occurs irregularly throughout the mine and is
there known as " mother of coal." It is not found over 9 inches from
the bottom of the seam and it always pinches out gradually. The

1 Daubree, A., Compt. Rend., Vol. 19, p. 126, 1844.

2 Rogers, H. D., Geology of Pennsylvania, Vol. 2, p. 993, 1858.

3 White and Thiessen, The origin of coal. U. S. Bur. of Mines, Bull. 38, p. 33, 1913.

4 Jeffrey, E. C., Jour, of Geology, Vol. 23, p. 218, 1915.

6 Heinrich, O. J., The Mesozoic formation in Virginia. Trans. Am. Inst. of Min.
Eng., Vol. 6, pp. 243-244, 1877-78.

102 VARIETIES AND RANKS OF COAL

thickness of the charcoal varies from zero to 3 inches. There are
usually very small bright streaks running through the dark gray,
which always has a dull luster. The writer is indebted to Mr. H. B.
Northrup for these analyses.

I II

Moisture o . 62 per cent o . 23 per cent

Volatile matter 23 . 05 " 7.11 "

Fixed carbon 68.86 " 90.99 "

Ash 7.47 " 1.67 "

Sulphur 1.19 " o . 23 "

I. The coal from a seam in the Glenview Mine, Decatur Twp., Clearfield Co., Pa.
II. Mineral charcoal from the same seam.

Resinous substances. In addition to the substances described
there are often found in coals, particularly in the younger and less
altered coals such as the lignites, large and small masses of amber-
like substances which represent the resins from various trees growing
in the coal swamps. 1 To these the name Retinite is often applied in a
general way. In the Tertiary lignites near Gore, New Zealand,
masses of this retinite as large as a man's head may be seen and
in some of the lignite of the western United States resins are found
in considerable quantities. The following are examples of these
resins from coal seams in various localities. 2

Ambrite (C 4 oH 6 6O 5 approx.): A yellowish-gray, subtransparent,
amorphous resin which breaks with a conchoidal fracture. The
hardness is 2 and the specific gravity 1.034. The luster is greasy.
It becomes strongly electrified when subjected to friction. An an-
alysis by Maly shows:

Ash o. 19 per cent

Hydrogen 10 . 58

Carbon 76.53

Oxygen 12 . 70 "

It burns with a yellow smoky flame. It is insoluble in ether, oil of
turpentine, benzine, chloroform, and dilute acid.

This resin is described by Hochstetter as occurring in large masses
in several of the coal fields of New Zealand. It is so much like the
Kauri gum of the North Island that it is sometimes exported with it.

1 White, David, Resins in Paleozoic plants and in coals of high rank. U. S. Geol.
Survey, Prof. Paper 85 E, 1914.

2 For full description of these and related substances see Dana's System of mineralogy,
pp. 1002-1014, 1892. Also, Descloizeaux, Manuel de mineralogie, Tome 2, p. 34, 1893.

RESINOUS SUBSTANCES 103

Bathmllite: This substance forms dull brown lumps in the Tor-
banite in Scotland and since it usually occurs as a cavity filling it is
not known whether it is a resin or a secretion from the Torbanite
which it resembles in composition although containing less oxygen.

Duxite: A dark brown, opaque resin from the lignite at Dux,
Bohemia. Its specific gravity is given as 1.13 and its chemical com-
position according to Fischer is as follows :

Moisture 2.72 per cent

Ash 1.94 "

Sulphur o . 42 "

Hydrogen 8 . 14 "

Carbon 78 . 25 "

Oxygen 13-19 "

This is in general similar to Muckite and Walchowite except that
they are lighter colored. Neudorfite from the coal beds at Neudorf,
Moravia is very similar in composition.

Middletonite: This substance, which was named by Johnston 1
from the Middleton Collieries near Leeds, England, occurs about the
middle of the main coal in little round masses. These masses are
seldom larger than a pea and are generally in thin layers less than T \
inch in thickness between the layers of coal. It is hard and brittle,
and its specific gravity is about 1.6. In color it is reddish-brown in
reflected light and deep red in transmitted light. The luster is resin-
ous. It blackens on exposure to the air and then cannot readily be
distinguished from the coal except by its luster. It is unaffected by
heat at 400 F. and it burns like resin. It is soluble in cold sulphuric
acid but it is very slightly soluble in alcohol, ether and oil of turpentine.
An analysis shows the following composition:

Hydrogen 8 . 007 per cent

Carbon 86.437

Oxygen 5 . 563 "

The formula suggested is (C 2 oHi + H 2 O) which resembles that for
the hydrate of the oil of turpentine.

Succinite: This substance is commonly known as amber. It is
found in considerable quantities on the coast of the Baltic. It occurs
as irregular masses which have a conchoidal fracture. The hardness
is about the same as that of anthracite coal, 2-2.5, an d the specific
gravity is 1.05 to 1.09. The color is yellow or reddish-brown and the
luster resinous. It is negatively electrified by friction and it softens

1 Johnston, F. W., The Phil. Mag., Vol. 12, p. 261, 1838.

104 VARIETIES AND RANKS OF COAL

at 150 C. Its composition is represented by the following analysis
by Schrotter:

Hydrogen 10.22 per cent

Carbon 78.82 "

Oxygen 10 . 94 "

There is usually a little sulphur present in the form of an organic
compound. Succinite occurs in the bituminous coals of the southern
part of France and in lignite in various localities.

Wheelerite: In the Cretaceous lignite beds of New Mexico Loew 1
found a yellowish resin filling fissures and interstratified with the
coal. This was named Wheelerite after Lt. G. M. Wheeler. The
composition is as follows:

Hydrogen 7.31 per cent

Carbon 73 . n "

Oxygen 19 . 58 "

It is almost entirely dissolved in alcohol or ether and is partially
soluble in carbon bisulphide. It is soluble also in sulphuric acid,
producing a brown solution, and with nitric acid it evolves nitrous
fumes. It melts at 154 C.

There are numerous other resins similar in many respects to those
described above. Among these might be mentioned lonite from the
lignite of lone Valley, California; Koflach from the Tertiary brown
coals of Styria; Rosthornite, the brown to garnet-red material which
forms lenticular masses in the coal of Carusthia; Schleretinite from
the Coal Measures of Wigan, England; Tasmanite from the bituminous
shales of Tasmania; Trinkerite which forms large amorphous masses
of a hyacinth-red to chestnut-brown color in the brown coal near
Albona, Istria. Pyroretinite which resembles the resin of Pinus
abies is said to occur in masses from the size of a nut to that of a
man's head in the brown coal near Ausseg, Bohemia. Its specific
gravity runs from 1.05 to 1.18 and its hardness about 2.5. Rochled-
erite occurs in large reddish-brown resin-like masses in the brown coal
of Zweifelsruth in Eger, Bohemia.

1 Loew, O., On wheelerite, a new fossil resin. Am. Jour. Sci. $d Series, Vol. 7, p. 571,
1874.

CHAPTER V
THE CLASSIFICATION OF COALS

Introduction

There have been in use since the earliest days of the coal trade
certain names which distinguish different varieties of coal, such as
anthracite, bituminous, and lignite. These names, or their equiva-
lents, are in general use almost throughout the world. As the im-
portance of the coal trade increased, however, it was realized that some
more definite means of classifying coals according to their composition
and heating value was desired because the lines of distinction between
the varieties used in the past were not sufficiently definite for prac-
tical purposes.

Frazer's Classification

One of the first in this country to attempt a definite classification of
coals on the basis of their composition and heating value was Persifor
Frazer, Jr. 1 He based his classification on the ratio of the fixed car-
bon to the volatile combustible matter (C : V.Hc). He states that
as early as 1844 W. R. Johnson had used the same principle and had
recognized the ratio of the volatile to fixed combustible matter as a
logical basis for the classification of coals. After various attempts to
make the fuel ratio of the different coals fit the descriptions of the
varieties suggested by H. D. Rogers in 1858, Frazer concluded
that it is only possible to classify the coals according to their fuel ratio
within wide limits, and suggests the following divisions:

C
V.Hc

Hard-dry anthracite 100-12

Semianthracite 12-8

Semibituminous 8-5

Bituminous 5-0

The table is deficient for modern use because it does not distinguish

1 Frazer, Persifor, Jr., Classification of coals. Second Geol. Survey of Pennsylvania,
Kept. M. M., pp. 128-144, 1879. Also Trans. Am. Inst. Min. Eng., Vol. 6, pp. 430-451,
1877, and Vol. 36, p. 825, 1906

105

106 THE CLASSIFICATION OF COALS

subbituminous coal and lignite from bituminous coal and as stated
by Frazer the ratio limits had to be arbitrarily chosen. The table
represents, however, a considerable advance over any previous work
and it sets forth a principle which has become deeply established in
the coal trade.

In discussing Frazer's classification, A. S. McCreeth 1 calls attention
to the fact that the sulphur content of the coal should be taken into
consideration since it is partly volatilized in coking, and he suggests
that the portion volatilized should be subtracted from the volatile
hydrocarbon percentage and added to that of the fixed carbon.

Classification on basis of Moisture Content

In 1903 Collier 2 suggested that all coals with a moisture content of
10 per cent or more should be classed as lignite, and those with less
than 10 per cent as bituminous, but his classification has proved en-
tirely unsatisfactory.

Campbell's Classification

After extensive studies of coal for the purpose of obtaining a satis-
factory classification Campbell 3 came to the following conclusions:
(i) For the higher grades of coal the fuel ratio may be used as a satis-
factory means of separation but it does not properly separate the
lignites and bituminous coals. (2) The percentage of fixed carbon
cannot be used as a satisfactory basis. (3) The calorific value cannot
be used since many of the bituminous coals are of higher calorific
value than the best grades of anthracite. It is, however, fairly satis-
factory for the lignites and bituminous coals. (4) The percentage of
hydrogen present is valueless as a basis of classification. (5) A classi-
fication according to the carbon content is satisfactory in a general
way as there is a fairly regular decrease in the carbon content from that
of anthracite to that of lignite. The separation between anthracite
and semibituminous is not marked and there are many exceptions
to the rule. (6) The carbon-hydrogen ratio is regarded as the most
satisfactory basis for classification.

1 McCreeth, A. S., Second Geol. Survey of Pennsylvania, Rept. M. M., p. 157, 1879.

2 Collier, A. J., Coal resources of the Yukon, Alaska; U. S. Geol. Survey, Bull. 218,
1003.

3 Campbell, M. R., The classification of coals. Am. Inst. of Min. Eng., Vol. 36, p. 324,
1906. Also, Report on the operation of the coal testing plant. U. S. Geol. Survey,
Prof. Paper 48, pt. i, 1906.

SEYLER'S CARBON-HYDROGEN CLASSIFICATION

107

He then groups the coals as follows in a tentative classification,
the ratios of the higher coals being rather indefinite owing to lack of
ultimate anlyses.

Carbon-Hydrogen Ratio.

Group A (Graphite) oo-(?)

Grouo B
Group C
Group D
Group E
Group F
Group G
Group H
Group I
Group J
Group K
Group L

(Semianthracite) 26(?)-23(?)

(Semibituminous) 23(?)-2o

20-17

(Bituminous) I4 '

I2.5-II.2

(Lignite) 11.2- 9.3

(Peat) 9-3- (?)

(Wood, Cellulose) 7.2

Seyler' s Carbon-Hydrogen Classification

Seyler 1 had previously published the following classification. It is
based on the hydrogen and carbon in the pure coal. The genera,
which are arranged vertically, are distinguished by their hydrogen
content while the species are arranged horizontally and separated
according to their percentage of carbon. This table is taken from
Pollard. 2

1 Seyler, C. A., Chemical classification of coal. Proc. S. Wales Inst. Eng., Vol. 21,
p. 483 and Vol. 22, p. 112. Also, Colliery Guardian LXXX pp. 17-19, 80-82 and 134-136.

2 Strahan, A., and Pollard, W., The coals of S. Wales. Mem. Geol. Survey of England
and Wales, 2d ed., pp. 58-59, 1915.

io8

THE CLASSIFICATION OF COALS

Carbon

Anthracitic

Carbon-
aceous

Bituminous

Lignitious

Meta.

Ortho.

Para.

Meta. Ortho.

Carbon
over 93 . 3

93-3-91.2

91.2-89.0

89.0-87.0

87.0-84.0

84-80 80-75

Perbitu-
minous
genus

Hydrogen
over 5. 8
per cent

Perbitu-
minous
(Per-meta-
bitumi-
nous)

Perbitu-
minous
(Per-ortho-
bitumi-
nous)

Perbitu-
minous
(Per-para-
bitumi-
nous)

Perligni-
tious

Bitumi-
nous
genus
Hydrogen
5-0-5-8
per cent

Pseudobi-
tumi-
nous
species

Metabitu-
minous

Orthobitu-
minous

Parabitu-
minous

Lignitious
(Meta)
(Ortho)

Semibitu-
minous
genus

Hydrogen

4-5-5-0
per cent

Semibitu-
minous
species

(Ortho-
semibi-
turni-
nous)

Subbitu-
minous
(Sub-meta-
bitumi-
nous)

Subbitu-
minous
(Sub-or-
thobitu-
minous)

Subbitu-
minous
(Sub-para-
bitumi-
nous)

Subligni-
tious
(Meta)
(Ortho)

Carbon-
aceous

genus

Hydrogen
4.0-4.5
per cent

Semian-
thracitic

species

Carbon-
aceous

species

(Ortho-
carbon-
aceous)

Pseudo-
carbon-
aceous
(Sub-
metabi-
tumi-
nous)

Pseudo-
carbon-
aceous
(Sub-or-
thobitu-
minous)

Pseudo-
carbon-
aceous
(Sub-para-
bitumi-
nous)

Anthra-
citic
genus
Hydrogen
under 4
per cent

Orthoan-
thracitic

Pseudoan-
thracite

Subcar-
bon-
aceous

Pseudoan-
thracite

Sub-meta-
bitumi-
nous

Pseudoan-
thracite

Sub-ortho-
bitumi-
nous

Pseudoan-
thracite

Sub-para-
bitumi-
nous

Pollard shows that in the coals analysed from the Welsh field the
hydrogen-carbon ratio falls fairly satisfactorily into Seyler's classi-
fication. The carbon-hydrogen ratios given by the U. S. Geological
Survey do not fit the Welsh anthracites very well as many of them
have a ratio below 26.

PARR'S CLASSIFICATION

109

Grout's Classification based on Carbon Content

In an article published the year after Campbell's classification
appeared, Grout 1 criticizes the use of the carbon-hydrogen ratio as
not being reliable and states that if total carbon in ash- and moisture-
free coal had been considered the separation between lignite and
bituminous coal would have been very satisfactory. The chief
objection made to the carbon-hydrogen ratio is the fact that although
the hydrogen content of lignite and bituminous coal is not so very
different, the variation may amount to one-third of the total and thus
give a large difference in ratio in coals which are not markedly differ-
ent in other respects; on the other hand, it may throw two coals
together which are unlike in many important respects. The diffi-
culty in sampling the low grade coals so that all collectors may be
able to get the same amount of moisture and therefore the same
amount of hydrogen in the coal from the same seam is a further ob-
jection to Campbell's carbon-hydrogen ratio since it is based on too
variable a factor.

The following is Grout's classification based on fixed carbon for
those coals above bituminous, and on fixed carbon and total carbon
for bituminous coals and those of lower grade.

Graphite ............................... Fixed carbon over 99 per cent

Anthracite .............................. Fixed carbon over 93 "

Semianthracite .......................... Fixed carbon 83-93 "

Semibituminous ......................... Fixed carbon 73-83 "

Bituminous:

grade ...........................

Cannel / Fixed carbon 35~48

....... I Total carbon 76.2-

76.2-88

Peat and turf / Fixed carbon below 55

Peat and turf ........................... ( Total carbon bdow

Wood

Parr's Classification

Parr, 2 in his classification, considers that the term volatile combus-
tible as it has generally been used is incorrect since it includes some

1 Grout, F. F., The composition of coals. Econ. Geology, Vol. 2, pp. 225-241, 1907.

2 Parr, S. W., Illinois Geol. Survey, Bull. 3, 1906. Also, The classification of coals.
Jour. Am. Chem. Soc., Vol. 28, p. 1425, 1906.

THE CLASSIFICATION OF COALS

hydrogen, oxygen, and nitrogen, which are non-combustible. The
hydrogen present as hydrocarbons is combustible but that combined
with oxygen in water is not. For example, in a Pocahontas coal with
18.7 per cent volatile matter 14.5 per cent is combustible hydrocarbons
and 4.2 per cent is non-combustible hydrogen, oxygen and nitrogen.
This inert matter should be taken into consideration since it is not
an asset to the fuel.

In this classification total carbon (C) and fixed carbon (fc) are
determined from analysis. The volatile carbon (vc) unassociated
with hydrogen is obtained by subtracting the percentage of fixed
carbon from that of total carbon (C fc = vc). The inert volatile
matter is obtained by subtracting from 100 per cent the sum of total
carbon + sulphur -f ash + water -f hydrogen, which is not united
with oxygen in water and is, therefore, free to burn and produce heat.
To reduce this remainder to a pure fuel basis it is divided by 100 less
the sum of ash and water. The derived formula on which the fol-

lowing table is based is vc

100

This ratio serves to differentiate

the coals above bituminous. In the bituminous and lower grades of
coal the inert volatile matter, which is so much more abundant in
these coals, is taken into consideration. The classification is as
follows :

IOO

Inert volatile

Anthracites proper .

. . . Below 4

Anthracitic \

Semianthracites . . .

. . . 4-8

Semibiturninous

10 i^

A 20-32

5-io

Bituminous

Bituminous proper

B 20-27
C 32-44
D 27-44

10-15
5-io
10-15

Black lignite
Brown lignite

27 up
27 up

16-20
2030

In taking examples of the various analyses of coals tested by the
U. S. Geological Survey at the St. Louis plant, Parr 1 shows that they
readily follow this classification.

1 U. S. Geol. Survey, Prof. Paper 48, 1906.

WHITE'S CLASSIFICATION BASED ON CARBON in

A further formula is suggested for the purpose of determining what
Parr chooses to call the " gross coal index," or the amount of any coal
necessary to give 100 pounds of pure fuel. It is found by adding
together the carbon, sulphur ,and combustible hydrogen, (these three
constituents being regarded as the only true heat-producing factors
in the coal) dividing the sum by 100, and 100 by the quotient. Thus
a Dakota lignite contains: C 52.66 per cent; H 1.83 per cent; and 5
2. 02 per cent = 56.51. The " gross coal index" for this coal would

be = 177, or it would require 177 pounds of it to make 100

-5651
pounds of pure fuel.

Grout's classification resembles this one of Parr's in providing two
factors for fixing the position of, the coal and it has the advantage of
being simpler in its application.

White's Classification based on Carbon Oxygen + Ash

Content

Another method of classifying coals has been suggested by White 1
in making determinations of the anti-calorific influence of oxygen.
As a result of an investigation of all available ultimate analyses it
was found that ash and oxygen possess almost equal anti-calorific
values, the former having slightly more than the latter. This was
found to be true also for moisture-free coal. If two coals alternate
in the percentages of ash and oxygen while the other constituents
remain constant the calorific value changes very little. Since carbon
is the principal calorific element in the fuel it seems appropriate that
it should be taken as one factor and (oxygen -f ash) as the other in
determining the calorific value. It is found, therefore, that the
ratio C : (O + ash) gives a quotient which corresponds very closely
to the determined calorific value of the coal, not varying more than
i per cent, as a rule, from an efficiency curve. The sulphur, available

hydrogen f H j and nitrogen seem to play a small part in con-
trolling the calorific value of the fuel compared with that of the
carbon, oxygen, and ash. The hydrogen is the most potent element
of the three and its influence is shown in the special types of coal
such as those of the boghead-cannel group.

1 White, David, The effect of oxygen in coal. U. S. Geol. Survey, Bull. 382, 1909.

112 THE CLASSIFICATION OF COALS

It was found, further, that the relation of the ratio C : (O + ash)
to the calorific value becomes much less distinct in coals undergoing
anthracitization and having over 79 per cent fixed carbon in the pure
fuel, or in those which have been weathered.

This classification is of great scientific interest in its bearing on the
calorific value of coals but it has little application in classifying coals
according to the terms which are familiar in the coal trade.

There is one strong objection, from a practical standpoint, to all
the preceding classifications except that of Frazer in the fact that they
require ultimate anlyses. If possible, the making of ultimate an-
alyses for classification purposes should be avoided since they are
always costly. Parr has met this objection to a considerable degree
by devising an apparatus by means of which the total carbon may be
readily determined and he has also prepared a curve from which the
available hydrogen may be obtained. This curve is constructed on
the principle that the available hydrogen is combined with volatile
carbon in the form of hydrocarbons and that the percentage of avail-
able hydrogen, therefore, bears a fairly definite relation to the per-
centage of volatile carbon. Since the latter is easily obtained by sub-
tracting the fixed carbon from the total carbon it is not difficult to
obtain the available hydrogen from the curve.

Dowling's Split Volatile Ratio Classification

In order to avoid the necessity of making an ultimate analysis
Dowling 1 has suggested a classification based on what he calls the
" split volatile ratio" This system is adopted in order to take into
account the volatile matter, which is available for the production of
heat and that portion which is inert and therefore should be placed
with the moisture as anti-calorific material. The formula used is,

Fixed carbon -f i volatile combustible TT7 ~ , . .,

.., . ^ . When the quotients result-

Moisture + J volatile combustible

ing from this ratio are compared with those obtained from the car-
bon-hydrogen ratio they are found to be almost equally satisfactory.
The various coals may be grouped according to this classification in
the following order:

1 Dowling, D. B., Classification of coals by the split volatile ratio. Can. Min. Joui.
pp. 143-146, April 15, 1908. Also, Can. Geol. Survey, Rept., No. 1035, P- 43

CLASSIFICATION ADOPTED BY GEOLOGICAL CONGRESS 113

Anthracite 15 up

Semianthracite 13-15

Anthracite coal 10-13

High carbon bituminous 6-10

Bituminous 3 . 5-6

Low carbon bituminous 3-3 . 5

Lignitic coal 2 . 5-3

Lignite 1-2-3.5

This split volatile ratio was adopted in part of the following classi-
fication of the coals of the world by the Twelfth International Geol-
ogical Congress 1 and also in a later work by Bowling on the coal
resources of Canada. 2

Classification Adopted by the International Geological Congress

CLASS A

(1) Burns with short, blue flame; gives off 3 to 5 per cent of volatile
combustible matter.

._ , . Fixed carbon
Fuel ratio: . - = 12 and over.
Volatile matter

Calorific value, 8000 to 8330 calories, or, 14,500 to 15,000 B.t.u.
Mean composition,

Carbon 93 to 95 per cent

Hydrogen 2 to 4 "

Oxygen and nitrogen 3 to 5 "

(2) Burns with slightly luminous, short flame and little smoke;
does not coke, and yields from 7 to 12 per cent of volatile matter.

Fuel ratio, 7 to 12.

Calorific value generally 8300 to 8600 calories, or 15,000 to 15,500
B.t.u.
Mean composition,

Carbon 90 to 93 per cent

Hydrogen 4 to 4.5 "

Oxygen and nitrogen 3 to 5.5 "

CLASS B

(i) Burns with short, luminous flame and yields 12 to 15 per cent
volatile matter; does not readily coke.
Fuel ratio, 4 to 7.

1 Coal resources of the world. Vol. i, Toronto, Canada, 1913.

* Coal fields and coal resources of Canada. Can. Geol. Survey, Mem. 59, 1915.

114 THE CLASSIFICATION OF COALS

Calorific value generally 8400 to 8900 calories, or 15,200 to 16,000
B.t.u.
Mean composition,

Carbon 80 to 90 per cent

Hydrogen 4 5 to 5

Oxygen and nitrogen 5 . 5 to 12 "

(2) Burns with luminous flame and yields from 12 to 26 per cent
volatile matter; generally cokes.

Fuel ratio, 1.2 to 7.

Calorific value 7700 to 8800 calories, or 14,000 to 16,000 B.t.u.

Mean composition,

Carbon 75 to 90 per cent

Hydrogen 4. 5 to 5.5 "

Oxygen and nitrogen 6 to 15 "

(3) Burns freely with long flame; withstands weathering but frac-
tures readily and occasionally has moisture content up to 6 per cent;
volatile matter up to 35 per cent; makes porous, tender coke.

Fixed carbon + \ volatile

! * = 2 . C tO 3 . ^

Hygroscopic moisture + J volatile

Calorific value 6600 to 7800 calories, or 12,000 to 14,000 B.t.u.

Mean composition,

Carbon 70 to 80 per cent

Hydrogen 4-5 to 6 "

Oxygen and nitrogen 18 to 20

CLASS C

Burns with long, smoky flame; yields from 30 to 40 per cent vola-
tile matter on distillation, leaving very porous coke. Fracture
generally resinous.

Calorific value 6600 to 8800 calories, or 12,000 to 16,000 B.t.u.

CLASS D

Contains generally over 6 per cent of moisture; disintegrates on
drying; streak brown or yellow; cleavage indistinct.

(i) Moisture in fresh-mined, commercial output, up to 20 per cent.
Fracture generally conchoidal.
Drying-cracks irregular, curved lines.
Color generally lustrous black, occasionally brown.
Fixed carbon + volatile

Hygroscopic moisture + \ volatile

= 1.8 to 2.5

GRUNER'S CLASSIFICATION 115

Calorific value 5500 to 7200 calories, or 10,000 to 13,000 B.t.u.
Average composition,

Carbon 60 to 75 per cent

Hydrogen 6 to 6 . 5 "

Oxygen and nitrogen 20 to 30

(2) Moisture in commercial output over 20 per cent. Fracture
generally earthy and dull.

Drying-cracks generally separate along bedding planes and often
show fibrous (woody) structure.

Color generally brown, sometimes black.

Calorific value 4000 to 6000 calories, or 7000 to 11,000 B.t.u.

Average composition,

Carbon 45 to 65 per cent

Hydrogen 6 to 6.8

Oxygen and nitrogen 30 to 45 "

In the above classification, letters are substituted for names. In
a general way the classification conforms to the nomenclature used
in America, as follows:

AI = Anthracite coal.

A z = Semianthracite coal.

Bi Anthracitic coal and high carbon bituminous coal.

B 2 = Bituminous coal.

Bz = Low carbon bituminous coal.

C = Cannel coal.

DI = Lignitic or subbituminous coal.

Dz = Lignite.

Gruner's Classification

In his classification of French coals Gruner 1 takes into consideration
the fixed carbon and volatile matter as well as the constituents of the
ultimate analysis. He also makes use of the ratio of hydrogen to
(oxygen + nitrogen). No provision is made for lignite, subbitumi-
nous coal, or cannel. The following table is a slightly abbreviated
compilation of Gruner's tables. As previously mentioned the term
"houille" in French corresponds to bituminous coal in America, and
"charbon" is the general term used for coal.

1 Gruner, E., and Bousquet, G., Atlas general des houilleres. Deuxieme partie,
Texte p. 16, 1911.

THE CLASSIFICATION OF COALS

Class or type of coal
and commercial
name in France

Proportion oi
coke in 100
parts of pure
coal

Proportion of
volatile matter
in loo parts of
pure coal

Nature and ap-
pearance of
coke

Real calorific
power

Industrial cal-
orific power.
Water at o
vaporised at
112 by i kgm.
of pure coal
burned

Per cent

Calories

Kgms. of water

i. Houilles se-
ches (dry)
& longue
flamme.
Houilles flam-
bantes.

55-60

45-40

Powdery or
slightly
fused.

8000-8500

6.70-7.50

2. Houilles
grasses (fat)
a longue
flamme.
Charbons a
gaz.

60-68

42-32

Completely
agglomer-
ated and
very often
fused.

8500-8800

7.60-8.30

3. Houilles
grasses (fat)
proprement
dites. Char-
bons de forge
et Houilles
marechales
(smiths).

68-74

32-26

Fused and
more or less
swollen.

8800-9300

8.40-9.20

4. Houilles
trasses (fat)
courte
flamme.
Charbons a
coke.

74-82

26-18

Fused, com-
pact.

9300-9600

9.20-IO.OO

5. Houilles
maigres (lean)
ou anthracit-
euses char-
bons demi-
gras. Char-
bons quart-
gras.

82-90

I8-IO

Slightly
fused, very
often powd-
ery.

9200-9500

9.00-9.50

6. Anthracites.
Charbon
maigre (lean)
anthracite.

90-92

10-8

Powdery,
often de-
crepitated.

9000-9200

9.00

GRUNER'S CLASSIFICATION

117

Carbon

Hydrogen

Oxygen anc
Nitrogen

. + N

Designation in
Germany
(Ruhr Basin)

Designation in
Belgium

Designation in
England

Ratio H

Per cent
I. 70-80

Per cent

Percent

5-5-4-5

I9-5-I5-5

Between
4 and 3

Flamm-
Kohle

Flenus
sees

Splint coal

2. 80-85

5-8-5-0

14.2-10.0

Between
3 and 2

Gas-Kohle

Flenus
gras ou
Mons

Gas coal

3- 84-89

S-o-5-5

11.0-5.5

Between
2 and i

Fett-Kohle

Caking coal

4. 88-91

5-5-4-5

6-5-4-5

Nearly i

Fett-Kohle

Charbons
durs ou
Charleroi

Steam coal

5- 90-93
6. 93-95

4-5-4-0
4 . 0-2 . o

5-5-3-0

Less than

Mager-
Kohle

3-o

1-0.5

Anthrazit

Anthracite

Il8 THE CLASSIFICATION OF COALS

A number of experiments have shown that the lean (maigre) coals
are almost insoluble in the ordinary solvents such as aniline while
there is an increasing proportion of the fuel soluble, in passing from
the lean to the fat (gras) coals.

Ashley 's Use Classification

A classification has recently been suggested by Ashley 1 which is
intended primarily for the use of the person engaged in the coal
business and which he designates as a "Use Classification." The
main factors on which this classification are based are two ratios,
the first being the ratio of the fixed carbon to volatile matter and moist-

F c

ure combined ' and the second the fuel ratio and the
V.m. + rizU

fixed-carbon-moisture ratio (F.c.m. ratio). A double ratio is thus
made use of as in some of the previous classifications described. The
higher-rank coals are distinguished by their fuel ratio and the lower
ranks by the ratio of the moisture "as received" to fixed carbon.
These ratios are chosen because in the higher ranks of coal the moist-
ure changes little and the volatile matter much in relation to the
fixed carbon when one rank of coal is changed to another higher in the
scale by geological processes, while in the lower ranks there is a larger
proportional change in the moisture than in the volatile matter with
respect to the fixed carbon. The physical properties are also taken
into consideration since they depend largely upon the genesis of the
coal and must therefore be closely related to the chemical properties.
For example cannel coal differs greatly from ordinary bituminous
coal because of its different origin. The woody character of low-
grade coals is also considered.

A new departure in this classification is the adoption of locality
names for certain ranks and grades of coal. The coal of a distinctive
grade from a well-known mining locality takes the name of the lo-
cality with the name changed so as to end in ite. As examples,
Pocahontas coal would be known on the market as Pocahontite and
Hocking Valley coal as Hockingite. In addition to the use of these
terms for coal from those fields the names might be applied to the
same grade of coal from other localities, thus adopting the use of
locality names as they are used in mineralogy.

1 Ashley, G. H., A use classification of Coal. Trans. Amer. Inst. Min. Met. Eng.
LXIII, p. 782, 1920.

ASHLEY'S USE CLASSIFICATION

119

The following tables show examples of the application of these
ratios to the analyses of various typical coals throughout the country.
The first table shows the ratio of fixed carbon to volatile matter and
moisture combined, and the second the fuel ratio and fixed-carbon-
moisture ratio.

RATIO OF FIXED CARBON TO VOLATILE MATTER AND
MOISTURE COMBINED

( ~ F ',' 1J
\V.m. + H

Coal

Ratio

Coal

Ratio

Anthracite . .

IO 7 4-

Saint Clair Co., 111. coal

o 96

Bernice coal

6 8

Sangamon Co., 111. coal

o 84

Brushy Mountain, Va. coal . . .
Pocahontas coal . .

4.8

7 .7

Grundy Co., 111. coal
Sheridan, Wyo. coal

0.78

o 68

Sewell, New River, coal

2.8

Carney, Wyo. coal

o 62

Connellsville coal

2 .O

Gillette, Wyo. coal

o. <c6

Pittsburgh coal

1.6

Wood Co., Tex. lignite

O . cjO

Beaver River, Pa. coal

I .2

Houston Co., Tex. lignite

0.4-?

Gallatin Co., 111. coal

I .09

Williston, N. Dak. lignite

0.37

FUEL RATIO AND FIXED-CARBON-MOISTURE RATIO
(F.c.m. ratio.)

Coal

Fuel
ratio

Carbon
moisture

Coal

Fuel
ratio

Carbon
moisture

Anthracite

10+

io+(3o)

Saint Clair Co., 111. . .

1 .4-

4 O-6 O

Bernice

710

IO+(27)

Sangamon Co., 111. . .

I .4-

2 . "? 4 O

Brushy Mountain,
Va

r 7

IO+(26+)

Grundy Co , 111.

I 4.

2 O 2 ^

Pocahontas .

j e- e

IO+(24 O

Sheridan, Wyo.

I 4.

I 72 O

Sewell

2 < 3 C

io+(23)

Carney, Wyo.

I 4

I 4. I 7

Connellsville

I 85-2 *

IO-h(2T 5)

Gillette, Wyo

I 4-

I O I 4.

Pittsburgh

I .4-1.85

io-}-(i9 .5)

Wood Co., Tex

T 4

o 85-1 oo

Beaver River, Pa.
Gallatin Co., 111...

1.4-

i-4-

io+(i7)
6 .0-10.0

Houston Co., Tex
Williston, N. Dak.. ..

1.4-
1.4-

o . 65-0 . 85

0.5 -0.65

From these tables it is seen that the lignites fall between 0.5 and
i in the fixed-carbon-moisture ratio, most of the subbituminous
coals between i and 2 and the bituminous coals between 2 and io+.
Above this point the fuel ratio is used as a basis of separation.

From a physical standpoint all coals are first divided into those
of compact texture and those of woody, fibrous, or earthy texture.
Those of compact texture are next divided into an anthracite class
and a bitumite class. The anthracite class has a fuel ratio of 7+ and

120 THE CLASSIFICATION OF COALS

a non-luminous flame, and the bitumite class a fuel ratio of less than
7 and a luminous flame. The latter class includes the bituminous
and subbituminous coals.

The anthracites are further divided into true, hard anthracites with
conchoidal fracture, high specific gravity and submetallic luster
and the soft anthracites with semi-cubic fracture and low specific
gravity such as the so-called anthracite at Bernice, Sullivan Co.,
Pa. The dividing line between these two groups is a fuel ratio of 10.

The bitumites are divided first into those with a B.t.u. value of
over 14,300 and those with a value less than that when calculated on
a coal free of moisture, ash and sulphur. The calculation is made
from the following formula:

B.t.u. (ash-, moisture-, B.t.u. (coal as received) 40 S.

sulphur-free) 100 (moisture + ash + sulphur)

The higher rank bitumites are divided into the Virginites, or so-called
smokeless coals, having a fuel ratio between 2.5 and 7, and those
with a fuel ratio below 2.5. The former have a short to medium flame
and the latter a long flame.

The Virginites are divided into three types having fuel ratios
respectively between 5 and 7; between 3.5 and 5; and between 2.5
and 3.5. The first type is a non-caking coal while the other two are
caking coals. The Pocahontas type has a fuel ratio of 3.5-5 and the
Sewell type a ratio of 2.5-3.5. The other group of the high grade
bitumites is divided into the caking or steam coals and the non-
caking or household coals. The caking, long-flamed coals are again
divided into two groups based on a fuel ratio of i .4. Those above this
figure are called the Pennsites from their abundance in Pennsylvania.
The Pennsites are again divided into Connellsite with a fuel ratio of
1.85 or more and Pittsite with a fuel ratio between 1.4 and 1.85.
These names are taken from the Connellsville and Pittsburgh dis-
tricts.

Those coals with a fuel ratio below 1.4 and a fixed-carbon-moisture
ratio of more than 6 are called Ohioites and those with a similar
fuel ratio but with the other ratio less than 6, but still in the bitumite
class, are called Illinoites. The Ohioites are again divided into the
Belmontites with a fixed-carbon-moisture ratio of more than 10
and Hockingites with a ratio between 6 and 10. The Illinoites which
are high-moisture coals are also subdivided.

ASHLEY'S USE CLASSIFICATION

121

The non-caking or household coals are divided into two groups,
the splintites and the cannellites, wh ch are separated on a physical
basis as their structure and fracture are quite different. The lower-
rank bituminous coals with a fuel value of less than 14,300 B.t.u.
on the ash-, moisture- and sulphur-free basis are divided into two
groups according to their weather resisting properties.

For the convenience of those persons who purchase coal by wire
Ashley has suggested letters to designate the various ranks of coal
and the grades in those ranks. The table of letter abbreviations for
the grades is as follows :

Ash per cent

Sulphur per cent

Fusibility of ash, degrees F.

VI = very low

0- 4

0.00-0.75

Less than 2200

/ = low

4- 8

0-75-1-5

2200-2400

m = medium

8-12

i-5 -2.5

2400-2600

h = high

I2-2O

2-5 -4

2600-2800

Vh = very high

2O+

4 +

2800+

The letters a, s, and / also stand for ash, sulphur and fusibility re-
spectively. The fusibility of the ash is an important factor in the
heating quality of the coal because of the effect it may have in clog-
ging the grates, and it should be given serious consideration.

This classification may appear complicated to the average man
dealing in coal; there will be many exceptions to the classes made and
people long accustomed to such terms as Pocahontas coal may at first
object to the use of Pocahontite for coal from another region; yet
there are a number of features in this classification wh'ch commend it.
One important one is the fact that a proximate analysis furnishes the
necessary data for making the computations

After a review of all available classifications of coal it must be con-
cluded that no one classification so far suggested meets with general
approval. Some of the classifications are very satisfactory in com-
bining the physical and chemical properties of certain of the coals so
that they coincide with the names familiar to the public, and firmly
established in the coal trade. Others are applicable to certain other
coals and it seems probable that when the number of analyses has
been greatly increased and our knowledge of the controlling chemical
factors in coals has become somewhat more advanced it will be possible
to formulate a classification which will be workable under most con-

122 THE CLASSIFICATION OF COALS

ditions at least. Some of the classifications may now be applied to
certain regions with satisfactory results, but it is improbable that any
one will ever be applicable to all kinds of coals from all districts,
owing to the great diversity of physical and chemical characters
resulting from the variations in the vegetal matter from which coals
have been derived and in the variable geological conditions under
which they have been developed. The classifications, therefore,
which require more than two factors as a basis for determination of
a type come nearer satisfying the fundamental requirements than
those which are based on a ratio between only two constituents, and
from a practical standpoint the making of ultimate analyses by the
present chemical methods is to be avoided when possible.

CHAPTER VI
THE ORIGIN OF COAL

Introduction

In the earlier days of geological science a few theorists, searching
for some abstruse explanation for the origin of coal seams suggested
that they were intruded into the enclosing strata as bituminous de-
posits of igneous origin in the same manner that sills of igneous rock
are injected between beds of sediments. Patrin regarded the seams
as extrusions of bituminous matter on the sea bottom. So definite
is the evidence, however, that all coal has resulted from the alteration
of vegetal matter in some form, that a theory of origin based on any
other premise may be dismissed without consideration. Any one
questioning this conclusion has but to observe the transition from
peat to lignite and from lignite to bituminous coal, with a gradual
decrease in the distinctness of the plant remains in passing from the
lower to the higher grades of coal, to be convinced regarding this
matter. Many of even the hard coal seams contain remnants of
trees completely changed to coal but retaining the markings of the
bark and other woody structures. The modern application of the
microscope to the study of those coals which show to the naked eye
no evidence of plant remains reveals the spores, the fragments of
resin and the modified woody tissue of the vegetation which formed
the coal.

Although it is almost universally agreed that all the varieties of
coal originated from vegetal matter there is much difference of opinion
regarding its mode of accumulation into such great bodies as those
which gave rise to the coal seams. There is also a great divergence
of opinion among geologists and paleobotanists regarding the proces-
ses by means of which the vegetation has been brought into the form
of brown coal, bituminous coal, or anthracite, in which it is now
found.

123

124 THE ORIGIN OF COAL

Theories for the Accumulation of the Vegetal Matter 1

There are two main theories for the accumulation of the vegetal
matter giving rise to coal seams, and there are two schools of geologists
supporting these theories. One school contends that the plant
remains accumulated in situ, that is, where the vegetation grew and
fell, and the deposit is said to be autochthonous in origin. The other
considers that the deposit is allochthonous , that it has accumulated as
a result of the transportation of the vegetal matter by water. Ac-
cording to the latter theory the fragments of plants have been carried
by streams and deposited on the bottom of the sea or in lakes, in
much the same manner as any other sediment would be carried, and
allowed to settle to the bottom to build up strata which later become
compressed into solid rock.

The evidence favoring the in situ or autochthonous origin of the
deposit may be summed up as follows: (i) There are large accumu-
lations of vegetal matter forming in swamps at the present time,
some of which are on a scale approaching those which gave rise to
coal seams of considerable extent. (2) The purity of the coal, or
its relative freedom from mineral matter, suggests the collection of
the vegetation in swamps rather than in deposits where it has been
transported with other sediments. The periods of high water when
the greatest amount of vegetation is transported are also those when
most mineral matter is carried. (3) Numerous tree trunks with
their roots firmly embedded in the underlying clays occur in the coal
seams and in some cases the rootlets pierce fragments of buried wood
in the clays. (4) The topographic conditions under which the large
coal fields formed were like that of a land surface near the critical level
(that is, near sea level), and a slight sinking of the land would permit
the sea to transgress over it or, in basins removed from the sea, per-
mit sediment to be washed into the basin from adjoining lands.
(5) Old soils on which the trees grew lie beneath the seams in some
places. (6) Such an accumulation could not take place in the open
sea and estuaries are not in very favorable locations because of the
immense amount of mud usually carried into them. (7) The arrange-
ment of various portions of plants with respect to one another is not,
as a rule, that of transported material. (8) The lenses of cannel in

1 For summary of theories see "The formation of coal beds," by J. J. Stevenson.
Proc. Amer. Phil. Soc., Vol. 50, pp. 1-116, 1911.

THEORIES FOR ACCUMULATION OF VEGETAL MATTER 125

bituminous coal, or bands along the upper surface of bituminous coal
seams, indicate patches of open water in swamps where spores would
collect in great quantities rather than deposits forming part of an
ordinary sedimentary formation. (9) The lenses and bands of " min-
eral charcoal" suggest higher portions in the swamp exposed to weath-
ering and more extensive rotting than that undergone by the remainder
of the vegetation in the swamp. If this charcoal represents the
remnant of burned wood transported to open water as some have
suggested, it could scarcely have the distribution which it usually
has in the coal seams.

In favor of the transportation or allochthonous theory there are the
following factors: (i) Enormous quantities of timber are rafted
down streams in regions of virgin forest. (2) In some modern deltas
beds of peat and brown coal have been found. (3) Coal beds are
often associated with marine fossils which occur in the strata im-
mediately above or below the seams of coal. (4) The rocks associ-
ated with the coal are distinctly sedimentary and the seams appear
to constitute a part of a regular sedimentary series, usually showing
an increasing fineness in the particles of sediment in the rocks under-
lying the seam as the seam is approached. (5) The fire-clay beds
commonly found beneath coal seams are not necessarily clays on which
forests grew, as formerly supposed, because similar clays have been
found in marine formations unassociated with coal. (6) It is diffi-
cult to determine in many cases whether a stump of a tree is located
where it grew or whether it has been transported to its present lo-
cation and gradually buried by clay or sand which settled around it,
while resting upright on the bottom of the basin. (7) Trees have
been found with their tops headed downward. (8) The large num-
bers of spores grouped in the coal in some seams indicates their ability
to float about freely and collect in masses. (9) The presence of
fish remains in coal, especially the cannel coal of England, suggests
considerable open water where the vegetation accumulated. (10)
It would appear to be difficult for large trees to root in such an enor-
mous depth of vegetal matter as that necessary to produce some of
our thickest coal seams.

126 THE ORIGIN OF COAL

Historical Sketch of the Development of the Theories for the
Origin of Coal

As early as the year 1778 Buffon 1 recognized the vegetal origin of
coal and gave it the name charbon de terre, the term still frequently
used in France. In the same year Von Beroldingen 2 very intelli-
gently expounded the in situ origin of the vegetation in a peat-bog,
its burial and its transformation from peat into the various types
of coal. These writers were followed by many who had more or less
hazy and highly theoretical views regarding the origin of coal. Even
Darwin seemed to regard some of the coal beds as bituminous dis-
tillations from vegetal matter capable of migration from one rock
horizon to another.

In the year 1831 MacCulloch published a work 3 in which he sup-
ported the peat-to-coal theory. He pointed out that the plants
forming the peat were of terrestrial type and that they grew in swamps.
Three years later Marinnott recognized the prevalence of an under-
day with coal seams but stated that there could be no genetic con-
nection between the coal and the clay because he failed to find roots
in the clay. A little later Buckland 4 described how the vegetal mat-
ter was transported and he expounded the drift origin of the deposits.
Although Witham 5 had probably made the first microscopic studies
of coal in 1833 it remained for Link 6 to extend this work five years
later and apply his results to the origin of coal. He concluded that
coal was developed from peat because of the presence of various
vegetal materials in it and that the vegetation accumulated in place.
In 1841 Logan 7 stated that from his observations underclays were

1 Buffon, L. de., Histoire natureJle, generate et particuliere Sonnini Edn. Tome 9 me,
Paris.

2 Von Beroldingen, Franz., Beobachtungen, zweifel und Fragen, die Mineralogie
iiberhaupt und insbesondere ein natiirliches Mineral System betreffend; Erster Versuch,
i 77 8.

3 MacCulloch, J., A System of geology with a theory of the earth, Vol. II.

4 Buckland, W., Geology and mineralogy considered with reference to natural theology,
Phila. 1837.

5 Witham, H., On the Internal structure of fossil vegetables found in the carboniferous
and oolitic deposits of Great Britain, 1833.

6 Link, F., Uber den Ursprung der Steinkohlen und Braunkohlen nach mikroskopischen
Untersuchungen. Abhandlungen d. k. Preuss, Akad. Wiss. Berlin pp. 33-34, 1838.

7 Logan, W. E., On the character of the beds of clay lying immediately below the coal
seams of South Wales. Proc. Geol. Soc. London, Vol. Ill, 1841.

HISTORICAL SKETCH OF DEVELOPMENT OF THEORIES

characteristic of all coal seams and that from the presence of Stig-
maria in these clays the vegetation must have consisted chiefly of
this species which grew on these clays. Two years later Rogers 1
published a very comprehensive statement of the results of his ob-
servations. He concluded that the Pittsburgh seam extends over
at least 14,000 square miles and that when isolated areas where it
occurs are added the total area could not be far from 30,000 square
miles. He stated that he failed to see how beds of such extent and
purity could have been formed from drifted vegetation and he be-
lieved that they were formed in swamps on great marginal plains
subjected to gradual subsidence. He considered the underclays as
very common and Stigmaria as almost always present in them, often
preserving its fibrous processes. Another important point that he
brought out was that the roof was different from the sole formation
and that the roof sandstones showed evidence of strong currents.

From a study of Russian coals Murchison 2 favored the drift theory
but he also preferred the in situ theory for some of the English coal
seams where the underclays represent old soils on which Sigillaria
grew. Le Conte 3 favored the in situ theory because of the purity of
the coal and the preservation of the delicate portions of the vegetal
matter. He believed that the vegetation grew in bogs around the
mouths of large rivers. Jukes 4 favored the drift theory because of
the "rock faults" and frequent alternations of barren rock and coal.
He believed that the materials were sorted on the basis of specific
gravity. On the other hand Dawson concluded from a microscopic
study of coal and an extensive investigation of the South Joggins
area in Nova Scotia that the vegetation grew where it was accumul-
ated because of the numerous examples of standing trunks, and the
roots in place. He considered that the coal consisted chiefly of bark
and similar materials with spores as a very minor constituent. He
also regarded the irregularities in the floor of the seams as charac-
teristic of the inequalities seen in swamps of the present day. Steven-

1 Rogers, H. D., An inquiry into the origin of the appalachian coal strata, bituminous
and anthracite, Repts. of Amer. Ass. of Geologists and Naturalists, Boston, 1843.

2 Murchison, R. I., The geology of Russia in Europe and the Ural Mountains, Vol.
I, p. 112, 1845.

3 Le Conte, J., Lectures on coal. Ann. Rept, Smithsonian Inst., p. 131, 1858.

4 Jukes, J. B., The South Staffordshire coal field. Memoirs Geol. Survey of Great
Britain, 2 ed. London 1859.

128 THE ORIGIN OF COAL

son, 1 Andrews, 2 and Newberry, 3 as a result of their studies in Penn-
sylvania, Ohio and West Virginia strongly support the in situ theory.
Dana considered that the coal was made up of all parts of the trees
and that it accumulated in marshes. Mietzsch 4 was opposed to the
transport theory and described the sunken forests near the coast off
Rotterdam as illustrative of buried peat deposits found in situ. In
1878 Lesley 5 described how cannel lenses occur in pools on the mass of
vegetation which formed the coal seam and pointed out the significant
fact that if the coal deposits were not formed in a continuously sub-
siding area it would have been impossible for the many thousands of
feet of shallow water deposits filling the Appalachian trough to have
been laid down beneath the Coal Measures. He also believed that
the underclays represented the finer particles of rock sorted out of
the coarse sandstones and conglomerates and concluded that where
underclays were thick they should therefore be associated with ex-
tensive sandstone strata. Grand' Eury 6 seems to have favored a
sort of combined in situ and drift theory as he believed the vegetation
collected, suffered considerable decomposition, and was then washed
from the land into the standing water where it was buried. He
regarded the mineral charcoal as wood dried in the air. An objection
was raised to the in situ theory because the roots of the trees do not
penetrate the coal but spread out over it at the top of the seam in-
dicating that they cannot exist in a mass of decomposing vegetal
matter. It is well known, however, that this objection is overcome
by observation of a modern peat-bog or swamp. Griiner 7 objected
to the transportation of the vegetal matter chiefly because of the
freedom of the coal from mineral sediment. He was strongly in
favor of accumulation in place.

In the year 1883 Von Gumbel 8 published an excellent discussion

1 Stevenson, J. J., The upper coal measures west of the Allegheny Mountains. Ann
Lye. Nat. Hist. N. Y., Vol. X, p. 226, 1873.

Andrews, E. B., Geol. Survey of Ohio. Vol. I, Pt. I, 1873.

Newberry, J. S., Geol. Survey of Ohio, Vol. II, Pt. I, 1874.

Mietzsch, H., Geologic der Kohlenlager, 1875.

Lesley, J. P., Second Geol. Survey of Pa., 1878.

Grand'Eury, Memoire sur la formation de la houille. Ann. des Mines Ser. 8, Tome
I, 1882.

Griiner, L., Bassin houiller de la Loire, 1882.

Von Gumbel, C. W., Bertrage zur Kenntniss der Texturverhaltnisse der Mineral-
kohlen. Sitzungs d. Math. Phys. Klasse k. b. Akad. Wiss., Vol. 13, p. 113, 1883.

HISTORICAL SKETCH OF DEVELOPMENT OF THEORIES 1 29

of his microscopic and field observations. He treated fragments of
coal with potassium chlorate, nitric acid and later with ammonia.
He then washed them with absolute alcohol, thus employing a system
very similar to that used in recent years. He showed that even the
" stove" coal is made up of the various fragments of plant debris,
some of which are much more easily decomposed and much less dur-
able than others. He concluded that different varieties of coal may
result because of differences in the kinds or parts of plants, because
of differences in chemical and mechanical conditions, or in the ex-
ternal conditions during transformation. He first used the terms
allochthonous and autochthonous respectively to designate accumu-
lation by transportation and accumulation in place. He regarded
the interstratification of coal and distinct sediments as a strong
factor in favor of those who support the drift theory but he felt that
other evidence, especially the similarity between vegetation in
modern coastal swamps, subject to submergence by the sea, and the
peat deposits which gave rise to the coal, substantiated the autoch-
thonous origin of the coal.

As a champion of the drift theory probably no one man has pro-
duced more convincing evidence in its favor than has Fayol, 1 a mining
engineer, who made elaborate observations in the basin of Commentry
in central France. He further supported some of his conclusions by
laboratory experiments and as a result of his work a number of men
were led to accept his opinions, among them the well-known French
scientists, A. de Lapparent and B. Renault. He considered that the
vegetation grew on high lands surrounding a deep lake and was washed
into this body of water where it was deposited in a delta along with
sandstones and conglomerates. The distinct delta deposits, the
presence of abundant fish remains in associated shales, and the pres-
ence of trees with their tops headed downward are all taken as dis-
tinct evidences of the transportation of the vegetation. Many of
these arguments are successfully refuted by Stevenson 2 who later
studied the area and who claimed that nothing but a series of cloud-
bursts could tear the vegetation from the surrounding lands if it were
as dense as necessary to produce the coal seams under discussion in

1 Fayol, H., Terrain houiller de Commentry. Saint-Etienne. Livre Premier, Lithol-
ogie et Stratigraphie, 1887.

2 Stevenson, J. J., The Coal basin of Commentry in Central France. Ann. N. Y.
Acad. Sci. XIX, p. 161, 1910.

130 THE ORIGIN OF COAL

the 17,000 years postulated by Fayol for this operation. Stevenson
believed that the vegetation of this coal basin accumulated in situ.

Gresley 1 regarded coal as of drift origin and based his conclusions
largely upon observations in the Pittsburgh seam of the Appalachian
province. He claimed that there are two slate partings in this seam
from | to J inch thick separated by 3 to 4 inches of coal and occurring
over about 15,000 square miles. These contain no Stigmaria and the
underclay of this seam over large areas is a calcareous mud without
Stigmaria.

One of the strongest supporters of the in situ theory was Potonie. 2
He describes a core 750 meters long from the upper Silesian coal
measures in which there are at least 27 beds of coal each with an un-
derclay carrying Stigmaria. He also describes a fossil swamp in the
Miocene formations near Senftenberg which has given rise to .brown
coal and in which several generations of forests have grown and left
their stumps rooted in the vegetal matter. His valuable observations
on modern fresh-water swamps, such as those in Sumatra, have also
helped a great deal in clarifying our ideas on ancient peat-producing
swamps. He has suggested the following terms for organic deposits 3 :
Kaustobioliths, or combustible rocks of organic origin, which are
divided into Sapropelic deposits or those composed of animals and
aquatic plants such as cannel coal and oil shales; and humus deposits
which include all ordinary coals.

In reviewing the literature on the subject of the accumulation of
peat it is found that the majority of writers favor the autochthonous
or in situ theory, but there are many scientists of note who favor the
opposite view. Among living geologists the former theory is most
generally accepted and it is particularly well demonstrated in the
discussions of White 4 and his colleagues, although White accepts the
drift theory for some lesser deposits. On the other hand, Jeffrey, 5

1 Gresley, W. S., The slate binders of the Pittsburgh coal bed, Amer. Geologist, XIV,
p. 356, 1894.

2 Potoni6, H., Ueber Autochthonie von Carbonkohlen-Flotzen und des Senftenberger
Braunkohlen-Flotzes Jarb. d. k. Preuss. Geolog. Landesanstalt, 1895.

3 Potonie, H., Die Enstehung der Steinkohle und der.Kaustobiolithe iiberhaupt wie
des Torfes der Braunkohle des Petroleums u. s. w. 5th ed., 1910.

4 White, David, and Thiessen, R., The origin of coal. U. S. Bureau of Mines, Bull.
38, 1913-

6 Jeffrey, E. C, The mode of origin of coal. Jour, of Geol., Vol. XXIII, 1915, p. 218.
Also, Petrified coals and their bearing on the problem of the origin of coals. Proc. Nat.
Acad. Sciences, Vol. Ill, p. 206, 1917.

THE DEVELOPMENT OF PEAT

the paleobotanist as a result of his extensive microscopic studies
is a strong advocate of the drift theory, perhaps in a somewhat modi-
fied form. His conclusions are based very largely on the abundance
of spore remains, thus suggesting accumulation of the vegetal matter
in open water, as in cannel coal.

The writer believes that the majority of our coal seams are un-
doubtedly autochthonous in origin as most of the evidence supports
this theory. Owing, however, to the strong arguments advanced
and supported by both schools on this subject he agrees that some of
the less extensive deposits have been allocthonous, especially the
lens-shaped seams of limited extent occurring in lacustrine and estuar-
ine formations of the delta type.

Discussion of the Theories of the Origin of Coal

(1) The development of peat in bogs, marshes, and swamps. Peat-
bogs. At the present day a vast amount of peat is being formed in
small lakes and bogs, particularly in the cooler, wet climates and in

;

FIG. 18. Diagram illustrating the formation of peat in a bog and the
extension of the larger trees over the peat deposit.

the regions which have been glaciated and where drainage is there-
fore poor. 1 The depth of the peat may vary from a few inches to
50 feet but the detached areas covered by it are comparatively small
and while a peat-bog may serve to demonstrate how vegetal matter
accumulates in considerable quantities it is in no way comparable in
extent to the great bodies of vegetation which must have given rise
to our important coal seams. These peat-bogs generally begin with
a pond or a small lake varying from a few hundred feet up to a mile
or more in diameter. The development of the peat begins with the
growth and partial decay of a fringe of plants around the border of
1 Davis, C. A., The origin of peat. U. S. Bur. of Mines, Bull. 38, pp. 165-186, 1913.

132 THE ORIGIN OF COAL

the lake. The first plants to develop are usually the pond weeds and
water lilies. These are followed by the bulrushes and beyond them
the floating algae live in the deeper water where they do not reach
the bottom. As this vegetation grows and dies, season after season,
a deposit of peat develops along the shore and as it grows higher the
plants mentioned gradually shift their relative position farther out
from the shore and toward the center of the lake (Fig. 18). In the
course of time a growth of sphagnum or "peat-moss," a large grayish-
green or whitish moss, extends outwards over the peat deposit and
this is followed by small trees of several species, chiefly the conifers;
including the tamarack and spruce. As the peat becomes more and
more firm, larger and larger trees will be supported and deciduous
trees such as the white birch may partially replace the conifers. In
time the lake may be completely filled up and the area overgrown by
small timber.

As the peat develops several zones may be observed in the deposit.
A very dark, heavy, dense peat forms at the bottom and lighter-
colored, more fibrous layers occur as the surface is approached. Scat-
tered through these layers there may be trunks of trees more or less
altered. These trees grew around the border of the lake and were
killed at times of high water, or they may have been blown down or
otherwise killed and they then became imbedded in the peat. In
seasons when the water is low and the surface of the bog stands above
the water-soaked level the vegetation may suffer considerably more
decomposition, or dry rot, than in other seasons and all but the more
resistant portions of the material will be destroyed. This may, if
carried sufficiently far, give rise to mineral charcoal. In wet seasons
when the water is high, a much smaller degree of decomposition occurs
and a much greater proportion of the vegetation is preserved so that
alternate bands with varying composition result.

Marshes: In addition to the peat bogs there are in various parts
of the world large areas without trees, where peat forms a shallow
deposit covering a water-soaked land surface, but where standing
water is not usually present except in the wet seasons. These areas
are found chiefly in the frigid and terhperate zone, but they may also
be found in the tropics. In the colder regions the peat consists mostly
of sphagnum, but in some places rushes and grasses may form a con-
siderable part of the plant growth. The Arctic tundra is one type of

THE DEVELOPMENT OF PEAT

133

such deposit. In the warmer climates cane-brakes and "tuie"
marshes represent this type of peat development.

Fresh-water swamps: Interesting as the peat bogs and marshes
may be in illustrating various ways in which peat may develop, they
cannot be regarded as the sources of the peat which gave rise to im-

FIG. 19. Cowhouse Run, Okefinokee Swamp, Ga.
(Photo by Francis Harper.)

portant deposits of coal. There is sufficient peat in the temperate
regions of the world today to form large amounts of coal, if it were
concentrated into coal seams, but no single bog or marsh known would
supply sufficient peat to make a large coal seam, although Geikie
states that one-seventh of Ireland is covered with peat bogs and in
Allen alone, 238,500 acres are covered with peat to an average depth
of 25 feet.

There are, however, other deposits of peat forming at the present
day in both temperate and tropical regions, which much more nearly

134

THE ORIGIN OF COAL

represent the kind of accumulation of vegetation which gave rise to
extensive coal seams. These deposits are forming in immense fresh-
water swamps such as the Dismal Swamp of North Carolina and
Virginia and the Sumatra swamp in the East Indies. Large swamps
of similar character are believed to exist in tropical Africa and South
America. From descriptions of these swamps it is apparent that the
idea so commonly held that peat can scarcely form in warm climates
and that modern deposits of peat are practically restricted to the

FIG. 20. Scene in a cypress bay, Okefinokee Swamp, Ga
(Photo by Francis Harper.)

cooler regions of the earth is not correct. In fact there are deposits
of peat in these swamps much more nearly approaching large coal
seams in extent than anything found in the cooler regions. If there
be an abundant rainfall on poorly drained land and a type of vege-
tation capable of very rapid growth, the wastage of peat due to higher

THE DEVELOPMENT OF PEAT

135

temperature may be offset by the greater rate of growth in tropical
or sub-tropical climates.

According to Shaler 1 the inundated portion of the Dismal Swamp
is about 38 miles north and south by 25 miles east and west. The

FIG. 21. Map of the Dismal Swamp. North Carolina and Virginia, showing
the relation of the swamp to the coastal plain. (After Shaler, U. S. Geol. Survey.)

swamp which was apparently extending its borders before man began
to drain and cultivate portions of it is now considerably smaller than

1 Shaler, N. S., Geology of the Dismal Swamp District of Virginia and North Carolina.
U. S. Geol. Survey, Tenth Ann. Kept., Pt. i, pp. 313-339, 1888-9.

136 THE ORIGIN OF COAL

it was originally. Osbon places the total area of this swamp originally
at 2200 square miles with 700 now drained. 1 It lies on the coastal
plain and represents the largest continuous swamp area of the many
scattered over this plain between the Appalachian Mountains and the
sea (Fig. 21). The rocks underlying the swamp are mostly strati-
fied marine sands with some lime beds probably of Pliocene age. The
surface is slightly rolling or billowy but the differences in elevation
are small and on the whole the area approaches a level surface from
5 to 25 feet above the sea. The geological events which have given
rise to the present relief are outlined by Shaler as follows: (i) A
subsidence leading to the formation of the Pliocene plateau. (2)
Elevation permitting erosion of the plateau. (3) Subsidence permit-
ting deposition of non-fossiliferous sands. (4) Elevation permitting
carving of surface. (5) Subsidence and formation of the Nansemond
escarpment. (6) Reelevation and development of valleys of streams
to present depth. (7) Sinking now taking place.

From this description it is seen that this swamp stands near the
critical level in much the same way as the swamps of the coal measures
must have been situated and that a slight change in elevation might
produce dry land or a transgression of the sea. There are areas of
open water in this swamp, such as Lake Drummond, which might
represent the more extensive areas of open water in the coal measure
swamps in which the spores collect and produce canneloid, thus
giving rise to lenses of cannel coal. This lake is gradually filling up
with peat by the encroachment of the vegetation. There are other
areas which are never completely submerged and which are compara-
tively dry during the greater part of the dry seasons. These exposed
areas would illustrate those on which mineral charcoal would form
because of more extensive rotting resulting from exposure (Fig. 22).

The vegetation in this swamp varies with the amount of water
present. The higher levels are usually occupied by pines such as the
common southern pine. The lower levels are mainly occupied by
three species of trees, the Taxodium, or bald cypress, the juniper,
and the black gum. The juniper occurs on the land which becomes
fairly well dried during the dry season. The other two may grow in
areas continuously covered with water if the water does not rise too

1 Osbon, C. C., Peat in the Dismal Swamp, Virginia and North Carolina. U. S.
Geol. Survey, Bull. yn-C, 1919.

THE DEVELOPMENT OF PEAT

137

high, as they develop knees, or arched roots to aid in keeping them-
selves above water.

The fallen trees, the spores, the leaves, and other plant debris are
continually falling into the water in this swamp and building up a
layer of peat which has been estimated at i to 20 feet in thickness.
Osbon has estimated that 1500 square miles are covered to an average

FIG. 22. Lake Drummond, Dismal Swamp.
Geol. Survey.)

(Photo by Shaler, U. S.

depth of 7 feet and that the total available peat in this swamp is about
672,000,000 tons. This peat if turned to coal would be sufficient to
form a seam from about i inch to 20 inches in thickness and it would
have many of the characteristics of coal seams as we are familiar with
them today. The ash content is quite satisfactory. If the sinking
of this area continued very slowly, the living vegetation would be
destroyed and opportunities would be offered for the collection and
preservation of a large amount of vegetation. It might become
buried by the encroachment of the sea and the deposition of sediments
over the vegetation. Submerged stumps in the valley of the Pamlico
River, in this area, indicate that in comparatively recent time, geol-

138 THE ORIGIN OF COAL

ogically speaking, submergence has occurred. On the other hand a
slight uplift of the land surrounding this basin might cause large
quantities of mud, sand, or gravel to be washed into the swamp and
form partings in the resulting coal when a new swamp formed on top
of this rock.

The other large fresh-water swamp of which we have some definite
knowledge is one on the island of Sumatra described by Potonie. 1
It is said to cover about 312 square miles. The peat deposit reaches
a thickness of 9 meters or nearly 30 feet in this swamp and it is made
up of a mixture of logs and plant debris of all sorts. There is a stag-
nant, tea-colored blanket of fresh-water over the peat, which makes
an efficient preserving fluid for the materials which fall into it. The
ash content of the dried peat is 6.39 per cent. This material if com-
pressed into bituminous coal should produce a seam nearly 3 feet
thick, as the lower layers of peat have already undergone considerable
change and they are dense and compact.

That many swamps and forests have become buried beneath mar-
ine and fresh- water deposits is well demonstrated by Stevenson 2 in
his article on " Buried Forests." An interesting example is also
mentioned by Mietzsch 3 who says that off Rotterdam two bogs,
5 meters and 6 meters thick, are separated by a bed of clay 4 meters
in thickness. Some of the trees are still standing and they are of
types which inhabited the adjacent lands centuries ago. Another
of greater antiquity was described by Potonie from the Miocene and
previously mentioned in this chapter. In these illustrations we seem
to have abundant evidence of the efficacy of fresh-water swamps in
producing coal deposits under proper climatic and topographic con-
ditions.

Mangrove swamps: There are also certain salt and brackish water
swamps, which occur along the sea coasts and in which the trees are
mostly mangroves. They are known as mangrove swamps. These
are found in the tropical or semi-tropical regions and some of them
are of considerable extent. They may be seen in northern New
Zealand, Ceylon, Cuba, Florida, and many other countries (Fig. 26).

1 Potonie, H., Die Entstehung der Steinkohle und der Kaustobiolithe iiberhaupt,
5th ed., pp. 152-160, 1910.

2 Stevenson, J. J., The formation of coal beds, Pt. II, Proc. Amer. Phil. Soc., Vol. 50,
p. 626, 1911.

3 Loc. cit.

DRIFTED VEGETATION AND DELTA DEPOSITS

139

The long stilt-like roots raise the trunk above the water and among
these roots the vegetal debris collects. They sometimes extend a
short distance from the shore where the water is shallow and while
considerable peat forms in such a swamp, so far as the writer's ob-
servations go, there is always a large amount of sand mixed with the
peat owing to the tidal currents and storm-waves which wash it into
the swamp. This type of swamp never seemed very favorable for

FIG. 23. Portion of Dismal Swamp in which peat is covered with water. (Photo by
Shaler, U. S. Geol. Survey.)

the formation of extensive bodies of peat. These trees may, however,
grow farther back from the sea and even in fresh-water swamps where
conditions are more favorable to the formation of purer peat deposits.
(2) Drifted vegetation and delta deposits. The drift theory for
the collection of vegetation giving rise to coal deposits has many sup-
porters who naturally invoke processes now operative on the earth's
surface to substantiate their arguments. They can point to a few
cases where coal is being formed or has been formed in undoubted
delta deposits in comparatively recent time considered from the

140 THE ORIGIN OF COAL

geological standpoint. In an article describing briefly the artesian
wells at Venice, Italy, Degousee 1 mentions lignite beds which were
pierced in drilling for water. He states that the sea is very shallow
in the Gulf of Venice for a long distance from the shore At a depth
of 60 to 70 meters and above the real artesian bed ascending water is
struck which is so charged with hydrogen carbide that the water is
intermittently thrown above the surface with great violence. This
gas is said to burn well but nothing is recorded regarding its relation
to the lignite beds, fn all the wells bored several beds of lignite in
sand and clay were passed through. Unfortunately we have no de-
tailed data concerning the thickness or number of these seams. There
were in the lignite fragments of wood sufficiently preserved to be
identified.

Reference is frequently made in literature to the enormous amount
of timber floating down the Mississippi River and the rafts of drift-
wood, several miles in length, which years ago blocked the channel
of the stream. Conditions as they are at present, in the cleared and
cultivated valley of that river, make, however, a poor parallel to the
conditions prevailing when the country was covered with virgin forest,
as a vastly greater proportion of mineral matter is being carried than
would have been carried then. A closer parallel to the conditions
prevailing when coal was being formed may possibly be seen in some
of the rivers in northern Canada where many streams flow through
regions covered with virgin forests and peat bogs. One is impressed,
for example, by the vast quantities of timber which descend the
streams to James Bay every spring (Fig. 27). Owing, however, to
the great variation in size of the fragments and the difference in the
rate at which they become water-logged and sink, or float out to sea,
there seems little opportunity for this material to collect into any
extensive bodies of peat on the sea bottom. One of the main diffi-
culties in the way of its producing coal is the fact that when most
plant debris is carried in flood periods there is always more than the
normal quota of mineral matter taken along.

In an effort to obtain definite information regarding the proportion
of plant debris carried by streams and thus support his arguments

1 Degousee, M. J., Note sur les alluvions formant les lagunes venitiennes, et sur les
puits artesiens de la ville de Venise. Bull, de la Societe Geologique 2 Serie, Tome 8,
pp. 481-4, 1850.

DRIFTED VEGETATION AND DELTA DEPOSITS

141

for the drift theory for the basin of Commentry, central France,
Fayol 1 stretched a wire screen of one centimeter mesh across a stream
known as the Baune. This was done in the month of January and
it collected 502 grams in 2 minutes, or 1.5 grams for each cubic meter
of water passed through. He also made certain laboratory exper-
iments in a small body of water to determine the action of vegetal
matter in sinking to the bottom and of mixing, or separating itself

FIG. 24. Timber undergoing partial decay in the Dismal Swamp. (Photo by Shaler,

U. S. Geol. Survey.)

from the sediment which was carried into the body of standing water
with the plant materials. He found that the roots were among the
first materials to sink. Many stems remained in an upright or in-
clined position on the bottom and the plant debris formed deposits
varying from practically pure vegetal matter to those highly mixed
with mineral matter.
According to this writer, the basin at Commentry, in Carboniferous

1 Fayol, Henri. Terraine houiller de Commentry, Livre Premier, fitudes sur le terrain
houiller de Commentry, p. 397, 1887.

142

THE ORIGIN OF COAL

time was occupied by a fresh-water lake surrounded by high lands.
Streams entered the lake with sufficient gradient to move large
boulders, some of granite in the conglomerate underlying the coal
reaching a cubic meter in volume and suggesting for them a glacial
origin. As a parting in the famous Grande Couche, a seam reaching
a maximum thickness of 20 meters, there are 8 meters of conglomerate
with some boulders half a meter in diameter. Another peculiar

=5*44-

FIG. 25. Destruction of trees by high water in the Dismal Swamp. (Photo by
Shaler, U. S. Geol. Survey.)

feature of these coal deposits is the presence in the conglomerates of
the Coal Measures of pebbles of coal and abundant grains of coal
in the sandstones showing that older coal beds had been broken up
by erosion.

Some of the other evidences of the drift origin of the coal at Com-
mentry are trees with their trunks in an inverted position, and the
presence of abundant fossil fish in the associated rocks. The occur-
rence of inverted tree trunks cannot, however, always be regarded as
conclusive evidence of drift origin because one may often see trees in
a swamp broken off by the wind and embedded, head down, in the

DRIFTED VEGETATION AND DELTA DEPOSITS 143

peat. Their chances for preservation are, however, not great unless
covered with clay or sand, since most of them project above the water-
level. The presence of upright trunks and stumps on the other hand
cannot be regarded in many cases as definite evidence of growth in
place because a stump floating into a body of water will most likely
settle to the bottom in an upright position, owing to the weight of the
roots if they be present, or the greater weight of the big end of the
trunk, when water-logged, if roots be absent. There are stumps
in the Coal Measures at St. fitienne, France, with a number of roots
penetrating the underlying rocks but it is impossible to determine
whether the stumps are in place or whether they floated to their
present position and became buried by sediment (Fig. 28) . If, how-
ever, the unbroken rootlets are found in their proper position and
roots are found piercing fragments of buried wood this would be
regarded as proof of their growth in situ. Such conditions are found
in many of the great coal fields.

Some writers attach importance to the relative number of upright
stumps and trunks in the coal and in the adjacent conglomerates,
sandstones, and shales. This circumstance cannot carry any par-
ticular weight in the argument because it is evident that these rocks
are capable of supporting the trunks in this upright position and
they were buried quickly; whereas the soft, yielding peat would
permit them to be easily crushed down flat by the superincumbent
load of rock or vegetal matter. Fayol observed that in the Commentry
basin 99.5 per cent of the stems were flat in the coal and 0.5 per cent
vertical or inclined. In the sandstones 70 per cent were flat and in
the conglomerates 60 per cent.

The fact that so much better plant remains are found in the shales
and " coal balls" than in the coal itself is due to the soft, pliable peat,
which gave rise to the coal, squeezing and creeping under the weight
of the overlying rocks and to partial decomposition of the vegetal
matter because of longer exposure destroying original structures.
In many cases the tree will rot out in the sandstone or shale leaving
perhaps traces of the bark and this space becomes filled later by sand
or clay which is squeezed into it, thus giving a stone-cast of the tree.
The rock in these casts often differs from the rock surrounding
them because it has been squeezed up from a lower stratum
or down from a higher stratum than the one holding the cast. In

144

THE ORIGIN OF COAL

some of these casts, mineral matter from solution may be deposited
where the wood has disappeared, giving more iron oxide, calcium car-
bonate or similar mineral than is found in the surrounding rock.

The sequence of conglomerate, sandstone, shale, and coal beds in
varying succession argues strongly for the drift theory as it would
appear that in so many cases there was almost complete assortment
of sediments on the basis of specific gravity and rate of settling.
Further, the accumulation of vegetation to such a tremendous depth

iii

FIG. 26. Mangrove swamp creeping out over the sea on coast of New Zealand.
(Photo by E. S. Moore.)

as that necessary to produce 50 or 60 feet of anthracite might seem to
some most easily accounted for by supposing that the material was
transported and dumped into a body of water because there would
be little opportunity for trees growing in this mass to root in anything
but peat. It has been shown, however, that many of the larger trees
which occupied the swamps were specially equipped with roots
adapted to an existence near the surface of wet peat deposits and they
were no doubt supported by the extensive matting together and inter-
locking of the roots of the forest trees. It is known that trees of
considerable size can subsist at the present day on thick deposits of
peat and it seems much easier to explain the accumulation of such
great masses of peat, so free from mineral matter and requiring such

DRIFTED VEGETATION AND DELTA DEPOSITS 145

long periods to form, in a swamp free from sediment than in open
water where every season large quantities of mud or silt are likely to
be carried and spread over it during floods.

The Sargasso Sea: 1 One other phase of the drift theory may be
mentioned. It has been suggested that the great mass of plankton
floating on the ocean might segregate in the eddies in the ocean cur-
rents and, sinking to the bottom, build up peat deposits which would
be well preserved. This mass would be made up of great quantities

FIG. 27. Drifted timber along the Metagami River, James Bay basin, Canada.

(Photo by E. S. Moore.)

of very small, low types of floating plants associated with sea-weed
and other forms of plant life which would be carried about on the
ocean surface. While it is true that some material is collecting in
this way at the present time anyone familiar with ocean travel knows
that coal beds were never formed in this way because there is not
sufficient material being deposited. Deep-sea dredgings have failed
to show any accumulation of plant material worth mentioning. Other
convincing evidence opposing this theory is the presence of coarse
littoral sediments so frequently interbedded with the coal seams, in-
dicating that these sediments are shallow water or land formations
and not deep-sea deposits.

1 Mohr, F., Geschichte der Erde, 1886.

146 THE ORIGIN OF COAL

Rate at which Peat Accumulates

The rate at which peat forms in any given region will depend upon
the rate of growth and proportional rate of decay. The nature of
the vegetation will have a great influence on the rate of growth as
some trees grow so much faster than others on an area partially or
entirely covered with water, the condition essential for the preser-
vation of the vegetation after it is grown. Coarse vegetation will
naturally build faster than fine material but there are certain types
of the finer plant debris which build at a fairly rapid rate owing to the
fact that the proportional shrinkage is not so great as in the coarse
debris and the material is being supplied to the bog every year. If
we consider for example the spores of plants which fall every spring
and float about in the open bodies of water until they sink we will
find that a large amount of this material collects every year and goes
to build up canneloid, which later forms cannel coal. The writer has
seen, while traveling in the late spring through the northern woods
of this continent, such quantities of spores and pollen grains from the
birch, poplar, and related trees floating on the water of the small lakes
and ponds that it was impossible to obtain water fit to drink. There
are often so many of these green globules in the water that in places
it becomes thick with them. They collect in bands and little ridges
along the shore where washed up by the waves. It can be easily under-
stood how vast quantities of these spores collecting in patches of
open water in large swamps might produce lenses of cannel with the
other coal. Modern microscopic investigations of coal tend to show
that spores are very widely distributed through all coal and that owing
to their resistance to decay they form a prominent constituent of the
coal. Another constituent which resists decay and is prominent
in many coals, especially those formed chiefly from coniferous trees,
is resin. This has been observed in considerable proportions in micro-
scopic studies.

The soil will have some influence but after a thick layer of peat
has developed the plants gather most of their sustenance from the
air and water. It seems probable that the feldspathic rocks ob-
served as so common in coal measures in various countries of the world
may have furnished more than the average amount of potash to the
vegetation, which was able to root in the soils of those days, and thus
produced conditions favorable for growth.

RATE AT WHICH PEAT ACCUMULATES 147

The climate plays a large role in the deposition of peat because a
wet, uniform climate will produce much more vegetation in a given
time, other things being equal, than a climate where growth and pres-
ervation are limited to certain seasons of the year. The rate of de-
cay in a warm climate will be greater but this is largely offset by a
good water blanket for the fallen plants. The latter is possible only
if the climate be uniformly wet throughout the year. If there be
long, alternately wet and dry seasons, there will be little peat formed,
unless the climate be cool, no matter how much rain falls.

There is no satisfactory way of computing the rate at which peat
accumulated in the coal-forming periods. We can only judge the
rate approximately by considering the amount of peat which forms
at the present day in a given time and it is only in a few areas that
definite information can be obtained regarding the rate of formation
of modern peat deposits. Where a forest is cut away or where peat
grows over a road or other cultural feature whose age is known,
quite accurate data may be obtained regarding its growth. Lesquer-
eaux considers that in the Jura of Switzerland, peat has formed to a
depth of 1 8 to 20 inches on an area which has been cut over within
50 years. Geikie 1 gives quite a number of cases where the rate of
growth is well established. In the valley of the Somme, 3 feet of
peat has developed in 30 to 40 years, and on a moor in Hanover 4
to 6 feet has grown in about 30 years. Near Lake Constance a layer
3 to 4 feet thick has required only 24 years while among the Danish
mosses 10 feet required 250 to 300 years for its deposition.

In summing up the data concerning the rate of growth of peat
Ashley 2 states that under the most favorable conditions i foot may
form in 5 years, and that i foot in 10 years is a fair average maximum.
In the larger and deeper basins the rate is slower and in any case the
newly formed peat soon contracts to only a fraction of its original
bulk. Lesquereaux considers that a foot of peat at the surface
shrinks to f foot at depth in the bog. By taking into account the
specific gravity of the peat at the surface and at depth, it is possible
to arrive at an approximate figure for the amount of old peat formed
from the surface layer. It is generally agreed that approximately

1 Geikie, A., Text-book of geology, 2nd ed., p. 443, 1885.

2 Ashley, G. H., The maximum rate of the deposition of coal. Econ. Geol. Vol. 2,
PP- 34-47, 1907-

148 THE ORIGIN OF COAL

i foot per century is a fair average rate for the development of old
compressed peat.

The Amount of Coal Derived from a Given Amount of Peat

Having considered the rate at which peat forms we may take up
the question of the approximate rate of the formation of coal. No
definite figures can be obtained on this subject but a number of val-
uable observations have been made. Renault 1 has decided after ob-

FIG. 28. Upright trunk in Coal Measures at St. Etienne, France. Broken at base.
(Photo by E. S. Moore.)

serving carefully the shrinkage of stems of trees in passing from wood
to coal that the loss is from eleven-twelfths to twenty-nine-thirtieths
of the original. This is for the change to bituminous coal of the
Commentry basin in France. Ashley 2 from calculations made on
the relative specific gravity, and on the loss of moisture and other
constituents, concludes that 3 feet of old peat would form i foot of
bituminous coal such as that in the Pittsburgh seam, and, as a rule,
about 20 feet of vegetal matter will form i foot of coal. In deducing
his figures Ashley has also used other interesting examples such as the
shrinkage in the vegetal matter which formerly filled a small, deep
basin and now forms a thin lens-shaped layer of coal on the bot-

1 Renault, B., Sur quelques microorganisms des combustibles fossiles, Bull, de la Soc.
de 1'industrie min^rale, 3me serie Tome 13-14, 1899-190x5.

2 Ashley. Loc. cit., p. 42.

THE AMOUNT OF COAL DERIVED FROM PEAT 149

torn of the basin. He cites another case where two basins were
connected over a low ridge and, considering that the basins were
filled to a given level so that the peat could connect over the ridge,
an approximation may be reached regarding the relative amount of
coal formed on the ridge and in the basins from a mass of peat reach-
ing a given level.

If a foot of old, compact peat forms in a century and it requires
3 feet of this peat to form a foot of bituminous coal it will require
three centuries to form a foot of coal and three thousand years to
form a seam 10 feet thick.

Various attempts have been made to express the change from wood
to coal by chemical formulae but they are "unsatisfactory because the
formula given for cellulose will not represent the chemical composition
of all the material entering peat, and it is difficult to write a chemical
formula properly expressing the composition of a coal seam. There
is almost no end to the formulae which might be written. Renault 1
gives the following to illustrate the change from wood of Cordaites
to homogeneous coal:

(C 6 H 10 5 ) 4 = C 9 H 6 + 7 CH 4 + 8C0 2 + 3 H 2 O

Cellulose Bituminous Marsh gas Carbon dioxide Water
coal

Parr's formulae 2 for lignite and bituminous coal are:

(1) 5(C 6 H 10 5 ) = C 20 H 22 4 + 3CH 4 + 8H 2 O + 6CO 2 + CO

Cellulose Lignite Marsh gas Water Carbon Carbon

dioxide monoxide

(2) 6(C 6 H 10 5 ) = C 22 H 20 + 5CH 4 + ioH 2 O + 8CO 2 + CO

Bituminous
coal

These formulae are valuable in showing the relative proportions
of the various constituents of the wood which are supposed by these
investigators to be lost but they cannot be taken too literally as
representing the changes which have taken place.

1 Renault, Loc. cit., p. 299

2 Parr, S. W., Illinois Geol. Survey, Bull. 3, 1906.

THE ORIGIN OF COAL

The Topographic Conditions Prevailing During Coal-
forming Periods

On examining the topography of any of the continents as they
existed prior to and during the deposition of the vegetation giving rise
to the great coal deposits, it is found that extensive, low swampy
areas were very characteristic. The coal-forming periods invariably
followed periods when shallow, continental seas, which were gradually
filling: up, had spread over considerable areas of the continent. These

FIG. 29. Section at Treve, France showing numerous stumps in Coal Measures.

(After Grand 'Eury.)

seas gradually retreated leaving great expanses of low land, poorly
drained and ideal for the development of swamps on a large scale.
The conditions must have been closely parallel to those now found
on our great coastal plains along the Atlantic Ocean and the Gulf
of Mexico. In the eastern part of North America the deposition had
been predominantly marine previous to the Carboniferous period.
During this period the land over most of this part of the continent
began to emerge finally from the sea, never again to become an area
of extensive marine deposition, although the western portion of the
present continent continued to be covered with the sea. With the
emergence of this great area there was a differential rise of the area
bordering on the Atlantic and lying between the Atlantic as it then
existed, and a long northeast-southwest sound on its westward
side, known as the Appalachian trough. This trough was being filled
with sediments from the land masses forming Appalachia on the east,

TOPOGRAPHIC CONDITIONS DURING COAL-FORMING PERIODS 151

the pre-Cambrian areas to the north, and the Cincinnati arch to the
northwest. These land masses continued to be the source of clastic
sediments, for the area occupying the old Appalachian trough became
practically filled with sediments at the beginning of the Carboniferous
period, presenting the aspect of an extensive coastal plain. This
great flat area was subject to very gentle warpings, probably the
forerunners of the larger buckling movements which later produced
the Appalachian Mountains at the close of the coal-forming period.
This area was so near sea level that a slight rise brought it into the
condition of dry land or a small subsidence put it below the ocean
just as minor changes cause the Atlantic coastal plain of the present
day to rise above or fall below the sea.

In the larger of the depressions formed by warping of the strata
the swamps giving rise to the more extensive coal seams such, for
example, as the Pittsburgh seam originated. In many of the depres-
sions slow subsidence was constantly going on as these basins were
being filled up with vegetal matter and sediment but it seems probable
that the conditions can be best accounted for by frequent small
elevations of the surrounding land and consequent relative sinking
of the low areas. In some cases the conditions even permitted en-
croachment of the sea, the destruction of forests, and the deposition
of limestones and other marine deposits over the accumulated vegetal
matter. Much of the sediment found associated with coal seams
consists of feldspathic sands indicating incomplete decomposition, as
if the materials composing the rock had been swept off a land surface
where rocks were disintegrating. These products of disintegration
might have been carried off to the basins owing to change of climate,
or elevation of the land on which they were lying, causing greater
activity of water. These materials could be derived from the dis-
integration of granitic rocks and they could be rapidly transported
to an area of deposition without being completely sorted or water-
worn if streams became very active owing to increase in velocity due
to increase in gradient or volume of water.

The general absence of extensive erosional features in the measures
during Carboniferous time indicates that there was a general sub-
sidence in progress and that the swampy areas were seldom raised
sufficiently above the sea to permit much erosion of the formations
carrying the coal. They were areas of deposition rather than erosion.

152

THE ORIGIN OF COAL

The red beds of the later Permian indicate a drier climate than that
which had prevailed during the Carboniferous and the coal-forming
process had practically ceased when the larger movements producing
the Appalachian Mountains occurred.

An examination of the conditions in the western part of the con-
tinent at a later period shows that the conditions found in the east
during the Carboniferous, (Mississippian and Pennsylvanian) were

FIG. 30. Upright trunk in Coal Measures showing roots descending into rock to
right of the hammer. (Photo by E. S. Moore.)

practically duplicated in the west during the Jurassic and Cretaceous
periods. During the former period a large shallow sea extended over
the region now occupied by the Cretaceous and Tertiary coal deposits.
This sea gradually withdrew from the land and conditions became
favorable for extensive swamp development. The coal-forming proc-
esses ended with the elevation of the Rocky Mountains as it did in the
east with the rise of the Appalachians. An examination of other
continents will reveal a similar close relation between the topographic
conditions and the development of extensive coal-bearing formations.
The essential features are base-leveling of the higher areas with a
consequent aggrading and leveling up of the lower ones, and a general
slow subsidence of the areas of peat deposition.

THE ORIGIN OF UNDERCLAYS 153

The Origin of Underclays

Various names have been applied to the clays underlying coal
seams such as the "sole," "seatearth," and "mur." Some seams
have no distinct underclay and some even lie on granite, schist or
other igneous or metamorphic rocks. Beneath others the floor of
the seam is conglomerate or coarse sandstone, and limestone under-
lies a few beds. In many seams the change from coal to barren rock
is abrupt while in others there is carbonaceous shale or black slate
lying next to the coal indicating a gradual transition from the coal
to the rocks free from vegetal matter. The shales, being less porous,
are more likely to have partly preserved vegetation in them than the
sandstones are, because the latter permit access of oxidizing water
which decomposes the vegetal matter and leaves no carbonaceous
deposit. The change thus appears more abrupt at the contact with
sandstone than it really was.

Underclays are so abundant in certain coal fields that some early
writers, like Logan, regarded them as a universal accompaniment of
coal seams. They are almost everywhere present under the seams of
some of the English and American fields of Carboniferous age and
they have been regarded by some writers as inseparably connected
genetically with the seams. Many of these clays are fireclays and
they are of great economic importance. They seldom show good
stratification which may be at least partly explained by their plastic
property, permitting them to be squeezed and kneaded under pressure
until the bedding was lost. It is also observed that a layer of rock
which has been penetrated by innumerable roots usually loses its
laminated character.

The unstratified character, the bleached appearance, and the
common occurrence of Stigmaria, or roots in these clays has led many
observers to regard them as old soils on which the vegetation forming
the coal seams grew. It is well known from observation that the
roots of plants will bleach the rocks they penetrate and these under-
clays bear a certain resemblance to the muds under some modern
peat-bogs and swamps. It is also well known, however, that modern
peat does not grow only on such soils but it may be found on sands,
marls, or almost any kind of rock. It is therefore evident that under-
clays are not essential to the growth of luxuriant vegetation and the
question may then be asked whether the vegetation is essential to

154 THE ORIGIN OF COAL

the development of the underclays. Some writers have gone so far
as to claim that where coal is not found above the fireclay it has been
removed by erosion, but such a sweeping statement does not seem to
be justified because fireclays have been found in marine deposits
unassociated with coal deposits of any kind. Most of those clays
are, however, stratified and laminated.

If the drift theory were to be accepted for the accumulation of the
vegetal matter these clays should represent a deposit of the finest
and most completely assorted mineral sediment deposited in quiet
water just before the lighter vegetal matter settled to the bottom.
In that case, however, they should show more stratification than
they do. Arber 1 suggests that they are marine and brackish water
oozes deposited in estuaries like the black oozes of the nipa and man-
grove swamps of the present day. If this be so, it is hard to under-
stand why they are found only in their present position with reference
to the coal. If coal be deposited in accordance with the in situ theory
then these clays may have been the finer material which filled the
basin in which the swamp occurred and the lack of stratification re-
sulted from the growth of the plants upon it and later movements in
a semi-plastic mass.

There is one other possibility. If the statement of Mietzsch holds
good that living Lycopodiaceae have from 22 to 26 per cent of clayey
matter in their ash and the ancient types of these plants had a similar
proportion, may not the decay of vast quantities of such plants on
the floor of a swamp, before there was sufficient water over the vege-
tal matter to prevent decay, have produced a deposit such as the
underclay? Some efforts have been made to compare the composi-
tion of the ash of the coal with that of the fireclay but this has not
proved to be an entirely satisfactory means of settling the question.
The clay in any case is mineral matter and there is always more or
less of this in coal, carried in by wind and water from surrounding
lands, and while it may be similar to that in the plants it is independ-
ent of the composition of the ash of the wood. It is probable that
some clays are at least partly chemical sediments.

There is much need of further information regarding these inter-
esting and valuable rocks. It seems very probable that the clays
were deposited as part of a normal series of sediments and that

1 Arber, E. A. N., The natural history of coal, p. 91, 1912.

CLIMATIC CONDITIONS 155

the growth of plants helped to destroy the stratification and to
extract certain of the soluble salts; but the plants were not abso-
lutely necessary for the formation of the clay nor was that kind of
clay necessary for the growth of the vegetation as demonstrated by
modern swamps and peat-bogs.

Climatic Conditions

Concerning the climate of the coal-forming periods there is some
difference of opinion among paleobotanists. They are our chief
judges in this discussion because we are dependent mainly upon the
plants of those periods for indications of climatic conditions. There
is one feature, however, concerning which there is unanimity among
all the best authorities, and that is that the climate was uniform over
great areas of the earth's surface. This is demonstrated by the
fact that the same genera and some of the same species of plants of
Carboniferous age are found distributed over both hemispheres from
the tropical to the polar regions. A similar condition prevailed again
in Jurassic and Cretaceous times. As to the cause of this uniformity
little is definitely known. It has been suggested by some geologists
and botanists that this condition was due to a greater amount of
carbon dioxide in the air than there is in normal times and Cham-
berlin 1 has described in detail how its presence might be brought
about. Other factors which might aid in producing this uniform
condition are the relation between sun and earth in position and dis-
tance and changes in the distribution of land masses in the sea, per-
mitting warm ocean currents to reach the polar regions and melt
the ice.

There is also little doubt concerning the humidity of the atmosphere
during the coal- forming periods. This is necessary for the growth
of such enormous quantities of plants in order that they may give
rise to coal. Humidity and uniformity in climate are rather closely
related. Further, if we accept the in situ theory for the origin of
coal, sufficient water to cover the fallen vegetation is essential for
its preservation and the warmer the climate the more the water re-
quired.

As to whether the climate in the Carboniferous and other great
periods of peat formation was hot is a debated question among paleo-

1 Chamberlin and Salisbury. Geology, Vol. Ill, p. 432, 1906.

156 THE ORIGIN OF COAL

botanists. Arber 1 claims that there is nothing in the Carboniferous
flora so far as known to prove that it was tropical in character, as
luxuriant forests may be found today in temperate regions and the
large cells of the plants do not necessarily indicate tropical conditions.
White 2 believes that the climate was humid, uniform and mild, being
generally either tropical or sub-tropical. Some evidences of these
conditions are the similarity in character between many of the plants
now found in tropical swamps and those found in coal formations.
The absence of growth rings in the trees indicates uniformity in seasons
and the wide distribution of almost identical floras indicates uniform-
ity in climate over wide areas of the globe. The large leaves and
fronds, and the large cells with thin walls indicate rapid growth. The
stomata are protected in grooves on the under sides of leaves of many
plants and subaerial roots are found on many species. The seeds
show provision for flotation and delayed fertilization. The presence
of tree ferns, palms, and cinnamon trees in the Tertiary coal deposits
suggests tropical, or at least sub-tropical conditions.

There is one rather peculiar association of plants known as the
Gangamopteris, or Glossopteris flora, which in Permian time spread
widely over the Southern Hemisphere. It is different from the
other coal-formation floras because of its close association with glacia-
tion. It is found in Australia, India, South Africa, South America,
and to some extent in Russia, where Glossopteris and Gangamop-
teris are abundant in the vicinity of Moscow.

In Australia the Permo-Carboniferous, or possibly more strictly,
the Permian system, forms a very thick group of rocks containing
extensive coal seams, which are of fresh- water origin and which in
most cases show evidences of autochthonous origin by the presence of
roots in the underlying clays. This group also contains thick beds
of tillite showing that glacial conditions were prevalent at that time
and that there were at least two great interglacial periods. A con-
densed description of these rocks taken from David's work is as
follows: 3

1 Arber, E. A. N., The natural history of coal, Cambridge University Press, p. 70, 1912.

2 White, David, The origin of coal, U. S. Bur. of Mines, Bull. 38, p. 68, 1913.

3 David, T. W. E., British Ass. Adv. Sci. Handbook for Australia, p. 257, 1914. See
also Siissmilch, C. A. An introduction to the Geology of New South Wales, p. 93, Sydney,
1914.

TRANSFORMATION OF VEGETAL MATTER INTO COAL 157

Thickness
Ft.

1. Acid granites of New England

2. Upper or Newcastle coal measures; with 35 to 40 feet of workable

coal. Glossopteris predominates over Gangamopteris. Dadoxy-

lon abundant 1500

3. Dempsey Series; Barren fresh- water shale 2200

4. Middle coal measures; with 20 feet of workable coal 500-1800

5. Upper Marine Series; with marine fossils and glacial erratics ... 6400

6. Lower or Greta coal measures; with about 20 feet of workable coal.

Gangamopteris predominates over Glossopteris 100-300

7. Lower Marine Series; with marine fossils. Basalts and tuffs.

Glacial beds 300 feet thick at base 4800

At Bacchus Marsh, Victoria, there are four beds of tillite in a for-
mation 2000 feet thick. These glacial beds have been correlated with
the Dwyka conglomerates of South Africa. In one place Ganga-
mopteris occurs with a local coal seam in the upper part of the Lower
Marine series, in fresh-water deposits.

So far as known the Glossopteris flora does not occur in the typically
Carboniferous strata which reach 20,000 feet in thickness in Australia,
nor is Lepidodendron found in the Permo-Carboniferous although
prevalent in the Carboniferous and upper Devonian. No doubt the
great change in climate was too severe a test for Lepidodendron and
related plants and they disappeared during the glacial conditions.

Although there were two glacial periods associated with the coal
seams of the Permian, there is no evidence that there was a sudden
change in climate and that the Glossopteris and Gangamopteris
flora lived under frigid conditions. These glacial epochs were separ-
ated by long periods of time and when it is considered that during
the apparently much shorter interglacial periods of the Pleistocene
in America such trees as the pawpaw (Asiminia triloba) and the osage
orange (Madura arantiaca), now found only considerably farther
south, grew at Toronto, Canada, 1 it seems probable that Australia
may still have had a reasonably mild climate during the formation
of the important coal seams of Permian age.

The Transformation of Vegetal Matter into Coal

It is generally recognized that when vegetation changes to coal it
passes through two stages, the first being known as the biochemical
and the second as the dynamochemical stage. As these terms indicate,

1 Coleman, A. P., Interglacial fossils from the Don Valley, Toronto. Amer. Geol.
Vol. XII, p. 86, 1894.

158

THE ORIGIN OF COAL

the first process is due chiefly to the action of bacteria and other low
forms of life and the second to geological forces capable of produc-
ing chemical and physical changes in the vegetal matter.

The biochemical process, or the first stage in coal formation.
When plants in a bog or swamp cease to grow, and fall, they are
subject to attacks from bacteria and other low organisms. The
most extensive investigations on this subject have been carried on
by Renault, 1 the French scientist, who spent most of his later years

I J

FIG. 31. Bacteria in the cuticle of bothrodendron from the "paper coal" (x 800) (a)
Bacillus exiguees (b) Isolated micrococcus (c) Micrococcus in process of division (d) Micro-
coccus in colonies (e) Spores of bacilli. (After Renault.)

in studying and identifying new species of bacteria in the coals. It
is unfortunate that when Renault did such excellent work on this
subject he should have permitted himself to go to extremes in his
ideas of the prevalence and importance of these fossil organisms in
the coal. Having had the privilege of examining his original slides
the writer is convinced that many objects taken for bacteria were
specks of mineral matter and in some cases, at least, crystallized or-
ganic matter. Similar conclusions have been reached by others
who have investigated this subject. Renault has shown, however,

1 Renault, B., Loc. cit. Also du role de quelques bacteriace'es fossiles au point de
vue geologique. Congres Geologique International, pp. 646-663, 1900.

THE BIOCHEMICAL PROCESS

159

that a great many bacteria have been sufficiently well preserved to be
recognized and to show that they undoubtedly did a great deal to
macerate the vegetal matter (Figs. 31 and 32). There have been
recognized representatives of the living forms such as Micrococcus
and Streptococcus in ad- r miTTim

dition to many others.
These forms were most
active in the upper
layers of the peat be-
cause the lower portions
of the bog were so
charged with organic
solutions of ulmic, crenic
and other acids resulting
from chemical action
that the bacteria could
scarcely exist. Although
no quantitative study
has been made of this
subject it is believed
that their action extends
to comparatively shallow
depths.

In addition to the
bacteria there are many

)

FIG. 32. Chains of bacilli in coal of arthropitus
(x 1200) (a) Chainlet of bacilli mostly diplospores
(b) Group of arthrospores (c) Chain beginning to
ramify. (After Renault.)

larger plants, especially
the fungi, which help to
produce chemical
changes and aid in the
maceration of the plant debris. Among these, mushrooms and related
plants probably play an important role. The action in all cases
seems to result in a change from the production of oxygenated hy-
drocarbon compounds of the living plant to a breaking up of these
into such simple compounds as the oxides of carbon. When the
latter compounds are formed the hydrogen must then be free to form
simple compounds with carbon and with oxygen such as methane, and
water.
In addition to the bacterial action being halted by acid compounds

160 THE ORIGIN OF COAL

resulting from their own action, it may be stopped by burial of the
peat under layers of sediment or by mineral matter, deposited from
solution, surrounding the plant debris. The latter action is well
illustrated by the concretions commonly called "coal balls" found
in many seams, or in the rocks overlying them. These bodies fre-
quently contain perfectly preserved plant remains showing that the
mineral matter must have sealed them up almost immediately after
they fell.

The second stage in codification: It seems to be generally admitted
that biochemical processes are responsible for the early stages in the
alteration of the plant debris as it changes to coal of any kind or even
to old compact peat. There is a much greater divergence of opinion,
however, regarding the processes which continue the alteration until
different varieties of coal result. Since the greater number of ob-
servers consider that the second stage is produced almost entirely
by dynamochemical action this stage in the process is very frequently
discussed as if the dynamochemical were the only factor to be taken
into consideration, but several other hypotheses have been advanced
in opposition to the dynamochemical theory.

The various suggestions to account for the development of different
varieties of coal from vegetal matter may be summed up as follows:
(i) Differences in kinds of vegetation and differences in climates in
different regions. (2) The length of time during which the vegetation
has been exposed before burial by sediments. (3) Length of time;
since burial of the vegetation. (4) The depth of burial of the vege-
tation. (5) Action of heat from compression or from intrusions of
igneous rocks. (6) Possibility of escape of volatile constituents after
burial beneath sediments because of fractures or pores in the over-
lying rocks, and jointage in the coal seams. (7) The pressure re-
sulting from compression of the seam during dynamic changes in the
enclosing rocks.

1. Different kinds of vegetation and different climates. An
examination of the different varieties of coal, omitting special types
like cannel, will show that they differ very little in their physical
composition. They all, whether lignite or anthracite, contain light
and dark bands, fragments of resin, spores, fragments of bark and
other plant debris. This seems to indicate that they may have been
derived from the same type of vegetation. Anthracite has not been

DIFFERENT KINDS OF VEGETATION AND CLIMATES

161

shown to contain a greater proportion of spores, resin or other portions
of the plant than bituminous coal. It is well demonstrated that in
an anthracite region a seam will be anthracite throughout and not
in patches only like the cannel in bituminous coal seams. The fol-
lowing analyses will show that various types of trees are so nearly
alike in chemical composition that it would be impossible to put
them through the same geological processes and expect to get different
kinds of coal from them.

Wood

Ash

Calorific
power

Oak

0.37

50.16

6.03

4,620

Ash

0.57

4Q.i8

6.27

4,711

Hornbeam

o. 50

48.99

6. 20

4,728

Beech

0.57

4Q.o6

6. ii

0.09

4,770

Birch

0.29

48.88

6.06

O.IO

4,771

Fir

0.28

50.36

5-29

0.05

5,035

Pine

0.37

50.31

6.20

0.04

5,085

Cellulose

44-4

6.2

*' o

4,140

Table by Gottlieb.
&Co.

From Cellulose, by Cross and Be van. Longmans, Green

Plant

Ash

i. Lycopodium dendroideum
3. Lycopodium complanatum . . . .
5 Equisetum hyemale

47.11
45-78

41 Q4

6-39
6.25
5-8q

41.85
40.66
?Q .23

.40

.84

. 12

3-25
5-47
II .82

7. Asidium marginale

44 77

c no

41 .97

.08

c.iq

9. Cyathea camculata

4? . ?o

6. II

30.82

. 12

7.56

n. Cyathea caniculata

48.72

4.89

38.48

.42

6.4Q

Analyses by G. W. Hawes. 1 Nos. 1,3,5 and 7 are average samples of the part
of the plant above ground, including spores. Nos. 9 and n are tree ferns from
Tahiti. No. 9 is an analysis of a section of the stem and No. n of the cortical
part.

Analyses of coal derived from different genera of Carboniferous
trees were made by Carnot and it can be seen that the differences in
composition in coal from Lepidodendron, Cordaites or Ptychopteris
are negligible, the maximum difference in carbon being only 2.66
per cent and in hydrogen 0.03 per cent.

The plant fossils were identified by Renault and carefully selected

1 Hawes, G. W., On the chemical composition of the wood of acrogens. Amer. Jour.
Sci. ( 3 rd Series) Vol. 7, p. 585, 1874.

162 THE ORIGIN OF COAL

to obtain any differences in the coal which might be due to differences
in the original vegetation.

It can be concluded that different types of plants cannot produce
any material difference in the nature of the coal formed and that they
have no particular bearing on the origin of anthracite. It is recog-
nized, however, that different portions of the plant such as spores
or resin, the latter of which may contain over 80 per cent of carbon,
may form different types of coal if separated from the other plant
debris and segregated in sufficiently large masses. There is, how-
ever, no evidence whatever that such has been the case in the for-
mation of anthracite.

As for differences in climate producing any marked variation in
the coal of different regions, there is no ground for accepting such a
theory as all vegetation must be covered with water to preserve it.
There is no great difference in the peat formed from trees in the
tropical and temperate zones.

2. Exposure before burial. It is a recognized fact that if wood be
exposed to the air certain portions will decompose before other por-
tions and there will be a relative increase in carbon and a decrease in
hydrogen and oxygen. The wood usually decomposes first and leaves
the more resistant bark and related tissues. To illustrate the change
which occurs, the following analyses are quoted from Fayol's work. 1

Carbon in bark of oak, 29.65 per cent; in sound wood 21.95 to 22.82
per cent; in the same tree, slightly decomposed, 24.75; mor e decom-
posed, 27.60; and rotten, 31.00 per cent. Analyses by Pollard of
dark and bright coal from a seam in Wales show carbon in bright
band 63.96, and in dull powder 77.17 per cent, and since the dull
layers of mineral charcoal are generally thought to have originated
through extensive rotting of the vegetation before burial these figures
show that there undoubtedly may be considerable difference produced
in the composition of the resulting material by more prolonged ex-
posure before burial. When one attempts to employ this as a means
of explaining the origin of the great deposits of anthracite it is useless,
however, because these dull layers are present in bituminous coal also,
and they are distributed throughout the anthracite seams in such a
way as to indicate that they have no bearing on the anthracitic char-
acter of the seam taken as a whole.

1 Fayol, H. Loc. cit, p. 171.

LENGTH OF TIME SINCE BURIAL 163

It has been suggested that the anthracite field of Pennsylvania
owes its origin to longer exposure of vegetation laid down in the east-
ern part of the state than that deposited in the west because of a
gradual migration westward of the coastal plain on which the plants
grew. This assumption scarcely seems justified because it is probable
that the swamp or swamps which gave rise to the Pennsylvanian coal
deposits were spread pretty uniformly over the anthracite and bitumi-
nous areas at the same time. Further, the anthracite region being
closer to Appalachia, the main source of supply for clastic sediments,
it is probable that the vegetation was buried early in the history of
these deposits In their studies of the South Wales anthracite de-
posits Strahan and Pollard state that no definite relation exists be-
tween the position of the anthracitized beds and the old shore-
line.

3. Length of time since burial. A general impression exists among
many people interested in coal that the ag of the coal has an impor-
tant bearing on its quality. To a certain degree this assumption is
correct, because, other things being equal, the older coals will be
higher in the peat-to-anthracite scale than the younger ones, not
simply because the vegetation was formed in any particular geologic
period, but because the metamorphosing processes have had longer
to work and the older rocks have as a rule been more deeply buried
and subjected to greater pressures than the younger rocks. There
are many examples on record where seams of Carboniferous age are
still in the form of brown coal or lignite. Such a case is found in
Western Australia where a small area of Permo- Carboniferous meas-
ures was faulted up and preserved from intense pressure. The coal
is still brown coal, although practically all other Penno-Carbonifer-
ous coal in Australia is bituminous or anthracite In Russia brown
coal occurs in the Mississippian, or Lower Carboniferous, while in the
western states and Canada and in many other countries the Cretaceous
and Tertiary coals, which are more typically lignite, have been altered
to high-grade bituminous coal or even anthracite in local areas.

In connection with this discussion on the length of time since
burial of the vegetal matter, the question of the length of time a bed
of vegetation must be buried before it is changed to coal may be con-
sidered. We have very little definite information on this subject
but there is a clue in the occurrence of coal pebbles in the rocks asso-

164 THE ORIGIN OF COAL

dated with coal beds. Renault and Fayol 1 have discussed the coal
grains and pebbles in the Coal Measures in the Commentry basin in
France. That these are water-borne fragments of coal and not frag-
ments of wood buried in the sandstones and conglomerates and later
transformed into coal is indicated by the fact that they have not
shrunk nor have they been deformed in shape as they would have
been had they consisted of wood and been turned into coal after their
burial. They must represent fragments of a deposit lower in the
Carboniferous which had already changed to coal and been broken up
by erosion.

In England there are also pebbles of coal high up in the Coal Meas-
ures which Strahan considers as distinct fragments of coal derived
from an eroded coal seam lying a few feet below the Pennant grit
which carries the pebbles. There is no older coal formation in the
region which could urnish these pebbles. These examples indicate
that coal must form quite, rapidly from the vegetation.

As modern examples of wood changing to coal in very short
spaces of time, a case occurring in the vicinity of Scranton, Penn-
sylvania, is cited by Moffat. 2

A mine prop left standing and surrounded by mine refuse was sub-
jected for about 30 years to high pressure from the roof and to high
temperature from a mine fire, although the fire did not actually reach
the prop. Different parts of the prop suffered varying degrees of
alteration The lower portion was well preserved wood; about half-
way up it was a little charred externally and above this it was turned
into friable, soft charcoal. The upper part and especially the cap
wedge, which had suffered from great compression and had been
crushed down, was greatly altered and had a conchoidal fracture like
anthracite coal, a jet black color, a bright glossy luster, and a specific
gravity of 1.38. It burned with a feeble flame. Analyses showed
that it contained: Moisture at 100, 5.65; Volatile Matter, 43.05;
Fixed Carbon, 51.00; and Ash, 0.30 per cent. It would appear that
although heat aided this change the pressure was necessary to produce
the coaly character, as distinguished from charcoal. The wood in
this prop and wedge retained its structure very well.

1 Op. cit.

2 Moffat, E. S., Note on the formation of coal from mine timber, Trans. Amer. Inst.
Min. Eng., Vol. 15, p. 819, 1886.

1 1

^ I

. .9

1 66 THE ORIGIN OF COAL

Daubree 1 and Fremy have produced materials resembling coal
from various woody constituents at temperatures from 200 to 300 C.
It was found that woody fibers, as vasculose and cellulose, became
black and brittle but retained their organization and did not fuse;
while such substances as starch, sugar, gums, and chlorophyll became,
when subjected to heat and pressure, black, brilliant, and insoluble
like coal. The latter substances will also leave a coke. This may
account for some of the differences between lignite and black lignite,
or subbituminous coal, the one originally having more woody material
than the other.

From all available evidence it would appear that coal may form in
a very short time, geologically speaking, if conditions be favorable.
The chief factors producing the change are heat and pressure.

4. Depth of burial. The depth of burial is so closely related to
the compression resulting from crustal movements that these two
factors may be considered together. It should be pointed out, how-
ever, that there are few, if any, cases where it can be shown that the
depth of burial alone was sufficient to produce anthracite, although
it is such a generally recognized principle that the fixed carbon in-
creases and the volatile matter decreases with depth in a series of seams
that this principle is commonly known as the Law of Hill, after the
man who expounded it. It has been stated by some writers that
there is a definite relation between the depth of the seams and the
anthracitization of the coal in the basin of Commentry in France,
but this statement will not hold in all cases. Strahan 2 has pointed
out that in the South Wales field the cover of not only the Palaeozoic
rocks but also of the later rocks over the bituminous field is much
thicker than that over the anthracite field. He states further, how-
ever, that in general the conclusion of De la Becke and Joseph that
the lower seams in the anthracite field were more anthracitic than the
upper was correct but this will not hold for all seams throughout the
field. The chart of iso-anthracitic lines (Figs. 33 and 34) brings out
clearly the relation between the various seams in this field. White 3

1 Daubree, fitudes et experiences synthetiques sur le metamorphisme et sur le for-
mation des roches crystallines, p. 72, 1860.

2 Strahan, A., and Pollard, W., The coals of South Wales, with special reference to
the origin and distribution of anthracite. Memoirs Geol. Survey, England and Wales,
2nd Ed., pp. 73 and 74, 1915.

White, D., Op. cit., p. 126.

DEPTH OF BURIAL

167

has pointed out that of 20 cases where two or more of these seams were
vertically 100 feet or more apart the analyses show only one case
where there was a downward increase of volatile matter. Two cases
show no difference and the others show an average loss per 100 feet
of descent of 0.6 per cent volatile matter. In American seams, out of
thirty-four cases twenty-nine show an average decrease of 0.38 per
cent volatile matter per 100 feet descent. Quoting from Van der
Gracht, White states that at Helenaveen the decrease in the gas coal
is about 0.53 per cent; at Helden in the coking coal about 0.8 per
cent; at Baarlo about 0.62 per cent; and in Westphalia, 0.51 per

FIG. 34. Relation between depth and the carbon-hydrogen ratios in three seams
in the South Wales coal field. (After Strahan and Pollard.)

cent for gas coal and 0.71 per cent for coking coal per 100 feet. In
Pennsylvania the depth of the anthracite seams cannot be taken as
a criterion for the alteration which the coal has undergone but in
some of the semianthracite areas of China there seems to be a more
marked connection between the depth at which the seams lie and the
degree of anthracitization There must, however, also be taken into
consideration the factor of thrust, a subject which will be discussed
later.

1 68 THE ORIGIN OF COAL

5. Effects of heat. That heat from igneous rocks aided by the pres-
sure which must be an accompaniment of intrusions can produce an-
thracite from bituminous coal has been proven beyond a doubt. In
Colorado, Alaska, New Mexico, and in numerous countries, natural
coke, anthracite, and other types of coal have been produced from
bituminous coal by igneous rocks. The effects of igneous intrusions
are, however, quite local and they have not been responsible for the
anthracite in the great fields of South Wales and Pennsylvania. In
the Cerrillos Coal Field of New Mexico, considerable anthracite,
mostly of secondary grade, has been produced as a result of the in-
trusion of a great sill about 400 feet thick along the surface of a coal
seam, but the effects extend only a comparatively short distance from
the sill. As a rule there is some relation between the width of a dike
or thickness of a sill and the width of the zone of coal affected, but
this varies greatly. Usually the coal is not affected much beyond
the width of the dike. It should be remembered in this connection
that an igneous rock intruding coal will affect it much as it does other
rocks which it intrudes. In some cases a dike or sill will scarcely
metamorphose the adjacent rocks due to the fact it was almost cooled
when it reached them or it may have had little hot gas or water to
give off to attack the adjacent rocks. Some intruding rocks were
hot and, carrying much hot gas and water, were capable of profoundly
altering the surrounding rocks. As a rule acid rocks, such as granites
and rhyolites, are capable of existing in the liquid condition at lower
temperatures than the basic rocks like gabbros and basalts or traps,
but they usually carry more liquids and gases and are, therefore,
capable of producing more metamorphism at the temperature of
intrusion than are rocks without these agents.

In 1869 Bevan 1 attempted to explain the origin of the South Wales
anthracite as due to trap rocks but it has been shown that these
igneous rocks were earlier than the coal seams. The formation of
Pennsylvania anthracite has also been assigned to the heat of igneous
intrusions but there are no intrusions worth mentioning in this coal
field and those intrusions which do occur are Triassic in age and much
later than the coal. Intrusions of the same age and character occur
also in the bituminous field of Pennsylvania without appreciably
affecting the bituminous character of the coal. It must be admitted
1 Bevan, J. P., The geologist, Vol. II, p. 75, 1869.

ESCAPE OF VOLATILE CONSTITUENTS 169

that the influence of igneous rocks is very limited although neverthe-
less real.

6. Escape of volatile constituents through fractures and pores.
In order to explain the lack of anthracitization of coal in areas of
intense folding and even where the temperature has been rather high,
Campbell 1 has suggested that fractures such as joints or cleavage
in the coal and adjacent rocks have been responsible for this process.
He assumed that the transformation of one type of coal to another,
higher in fixed carbon, was primarily due to heat although not neces-
sarily to a high temperature and that time was a very important
factor in connection with the results derived from heating. Pressure
may be important in producing heat by compression and in aiding
the driving off of the volatile constituents but unless there be a means
of escape for these there cannot be much change in the coal either
from compression or heating. The process may operate if the en-
closing rocks be porous, and overlying coarse sandstones would be
much more favorable than shales for the escape of volatile constituents.
In support of this principle he cites the graphitic coal of Rhode Island
as an example of coal carried to the extreme condition of carbon-
ization because of extensive fracturing permitting escape of volatile
constituents. The anthracite of Pennsylvania is more fractured than
the bituminous coal, and the lignites of North Dakota and Texas are
overlain by impervious clays. This hypothesis is said to apply
equally well to all the coal fields studied in the United States.

Since there is no doubt that the coal changes to a higher carbon
type by loss of gases Campbell's principle is perfectly logical but
there are some limitations which should be kept in mind, and this
may explain why some highly fractured coal has not been altered to
a high carbon type. The extensive fracturing of a rock is evidence of
yielding to stress, and the pressure which would have been exerted on
the coal, if the rock had not been broken, is relieved by fracturing,
with the result that both heat and pressure are lost. There is ap-
parently a proper balance between the length of time the coal suffers
pressure and the fracturing, because if the fracturing occurs too early
in the process insufficient pressure may be exerted.

There are many coal seams which contain an abundance of gas

1 Campbell, M. R., Hypothesis to account for the transformation of vegetable matter
into the different grades of coal. Econ. Geology, Vol. I, p. 26, 1905.

170 THE ORIGIN OF COAL

which escapes by blowers or by oozing out during the mining oper-
ations. This coal is not necessarily lower in fixed carbon than other
coal which does not give off so much gas during mining, because it
has absorbed the gas in its pores. If the pressure be sufficiently great,
the gas will be compressed and will remain in the coal, but in all
cases where it cannot escape an equilibrium will be established be-
tween the volatile constituents attempting to escape and the com-
pressed gas already given off. It is evident, however, that other
conditions being equal less pressure will be required to raise the coal
to a higher type if the gas can escape.

7. Effect of pressure. Although there may appear to be many
exceptions to the rule it must be generally recognized that anthracite
and other high-carbon coals are characteristically found in regions of
crustal disturbance the world over. Anyone reading the descriptions
of coal fields will find that if any country contains anthracite it is
invariably found in its mountains or disturbed areas, and this con-
dition goes a long way towards establishing the thrust-pressure hy-
pothesis for the origin of anthracite. This hypothesis has in recent
years been worked out in great detail by White 1 for the United States,
and he has shown that this is the most logical explanation for the
devolatilization of coal in its second stage of development.

There are certain geological factors entering into a consider-
ation of such a hypothesis which have not always been given due
consideration. In almost any coal field there will be found a series
of sediments made up of heavy, strong beds, such as sandstones or
conglomerates, known as the competent beds; and others, such as
coal and shale, which comprise the incompetent beds. When pressure
is applied to these strata the incompetent beds yield and adapt them-
selves to the movements of the competent beds which are sufficiently
strong to resist buckling. If the beds always lay perfectly horizontal,
or the thrusts were always applied parallel to the bed and equally to
all the competent beds there would be no important result. In such
a heterogeneous column of strata, however, there are oblique thrusts
and therefore movements of one rock over another in various direc-
tions, with the result that great pressures are exerted on the coal and
the shale but the adjacent competent rocks have suffered very little

1 White, D., Op. cit., p. 105; and, Some problems of the formation of coal. Econ.
Geol., Vol. 3, p. 292, 1908.

EFFECT OF PRESSURE 171

deformation. This condition is well illustrated in Figure 63, where
one formation is highly contorted but the rocks above and below show
no effects of the pressure. Coal acts as a plastic mass in the early
stages of its development from vegetal matter as illustrated by Figure
74, and it is then capable of accommodating itself to almost any
shaped space without showing any trace of the movement. These
structural principles may offer an explanation of the flat-lying an-
thracite seams in the Wyoming basin in Pennsylvania and in the coal
fields of China. A highly fractured stratum is not always evidence
of excessive pressure having been applied in that area but it is evidence
that the pressure was relieved. It may not have done more than a
small fraction of the work in devolatilizing the coal which it would
have done had it been applied to a competent bed capable of with-
standing that pressure and of transmitting it to the coal seam. A
small amount of heat thus generated and held there for a long period
of time, would devolatilize the coal.

If this principle be applied to the well-known anthracite fields of
Pennsylvania and South Wales it is believed that it will explain most
of the features. The Pennsylvania field lies in a highly disturbed
area along the main limb of the anticlinorium forming the Appal-
achian Mountains to the southeast and the synclinorium forming the
Appalachian Valley to the west of this field. There is, when con-
sidered on its broader lines, a marked difference between the com-
plicated structure of this region and that of the comparatively simple
structure of the bituminous field farther west. It is probable that
this area suffered an unusual amount of compression where the mount-
ains were developed and the fact that there are small, comparatively
undisturbed areas within this region is no evidence that they did
not suffer from intense thrust pressure. The thickness of the whole
series of strata concerned in the great crustal movements must have
also affected the pressure exerted on the coal seams although the seams
lie near the top of the series. The strata were very thick, probably
upwards of 25,000 feet in that region. The accompanying map of
Pennsylvania showing the fuel ratios of the coal in various parts of
the state illustrates the relation between the anthracite and bitu-
minous areas and shows the gradation from one to the other (Fig.
35)-

Turning to the South Wales anthracite field, so well described by

172

THE ORIGIN OF COAL

EFFECT OF PRESSURE

173

o.^Z

;u_z

Strahan and Pollard, 1 a gradual change from an T
thracite to bituminous coal is found, but with
the peculiar condition that there is a marked
increase in the ash in the latter, a condition
which would not be expected if part of the bi-
tuminous coal gave rise to anthracite by de-
volatilization. The ash content as indicated by
all analyses available varies from about i per
cent at the anthracite end to 6 per cent at the
bituminous end. (Fig. 36.) Various explana-
tions have been offered to explain this, such as
differences in the original vegetation and differ-
ences in the extent of decomposition before
burial of the vegetation. These are not satis-
factory because there is no evidence that the
vegetation in these areas was different and if
it were it would require that practically all the
coal in the bituminous area be derived from
Equisetum or some such plant to give rise to so
much ash. If the same plants underwent diff-
erent degrees of decomposition, this would tend
toward higher carbonization and therefore an-
thracitization but it certainly would not reduce
the relative ash content in the anthracite. It
would appear that the only explanation is found
in the addition of more mineral matter to the
vegetation while it was accumulating, or later
by action of ground water percolating through
the rocks.

It has been clearly shown that the anthra-
citization was not the result of igneous intru-
sions, nor does there seem in all parts of the
field to be any relation between the lines of
iso-anthracitization, and the original outline of
the basin in which the coal was deposited, or the
present outline of the basin. Strahan and Poll-
ard have shown that there is with few excep-

1 Strahan, A., and Pollard, W., Op. cit., p. 80.

174 THE ORIGIN OF COAL

tions a regular increase in anthracitization with depth and also in going
westward from the eastern border of the basin, but they conclude that
there is for them no satisfactory explanation for the origin of the an-
thracite. Differences in original vegetation are not satisfactory; nor is
the metamorphism by pressure hypothesis substantiated as the iso-an-
thracitic lines do not correspond with the lines of disturbance, and
the faulting which has so profoundly affected the region was later
than the formation of the anthracite and has had little influence on it.
Although the carbon-hydrogen ratio increases with depth there seems
to be little or no difference between the coal in the anticlines and that
in the synclines.

White considers that the isovols, or lines of equal volatile matter,
in this field follow closely lines normal to the thrusts and that if the
area were worked out on this basis the thrust-pressure hypothesis
would explain the anthracitization. In the writer's opinion this is
the only explanation, and the composite chart in Figure 33 indicates
that the iso-anthracitic lines follow the outlines of the basin except
for variations which would be the logical result of thrusting. An
example of this may be seen on the chart in the Rhonda No. 2
vein.

The best hypothesis so far offered for the origin of anthracite and
the one which it is believed will explain its origin in all the fields so
far studied, if logically applied, is the thrust-pressure hypothesis.

The Origin of Cannel and Boghead

As early as 1833 Hutton 1 examined cannel coal under the micro-
scope and found small " cells " which he said were of a resinous
nature and contained a wine-yellow " liquid." This seems to have
been the first time that the spores of cannel coal had been noticed.
Balfour, Huxley, Dawson, Bertrand, Renault, and Jeffrey have
since that time, in turn, studied these spores in detail and added much
to our knowledge concerning them. There is now no doubt but that
cannel consists almost entirely of spores and spore exines with some
of the other more resistant portions of the vegetal matter. These
bodies collect in open water and form layers usually of lens-shape,
in the other types of coal.

1 Hutton, W. Observations on coal. London and Edinburgh Phil. Mag. and Jour,
of Sci., Vol. II, p. 302, 1833.

THE ORIGIN OF CANNEL AND BOGHEAD

175

Cannel bears certain resemblances to the bogheads, including the
varieties Torbanite, oil shales, kerosene shales, and bituminous schists.
There seems to be little
doubt that the organic
matter of the latter
rocks is a step nearer
petroleum and natural
gas than that of the or-
dinary coals and in this
way petroleum is related
to all coals through these
types high in volatile
constituents, especially
the lighter hydrocar-
bons, and lower in the
carbohydrates. The best
known deposits of these
rocks are the Torbanite
of Scotland, the bitu-
minous schists of Autun,
France, and the kerosene
shale of New South
Wales, Australia.

Largely as a result of
the work of C. E. Bert-
rand and B. Renault 1 it
became generally accep-
ted that these bogheads
were formed from gela-
tinous algae. The rocks
were studied micro-
scopically and certain

FIG. 37. (a) Horizontal section through the bog-
head of Autun showing Pila bibractensis (x 17), (6)
Vertical section of same (x 38). (After C. E. Bert-
rand.)

minute bodies were recognized as the thalli of algae (Fig. 37).

1 Renault, B., and Bertrand, C. E., Note sur la formation schisteuse et le boghead
d' Autun. Bull. Soc. 1'industrie minerale, Tome 7, 3me Ser., p. 499, 1893. Also, Pila
bibractensis et le boghead d'Autun. Soc. d'Histoire Naturelle d'Autun, Bull. 5, p. 159,
1892. Also, Reinchia Australis et Premieres Remarques sur le Kerosene Shale de la
Nouvelle-Galles du Sud. Soc. d'Histoire Naturelle d'Autun, Bull. 6, p. 321, 1893.

176 THE ORIGIN OF COAL

Bertrand 1 describes the algae as occurring as a hollow, compressed
sack lying in a brown jelly, which is known as the fundamental jelly
and which is said to carry many bacterial bodies. Between the
thalli there are spores and grains of pollen forming thin laminae of
orange or reddish-brown color. It is stated that the algae carry
solid material to the extent of 0.015 to 0.030 of their volume.

Various names were applied to the supposed algae from different
regions. Those from the boghead of Autun were known as Pila
bibractensis and those from the kerosene shale of New South Wales
as Reinschia australis. As Thiessen 2 has pointed out, however, there
are many unsatisfactory features in Bertrand's explanation of the
source of the bituminous matter which formed the fundamental jelly.
Jeffrey 3 has attacked the works of Renault and Bertrand and has
shown by means of modern section-making methods that these sup-
posed algae are not thalli of algae but spores of vascular cryptogams.
The openings in the supposed thalli are the tri-radiate lines on the
spores. He explains the difference between cannel coals and boghead
as due to the fact that the latter are composed of larger spores than
the cannels, i.e., they consist chiefly of macrospores. The fact that
oil shales derive their oils and gases from spores has been verified by
other investigators.

Jeffrey's conclusions have been generally accepted but one writer
claims that he has obtained very strong evidence in support of the
algal theory in some recent deposits in Russian lakes. M. D. Zalessky 4
states that he was inclined to agree with Jeffrey until he saw well
preserved, silicified specimens of Pila from Autun and he has recently
examined algal deposits which are now forming. In the brackish,
shallow lake, Ala-Kool which lies at the southern extremity of the
fresh- water lake known as Balkhash and which is overgrown with
aquatic plants there lives the oleaginous alga, Botryococcus braunii

1 Bertrand, C. E., Charbons gelosique et charbons humique. Compte Rendu VIII,
Congres Geologique International, p. 458, 1900.

2 White, D., and Thiessen, R., The origin of coal. U. S. Bureau of Mines, Bull. 38,
pp. 198-199, 1913-

3 Jeffrey, E. C., The nature of some supposed algal coals. Proc. Amer. Acad. Arts
and Sciences, Vol. XL VI, p. 273, 1910.

4 Zalessky, M. D., On the nature of pila, the yellow bodies of boghead and on sapropel
of the Ala-Kool Gulf of Lake Balkhash; Extrait du tome XXXIII des Bulletins du
Comite" Geologique, St. Petersburgh, No. 248, 1914.

EFFECT OF PRESSURE 177

in such superabundance that it would appear that sapropel might
form from it on the lake bottom as in the case of the bogheads in
Permian and Carboniferous time. The plankton algae come to the
surface and they have been analysed by S. L. Ivanov, who obtained
the following: Oil, 3.5 per cent; number of free fatty acids, 12;
ether number 16; saponification number 28; iodine number 55.4.
The sapropelic crust formed along the edge of the lake was also ana-
lyzed and with ether yielded 25 per cent of its substance. The ether
was then evaporated and a hard, wax-like mass remained. This
mass gave acid number 93.5 per cent; ether number 46.7; saponi-
fication number 140.2; iodine number 31.5; nitrogen, 0.4003 per cent.
Oleinic acid was believed to be present.

A hydrogen sulphide fermentation takes place in the mass and when
it is exposed to the air it changes from a green, movable body into a
yellow-brown solid, elastic and reminding one of a mass of rubber,
which can be cut with a knife. Thin sections show some preserved
cellular structure of algae, the cavities of the swollen cells being
represented by roundish pores. Zalessky claims that these are very
similar to the structures seen in the silicified bogheads of Autun
prepared as suggested by Jeffrey and he considers that Pila and
Botryococcus are strikingly alike. The mud of Ala-Kool consists
almost exclusively of algae of this type with a few other green algae
and some diatoms.

The liquid product of B. brunni reminds one of tar with a slight
benzine smell. There are solids like vaseline and other lubricants,
and since Engler obtained artificial petroleum from oleaginous algae
there would appear to be a possible source of petroleum in this type
of plant.

These observations of Zalessky are very interesting as throwing
new light on this subject, but it is doubtful whether he will con-
vince most observers that algae were the source of the bogheads.
It is peculiar that if these algae were so abundant during the for-
mation of the coal measures they have not been more frequently
recognized in coal deposits, while on the other hand it might naturally
be expected that in the open waters of almost every swamp a con-
siderable amount of such plant material should be laid down.

CHAPTER VII

FOSSIL FLORA OF THE COAL-FORMING PERIODS

Introduction

Plants are the source of all coal and therefore the types which
formed it and their distribution are matters of vital interest to all
who study the origin of coal deposits. The climatic conditions
existing during the coal-forming periods and the question as to whether
the plants of those periods were similar to those now living on the
earth are also subjects for special consideration. The fossil plants
are our best geologic thermometers and hygrometers and we are largely
dependent upon them for our information regarding the earth's
early climates.

In searching for plant fossils one seldom finds distinct forms in
the higher grade coal itself unless they are enclosed in " coal balls "
where they are almost hermetically sealed. The soft, semi-plastic
vegetal matter which forms the coal is partially destroyed by bac-
terial action and oxidation and then is squeezed so that little sign
of the original plants remains evident to the naked eye except that
in some cases a large fragment of a tree trunk may resist complete
destruction. In the coal balls the most delicate plant structures
may be preserved and aside from them the best fossils occur in the
shales and slates of the partings or in the roof or floor of the seam.
Delicate structures are sometimes preserved in these rocks, which,
being originally muds, have formed good coverings for the plants as
they have sealed them very tightly. In the coarser sandstones and
conglomerates only casts of the larger fragments of plants are pre-
served, due to two reasons, one the ready access of air and water to
the plant fragment, causing it to decay without leaving a good im-
print, and the other the coarseness of the material surrounding the
plant. This prevents the various particles of the plant from being
held in their proper position for the production of perfect impressions
of its structure.

A study of fossil plants satisfies us that, in many respects, the

178

INTRODUCTION

179

vegetation existing during the coal-forming periods was similar to
that now found upon the globe. The changes from the earliest
land vegetation to the modern types have, on the whole, been gradual
although a few sudden and marked changes have occurred. The
first great development of land plants, which made the formation of
coal possible, occurred in the Devonian period, and from Upper Dev-
onian time until the Pleistocene there was not a period in the earth's

FIG. 38. Lepidodendron lycopodivides, (Sternberg) showing branches
and leaves. (After Zeiller.)

history when coal was not fo ming somewhere on the earth. This
indicates that the formation or non-formation of coal during any period
since the first appearance of land plants has been fundamentally de-
pendent upon the topographic and climatic conditions then existing
on the globe rather than on the lack of plants or of any particular
kind of plant. There seems always to have been a flora ready to

l8o FOSSIL FLORA OF THE COAL-FORMING PERIODS

populate any region where conditions were suitable for development.
Everything points to the fact that it matters little what kind of plant
enters into the constitution of coal, but the physical and chemical
changes which the vegetation later undergoes produce the profound
differences in the different types of coal derived from it.

The Rise of the Land Plants

The two outstanding features in the evolution of the earth's
vegetation are the great development of the Pteridophytes, known
to many as the Vascular Cryptogams, in the early days of land plants,
and the advent of the flowering plants comparatively late in the
earth's history.

The Pteridophytes include the Filicales, or ferns; the Equise-
tales, or horsetails; the Lycopodiales, or lycopods, and the Spheno-
phy Hales. All of these were present in the Devonian and they reached
an extraordinary degree of perfection in the Carboniferous. The
ferns have continued to flourish through all the periods to the present
day, with the disappearance of many genera and the appearance of
new ones. The horsetails had representatives in the Carboniferous
which were good-sized trees, and they continued as such until the
end of the Jurassic when the last great trees of this type disappeared
and the group degenerated until it is now represented only by the
insignificant Equisetum.

The lycopods of the genera, Lepidodendron and Sigillaria formed
giant trees which were dominant in many of the coal basins. They
disappeared very early in the history of land plants, Lepidodendron
not even reaching the Permian and only a few species of Sigillaria
existing in the lower portion of that system. For the sudden ending
of these great genera in the Northern Hemisphere there is not much
explanation because there seems to be little evidence of a sudden
change in climate, although the prevalence of red beds and the pres-
ence of annual rings of growth in trees indicate approaching aridity
and more distinctly marked seasons. In the Southern Hemisphere
their extinction is more readily understood as it corresponds closely
with the inception of glacial conditions which practically wiped out the
previously existing flora and introduced the Gangamopteris flora
containing, as common forms, Gangamopteris, Glossopteris and
Rhacopteris. The latter flora has been an accompaniment of inter-

THE RISE OF THE LAND PLANTS
PLATE V.

181

A group of grains, cones, spores, and seeds from the Coal Measures of France.
Figs, i, 2, Male floral organs of cordaites; Fig. 3, Grains of pollen; Figs. 4, 5, 6,
7, Cordaianthus gemmifer; Figs. 8, 9, 10, n, 12, 13, 14, 15, Cordaianthus bacci-
fer; Figs. 16, 17, 18, Cordaicarpus major, ventricosus, vellavus; Figs. 19, 20, 21,
C. Guthbieri, ovatus, congruens; Fig. 22, Cordaicarpus punctatus, Gr.; Figs. 23,
24, 25, C. drupacens, expansus, reniformis; Fig. 26, C. eximius; Fig. 27, Diplotesta
Grand'Euryana (Brong.); Fig. 28, Carpolithes avellanus. (After Grand'Eury.)

182 FOSSIL FLORA OF THE COAL-FORMING PERIODS

glacial periods in Australia, India, South Africa, and South America.
All of these countries were more or less closely linked up in the Per-
mo-Carboniferous by land connections. This flora has also been found
to a limited extent in the Northern Hemisphere as, for example, in
European Russia which could be easily reached from India since the
Himalaya Mountains were not then in existence.

This change in the vegetation of the Southern and to a lesser
extent in that of the Northern Hemisphere is the most sudden change
in the history of plant life on the earth. In the coal fields of America
there was a great change in the vegetation during the Permian, as
every species, but not every genus, of the Coal Measure plants dis-
appeared early in that period. The increasing dryness and the ele-
vation of the Appalachian Mountain system had a profound influence
on the flora of the eastern part of the continent, which was the only
great land area at that time as most of the western portion of the
continent was under the sea. Many genera and some families ceased
to exist, and when the Triassic period opened the Gymnosperms
had become the dominant type of vegetation in place of the Pteri-
dophytes, or Vascular Cryptogams.

The Gymnosperms, or " naked-seed " plants were represented in
the Devonian by the Cycadofilicales, a group of seed plants which
strongly resembled some of the ferns in appearance but which bore
seeds and were similar to the cycads in some other respects. These
plants occupied a very prominent position in the Carboniferous period
and were for a long time mistaken for ferns. The Gymnosperms
were also represented by the conifers which appeared in the Devonian
and which left some traces in the Carboniferous. In the Permian,
Walchia and Voltzia were typical examples of this group, which be-
came much more prominent in the Triassic than it had been previously.
During the Jurassic some of our more modern types of conifers, like
the pine and the cypress, appeared and continued to flourish.

Another great Gymnosperm group was the Cordaitales which
appeared in the latter part of the Devonian period, became very
abundant in the Carboniferous and gradually died out before the
close of the Paleozoic. These plants were probably the ancestors of
the Gingkoales. The latter became abundant in the middle of the
Mesozoic era and then gradually declined until the group is now
represented by the single species, Gingko biloba. The cycads were

THE RISE OF THE LAND PLANTS

183

PLATE VI.

Lepidodendron aculeatum (Sternberg) showing the leaf scars and the varying ap-
pearance of these when portions of the bark are removed, i A is an enlargement of
one of the leaf cushions, and 7 illustrates the bark of an old tree. (After Zeiller.)

184 FOSSIL FLORA OF THE COAL-FORMING PERIODS

represented in the Coal Measures and they gradually developed to a
climax in the Jurassic. They have since declined in relative im-
portance.

From the Triassic, which seems to have marked the beginning of
the dominance of the more modern vegetation over that of the Pale-
ozoic, the flora has become more and more like that with which we
are now familiar. There were periods of adversity for the plants
and there were periods like the Jurassic and early Tertiary when the
climate seems to have been fairly uniform from the equator to the
poles. During these periods the tropical and subtropical species
spread far to the north and south as they did in the Carboniferous,
and the remains of plants like the cycads, which we now think of as
tropical and subtropical lie beneath the Arctic snows.

In the Triassic 1 the Gymnosperms were dominant but the flora
on the whole was not luxuriant as in the Carboniferous. The horse-
tails were large and abundant. There were many ferns and conifers.
The cycads were beginning to be numerous.

The Jurassic period showed a much greater development of modern
genera than did any previous period. The cycads reached their
climax and the period has been called the " Age of Cycads." Mod-
ern conifers like pines, arbor vitae, and cypresses appeared.

With the opening of the Lower Cretaceous, or the Comanchean of
America, an important event in the evo ution of plants occurred.
This was the appearance of the Angiosperms, or " enclosed-seed "
plants. These flowering plants, apparently originating in the north-
eastern part of the continent, soon spread all over it, and many modern
genera of eucalypti, figs, magnolias, cinnamon, and others well known
today, made their appearance and have contrived to flourish to the
present time. In the Upper Cretaceous the beech, birch, oak, wal-
nut, breadfruit, and holly were all present and the flora had assumed
quite a modern aspect.

Classification of Plan

In a classification of plants which includes foss'l types it should be
pointed out that the fossil plants must be divided into genera which
are founded on a basis different from that used in a classification of

1 Fontaine, W. M., Older Mesozoic flora of Virginia. U. S. Geol. Survey, Monograph
VI, 1883.

CLASSIFICATION OF PLANTS

185

living plants. This is owing to the incompleteness of the fossils
since parts of the plant may be separated from each other or entirely
destroyed. It is necessary to classify them into what may be called
" form " genera, based on the form of the fragment. For example,
the genus Lepidodendron includes the stem of a tree and Stigmaria
the root of the same tree. Such an arrangement of genera is not
found in the classification of living plants.

FIG. 39. Group of grains representing the seeds of various plants in the Coal Meas-
ures of France A, B, Trigonocarpus (Brong.); C, Polylophospermum (Brong.); D, E, F,
Polypterocarpus; G, H, Codonospermum (Brong.); I, Carpolithes sulcatus (Prest.);
J, K, L, M, Rhabdocarpus (Gopp and Berg). (After F. C. Grand'Eury, Flore Carbon-
ifere du Departement de la Loire.)

Many botanists have divided all plants into two large groups, the
Cryptogams or spore-bearing plants, and the Phanerogams, or flower-
ing plants. The former supposedly included all those in which the
sexual reproduction is concealed, thus embracing all the lower types.
In the Phanerogams the reproduction was thought to be exposed in
the stamens and pistils which were mistaken for sexual organs. In
this division were placed all the seed plants.

In more recent classifications, however, the seed plants are known
as Spermatophytes and they are divided into the Gymnosperms and
Angiosperms, the former comprising the primitive seed types and
the latter the more highly developed and more modern flowering
plants. As might be expected, the older fossil seed plants all belong

186 FOSSIL FLORA OF THE COAL-FORMING PERIODS

to the Gymnosperm group as do also many of the later fossils, and our
discussion of the coal flora will be confined largely to a discussion
of this group, as the Angiosperms did not appear on the earth, so
far as known, before the Cretaceous period. In a modern classi-
fication 1 of plants the following divisions are recognized: (i) Thal-
lophytes, (2) Bryophytes, (3) Pteridophytes, and (4) Spermatophytes.

(i) THE THALLOPHYTES

The Thallophytes are plants of the simplest form and they get
their name from the fact that with few exceptions they consist only
of thalli. The thallus is an undifferentiated vegetal body which in
its lowest form, like the animal amoeba, does not have a division of
functions. In such forms the jelly-like mass of protoplasm can push
out legs, or pseudopodia for purposes of locomotion and these may
surround particles of food which become engulfed in the mass and are
absorbed. The processes of reproduction are simple. In some
cases there is simple division, in others a spore is produced which
gives rise to the new plant. Some of the higher forms possess multi-
cellular sex organs.

There are two important divisions of the Thallophytes including
(i) Algae and (2) Fungi. The Algae are subdivided according to
color into the " Blue-Green," the " Green," the " Brown " and the
" Red " Algae.

The Fungi are subdivided into at least four groups which contain
respectively, the water moulds and the mildews; rusts and smuts;
the toadstools, mushrooms and puffballs; the bacteria and the lichens.

The Algae vary in size from microscopic organisms to the large
seaweeds, and many of the Fungi are so minute that they cannot be
seen with the naked eye.

From a palaeontological standpoint the Algae existed in pre-
Cambrian time and they have been abundant in certain geological
periods, although it is doubted whether they played any important
part in the formation of coal. Bacteria have also been in existence
since early geological time and their influence in coal formation has
been discussed in connection with the biochemical processes in the
origin of coal. It is believed that fungi such as mushrooms have also

1 Coulter. J. M., Barnes, C. R., and Cowles, H. C. A textbook of botany, Vol. I,
1910

CLASSIFICATION OF PLANTS

I8 7

PLATE VII.

i 4, Sigillaria elegans (Sternberg); 5 10, Sigillaria mamillaris (Brongniart).
These figures illustrate the different appearance of the specimens when portions of
the bark have been removed, i and 5 show the scars of the organs of fructification
as well as the leaf scars; 4 and 6 show the posterior side of the bark; 10 is from a young
tree. (After Zeiller.)

l88 FOSSIL FLORA OF THE COAL-FORMING PERIODS

been instrumental in producing biochemical changes in peat as far
back as the Carboniferous period. Any evidence of fossil Thallo-
phytes, so far as known, can be seen only by aid of the microscope and
therefore these plants do not concern the average person collecting
plant fossils.

(2) THE BRYOPHYTES

The Bryophytes are a large group of plants showing a distinct
advance over the Thallophytes in structure. They show a definite
alternation of generations and are characterized by sexual and sexless
individuals. The gametophyte produces the sex organs and the
sporophyte produces the spores. The members of the group possess
an archegonium which is characteristic of higher plants, and they thus
show their relation to these higher forms. They possess a multi-
cellular antheridium much more highly developed than that of the
Thallophytes.

This group is divided into two main divisions (i) Hepaticae or
liverworts and (2) Musci, or mosses, including the Sphagnales or
" bog mosses "; the Andreaeales; and the Bryales, or " true mosses."
The Bryophytes, or Bryinae are regarded by Land and others as of
recent origin although it has been claimed that barren forms of this
group have been found in the Carboniferous of France. They are of
little interest from the palaeontological standpoint but the Sphag-
nales, comprising the genus Sphagnum, are of much interest at the
present time because of the importance of this genus in the formation
of peat in the cooler climates.

(3) THE PTERIDOPHYTES

The group of Pteridophytes contains many important fossil species
in addition to numerous well-known living forms, such as ferns, horse-
tails and club-mosses. They are characterized by a vascular system,
or series of vessels for conducting material from one part of the plant
to another, and from this character they are frequently known as the
Vascular Cryptogams. This vascular system serves to separate the
Pteridophytes very sharply from the Bryophytes and Thallophytes,
but it is found in the Spermatophytes and shows the relation of the
Pteridophytes to these higher seed plants. The gametophyte, known
as the prothallium, and the sporophyte are independent of each other.

CLASSIFICATION OF PLANTS

189

The pro thallium develops from a spore and on it the oo spore develops
in the archegonium, giving rise to the sporophyte, the full-fledged

FIG. 40. i Sigillariostrobus goldenbergi. (O. Feistmantel.) ; 2 S. tieghemi (Zeiller);
4 S. goldenbergi (Zeiller); i, 2, 2 A and 4 show cones of fructification; 2 B and 4 A are
macrospores enlarged. (After Zeiller.)

plant, bearing spores in the sporangia. Most people are familiar
with the dark spots on the under side of fern leaves. Each of these
spots is a group of sporangia known as a sorus. It is considered that

FOSSIL FLORA OF THE COAL-FORMING PERIODS

the Pteridophytes have been developed from a liverwort-like an-
cestor.

This group has been subdivided by Coulter, Barnes, and Cowles 1
into six groups as follows: (i) Lycopodiales or club-mosses, (2)
Psilotales, (3) Sphenophyllales, including only the fossil genus Spheno-
phyllum, (4) Equisetales, or " horsetails," (5) Ophioglossales, in-
cluding the common adder's tongue and moonwort, and (6) Filicales,
or ferns, including the Filicineae or " true ferns " (homos porous) and
Hydroteridineae, or " water ferns " (heteros porous).

Zeiller 2 makes the following four divisions (i) Filicineae, or ferns,
(2) Rhizocarpeae, or Hydropterides, often placed as a sub-class under
the Filicineae, (3) Equisetineae and (4) Lycopodineae. Of these
(i), (3) and (4) are well represented among the Coal Measure fossils,
but (2) is absent unless Sphenophyllam be put in that class as some
have placed it, although it is more nearly related to the Lycopodineae.
It has no living representative.

(1) The Lycopodiales. There are several living and many ex-
tinct genera in this group. Lycopodium, which is the best known,
has been characterized by Coulter as possibly the best living repre-
sentative of the earliest forms of vascular plants. Some have re-
garded Phylloglossum, an Australian species, as the most primitive
Pteridophyte.

In Lycopodium the plant, or sporophyte, is a branching stem cov-
ered with many small leaves and on each of these there is a spo-
rangium on the upper side. The term sporophyll is applied to these
spore-bearing leaves and when grouped together they form a strobilus.
There is a tendency in some of these plants for the lower leaves to be-
come sterile and cease to bear sporangia, while this function is carried
on entirely by stalk-like sporophylls rising above the foliage leaves.

The stem shows two zones, an outer one of cells known as the cor-
tex and an inner one known as the stele in which the vascular system
is found. From the vascular cylinder, strands extend through the
cortex to form the leaf traces on the exterior.

The Lycopodiales, although now represented only by the humble
club-mosses, were in Carboniferous time among the large trees and
their fossil forms are as a rule arborescent.

1 Op. cit., p. 122.

2 Zeiller, R., Bassin houiller de Valenciennes, Description de la Flore Fossile, Text
and Atlas. Paris, 1888.

THE LYCOPODIALES

IQI

Two well-known families, Lepidodendrae and Sigillariae, are found
widely distributed in later Paleozoic rocks. Under the Lepidodendrae
several genera have been recognized: Lepidodendron (Sternberg),
Lepidopholios (Sternberg), Halonia (Lindley and Button), Bothro-
dendron (Lindley and Hutton), Lepidostrobus (Brongniart), Lyco-

FIG. 41. i Stigmaria ficoides (Brongniart) showing main roots and attached rootlets;
2 and 3, Scars where rootlets have been attached. (After Lesquereaux, Pa. Geol. Survey.)

podites (Brong.), Lepidophyllum (Brong.). Of these Lepidodendron
is best known and it will be described as a type.

Lepidodendron (Sternberg): Plants of this genus formed trees in
Paleozoic time which according to Grand 'Eury 1 reached a meter in
diameter and 30 meters in height, with leaves in some cases a meter
long. They and the Sigillariae are so abundant in the Coal Measures
and their stems are so characteristic that they have always attracted
a great deal of attention among miners and others collecting plant
fossils. Sigillaria is recognized by the parallel vertical lines of leaf

1 Grand'Eury, F. C, Flora carbonifere du Departement de la Loire et du Centre de
la France; Paris, p. 148. 1877.

1 92 FOSSIL FLORA OF THE COAL-FORMING PERIODS

cushions on the bark while Lepidodendron is distinguished from it by
its spirally arranged lines of leaf scars.

The leaves of Lepidodendron are generally acicular, and very long
on the stems, but much shorter on the branches; they diminish in
size with each bifurcation of the axis. On the stem they are attached
to elongated-rhomboidal to pointed-oval cushions, (Fig. 38). When
the epidermis is present these cushions show three bodies making up
one structure roughly oval in outline and sharply tapering at one end.
The other end is capped by a small rhomb with three small dots.
Above this rhomb, close to the end of the cushion, is a small scar
representing the leaf-detachment scar. The small dots are re-
garded by most writers as leaf-bundle traces, although some think
that only the middle one is of this origin. If the outer bark be re-
moved, a new condition is presented and each cushion shows only
one scar at the top. (Plate VI.)

The cushions are in contact with one another except that in some
specimens they are separated by sharp furrows and in others by broad
flat strips. According to Stur 1 who has given detailed descriptions
of these fossils, the former are older plants than the latter.

As to the reproduction of the arborescent fossil Lycopods, Zeiller 2
says that they appear to have been heterosporous. The greater
part of the cones of fructification in which the structure has been
studied seem to carry the macrosporangia on the lower and the micro-
sporangia on the upper bracts. He still feels, however, that the
matter has not been fully settled.

Geologic and geographic distribution: .Lepidodendron was widely
distributed over the earth in Carboniferous and sub- Carboniferous
time. It seems to have been found in every country where coal was
forming at that time, reaching its maximum development in the
lower and middle Coal Measures and then declining. In Australia
no trace of it is found even in the Permo-Carboniferous deposits
as it had died out before they were laid down, and in Europe it barely
extends into the Permian. In North America it has not extended

1 Stur, D., Die Culmflora der Ostrauer und Waldenburger Schichten. Abh. d. k. k.
Geol. Reichsanstalt zu Wien, Vol. 8, Heft II, also Die Culmflora des mahrisch-schlesis-
chen Dachschiefers, Heft I, 1877. Quoted by Solms-Laubach in Fossil Botany, Rev.
Trans, by Balfour, I. B., 1891.

* Zeiller, R., Op. cit.

THE LYCOPODIALES

193

into the Permian. 1 It is confined, therefore, to the Paleozoic. The
earliest appearance of the genus is reported to be in the Lower Dev-
onian beds of Wieda and Hartz. 2 It is widely distributed in America.

FIG. 42. 1-2 aa, Annularia longifolia (Brongniart); 2 b, 2 bb, A. inflata (Les-
quereaux); j, 30, Asterophyllites equisetiformis (Brong.); 4-50,, A. gracilis (Lesq.);
6, 7, Sphenophyllum schlotherinne (Brong.); 8, 9, Annularia sphenophylloides (Zenk.);
10, loa, Sphenophyllum bifurcatum. (After Lesquereaux, Pa. Geol. Survey).

Europe, and Australia in the Upper Devonian and the Mississippian,
or Sub-Carboniferous.

Sigillariaea: Under the family Sigillariaea have been described
the genera Sigillaria (Brongniart) 3 , Sigillariostrobus (Schimper), and
Stigmaria (Brong.). It has been known, however, since the work
of Binney that Stigmaria is not a genus but simply the root of
Sigillaria and Lepidodendron.

1 Solms-Laubach, Fossil botany. Rev. Trans, by Balfour, I. B., p. 194, 1891.

2 Fontaine, W. M., and White, I. C., Permian flora. 2nd Geol. Survey Pa., Pt. PP,
p. 114, 1880.

8 Solms-Laubach, Op. cit

194

FOSSIL FLORA OF THE COAL-FORMING PERIODS

Of the others, Sigillaria (Brong.) 1 is by far the best-known genus.
As already stated, it may be distinguished from Lepidodendron by
the fact that the leaf scars are arranged in vertical, parallel bands
rather than in spirals. Our knowledge of the leaves and many other
features is not as great as it is of those of Lepidodendron.

FIG. 43. Calamites suckowi (Brongniart) with articulations and secondary branches.
Coal Measures of France. (After Zeiller.)

The leaf cushions are roughly polygonal in outline and they may
be compressed vertically so as to give a transversely elongated six-
sided figure with the two horizontal sides considerably longer than
the other four, which are approximately equal. (Plate VII.) When
of this form they are compressed together so that they form vertical
ribs of scars alternating in adjacent rows.

Along the upper side of the cushion there are three small marks.
The middle is punctiform or somewhat elongated transversely, while
the others are short, thin marks diverging from it. These marks
represent the leaf traces.

1 Brongniart, A., Observations sur la structure interieure du Sigillaria elegans com-
pare"e a celle des Lepidodendron et des Stigmaria et a celle des vegetaux vivants. Ar-
chives du Museum d'Hist. Nat. Vol. I, 1839.

THE LYCOPODIALES

195

There is a good deal of uncertainty about the leaves of Sigillaria,
but leaves which are believed to be from these trees have been de-
scribed by a number of botanists. They are long and have a keel
resulting from the projection of the
median nerve. White 1 has found
leaves in the Missouri Coal Meas-
ures which he describes as probably
belonging to Sigillaria. They were
broad, rather thin, but seldom
flattened. Some fragments were
20 cm. long and 5 to n cm. in
width. They tapered very grad-
ually and, from the appearance of
certain fragments, the entire leaf
must have been 40 to 50 cm. in
length before being broken. The
upper surface showed a strongly
marked furrow 2 to 2\ mm. in
width. The lower surface of the
leaf was marked by a carene about
2 mm. wide and on either side of
this there was a well-defined crease,
probably the stomatiferous crease
previously described by Renault.

Dichotomous branching has been
found in this genus but stems are
frequently single.

In the matter of reproductive
organs it has been observed that
the regular bands of leaf scars are
frequently curved or irregular and
that lying between them there are other scars which are rounded or
angular and which differ considerably from the leaf scars. These
are supposed to be the scars left by the organs of fructification. Much
interest has been attached to Zeiller's 2 discovery of Sigillarian cones

1 White, D., Flora of the outlying carboniferous basins of Southwestern Missouri.
U. S. Geol. Survey, Bull. 98, p. 103, 1893.

2 Zeiller, R., Cones de fructification des Sigillaires. Ann. des Sci. Nat., Ser. 6, Tome
19, 1884.

FIG. 44. Calamites cistii (Urong-
(After Lesquereaux Pa. Geol.

196 FOSSIL FLORA OF THE COAL-FORMING PERIODS

on long stalks with the leaves bearing sporangia standing out from
the stem. Since he could only find macrospores he considers either
that these trees were homosporous, or that the two types of spores
were produced on different cones and the macrospore cones were not
found. The discovery of these cones has led some botanists, such as
Renault, to regard some of the Sigillariae as closely related to the
cycads, but such relation has not been substantiated.

Geologic and geographic distribution: Sigillaria did not make its
appearance in Europe before the beginning of the Carboniferous, and
very few specimens are found in the Millstone Grit. It seems to
have reached a climax about the middle of the Coal Measures and
then declined. The Rothliegende is probably the latest formation
in which remains are found. This family is not mentioned as oc-
curring in Australia or New Zealand and it seems to be considerably
more restricted geologically and geographically than Lepidodendron.
In North America only two species reach the Permian and they dis-
appear early in that period.

Stigmaria ficoides (Brongniart) : x The fossils known as Stigmaria
were in early days thought to be a genus of plants. They are ex-
tremely abundant in the " sea tear th " under the coal seams of many
fields, and the finding in England of these bodies actually attached to
stumps of Sigillaria and Lepidodendron has settled their derivation.
They are probably the roots of a few other genera also and it is in-
teresting to see how similar are the roots of so many of these trees.
The scars on the roots are the markings of the rhizomes or rootlets,
and specimens have been found with dichotomous branches (Fig. 41).
Very often these roots when broken open exhibit a cylindrical body
which readily separates from the exterior coating and which seems
to be a cast of the central cylinder.

(2) Sphenophyllales. The Sphenophyllales are not represented
by a living species. The only genus is Sphenophyllum (Brongniart) 2
which is well represented by fossils in the Coal Measures. There
has been much difference of opinion regarding its relations. Some

1 Renault, B., et Grand'Eury, Etude sur les Stigmaria, rhizomes et racines de Sigil-
laries. Annales des Sciences geologiques, Tome 12, 1881.

2 White, D., Op. cit., p. 35; Coemans, E. et Kick, J. J., Monographic des Sphenophyl-
lum d'Europe, Bull, de 1'Acad. Roy. d. Belgique, 2me Ser., Tome 18, p. 134, 1864; also
Newberry, J. S., The Genus Sphenophyllum. Jour. Cincinnati Soc. Nat. Inst. XIII,
p. 212, 1891.

SPHENOPHYLLALE3

197

botanists consider it as most closely related to the Lycopodiaceae
while others regard it as being more nearly related to Calamariae.
Members of this genus are herbaceous, the stems are simple or branched,
and the surface is canaled. The leaves are in verticils on the strongly
marked articulations and in groups of three. The leaves are sessile
as a rule but they may occur on pedicles. Those on the stipe are
different from those on the habetas.

FIG. 45. i, ia Sphenopteris subalata (Gein); 2, 2b, S. brittsii sp. nov.; 3-40,,
S. goniopteroides sp. nov.; 5, 50, S. hoeninghausi (Brongniart); 6, 6a, S. elegans (Brong.) ;
7, fa, S. larischi (Stur); 8-pa, S. tridactylites (Brong.). (After Lesquereaux, Pa.

Geol. Survey.)

The center of the stem consists of a triangular axis made up of three
vascular bundles. Exterior to these is a ring of large aqueous tubes
with lateral tangential growth.

The bark is thin, lacuneous and generally poorly preserved. The
branches are single on articulations. The roots are cylindrical and
the arrangement of the wood in them is much like that of the stem.

The sporangia are borne on the bracts at some distance from the

1 98 FOSSIL FLORA OF THE COAL-FORMING PERIODS

axis and are marked at the point of attachment by a small circular
umbilical depression. 1

Geologic and geographic distribution: In Europe Sphenophyllum
extends from the Culm to the lower Rothliegende and was a very
prominent genus in the middle and upper Coal Measures. 2 It is not
mentioned as occurring in Australia. In North America this genus
occurs from the lower Coal Measures to the Permian.

(3) Equisetales. The Equisetales, or horsetails, include the
order Equisetineae, which in turn includes the family Calamarieae.
This group, which formed a great arborescent flora in the Paleozoic,
is now represented by the single genus Equisetum, a genus of small,
insignificant plants preserving many of the characteristics of the
fossil trees and commonly known as scouring rushes.

Of the Calamarieae Renault states that these include all fossil
plants, either Cryptogams or Phanerogams, which present a cala-
mi toid stem, i.e., a stem of which the central part is occupied by a
relatively voluminous pith, its length being divided into a series of
similar articulations which may or may not be related to the articul-
ations of the sheath. 3 He would then divide the Calamarieae into
two divisions, the Equisetinees and the Calamodendrees. The first
would include the articulated plants containing only primary wood,
some of which reproduce by simple spores, i.e., are isosporous, like
the modern Equisetum, while others carry both microspores and
macrospores. As examples the genera Annularia and Asterophyl-
lites are cited, (Fig. 42). Catamites apparently belongs here also.
The second division includes those which have the secondary
wood more or less well developed and which in their organs of fructi-
fication more nearly approach the phanerogamic plants than do those
of the other division. Of the family Calamarieae, Calamites (Suc-
kow) (Fig. 43), and Annularia (Sternberg) are the best known genera.
Other genera are Pinnularia, Asterophyllites, and C alamo phyllites.

In these plants the surface of the stems, the roots and their branches
are marked by ribs and longitudinal furrows. The bark appears
smooth but little furrows may be found. In some species the furrows

1 Renault, B., Bassin houiller et Permian d'Autun et d'Epinac. Flore Fossile, Text
and Atlas, Fasc. IV.

2 Solms-Laubach. Op. cit., p. 343.
8 Renault, B., Op. cit., p. 60.

EQUISETALES

199

PLATE VIII.

Pecopteris (Asterotheca) abbreviata (Brongniart.) i, Illustrating the gradual
dividing of the pinnules near the inner end of the frond; j, 4 Fertile pinnules; 4 B
Spores enlarged 40 times. Coal Measures of northern France. (After Zeiller.)

2OO

FOSSIL FLORA OF THE COAL-FORMING PERIODS

alternate at the joints and in some they do not. The roots have an
organization similar to that of the stem and frequently the aerial
stems rise from articulations of the roots. The racines and leaves are
arranged in verticils at each node on the root, stem, or branch. The
leaves are simple and uninerved, sometimes free and sometimes in a
collarette along the stem and branches. Sporangiae, attached to the
borders of transformed leaves, are generally disposed in numerous
verticils connected and forming the cone.

FIG. 46. i Odontopteris alata (Lesquereaux) ; 2 O. brardii? (Brongniart) ; 3, 4 O.
sphenopteroides sp. nov.; 5, 6 O. subcrenulata sp. nov.; 7, ?a O. abbreviata sp. nov.;
8 O. aequalis (Lesq.) (After Lesquereaux, Pa. Geol. Survey.)

These plants are believed to be isosporous like the modern represent-
atives of this group.

Geologic and geographic distribution: Calamites and Annularia
seem to have made their appearance with the Carboniferous rocks,
although members of the Equisetales were present in the Devonian
formation and extended through that system and into the Permian.
They were extremely important in the Carboniferous and representa-

FILICALES, OR FERNS

201

tives of the Equisetales have continued to flourish through the geologi-
cal periods to the present day. They continued to form large trees
until the end of the Jurassic period, but in the Cretaceous they de-
generated into small plants. As well as having extensive geological
distribution these plants were. widely distributed in Australia, Asia,
Europe, and America

FIG. 47. Neuropteris heterophylla (Brongniart) showing the development of primary
and secondary pinnules. Coal Measures of France. (After Zeiller.)

(4) Filicales, or Ferns. As previously intimated, the Filicales
are divided into two groups, the Filicineae or " true ferns " which
are homos porous, and the Hydropteridineae or " water ferns," which
are heterosporous. The true ferns include such types as the royal
ferns, tree ferns, filmy ferns and ringless ferns. The members of the
group extend from the Devonian period to the present and some
of them were very prominent in the coal measures of various periods.

2O2

FOSSIL FLORA OF THE COAL-FORMING PERIODS

They may be arborescent or herbaceous, the height of some of the
arborescent varieties being as much as 20 meters.

The classification of the living ferns is based chiefly on the nature
of the sporangia. Zeiller 1 states that on this basis ferns may be
divided into two large groups, Leptosporangiae or the ferns proper,
and Eusporangiae or Marattiadiae. In the former group each spo-
rangium springs from only one epidermic cell and when it is ripe the

FIG. 48. i, 4, 5, 7, 9, 12 Neuropteris hirsuta (Lesquereaux) ; 2, 5, 6, 8, 10, n, N.
angustifolia (Brongniart). (After Lesquereaux Pa. Geol. Survey.)

walls are formed of only one layer of cells. In the latter sub-class
each sporangium proceeds from a subepidermal cell, and when mature
the walls are relatively thick since they are constituted of several
layers of cells.

In the case of fossil ferns it is generally necessary to follow Brong-
niart's system 2 and classify them according to the nature of the fronds

1 Zeiller, R., Bassin houiller et Permien d'Autun et d'Epinac. fitudes des gites
mine'raux de la France. Fasc. II, Pt. I, Flore Fossile, (FougSres) 1890.
* Brongniart, A., Histoire des vegetaux fossiles, 1828.

FELICALES, OR FERNS 203

and the nervation since the organs of fructification are infrequently
preserved. One of the striking features of all ferns is the highly
divided character of the leaves. The method of division has been
used as a means of classification by Brongniart and others, but that
system is not very satisfactory. The organs of fructification, or
sporangia, where preserved, are found on the under side of leaves and
form little globular sacs containing a considerable number of spores
which are set free by rupture of the wall of the sporangium. The
spores give rise to the prothallium, a vegetative apparatus which
carries both the male and female organs.

On the basis of the manner of attachment of the pinnules and the
nervation the ferns may be divided into the following six groups: 1

1. Sphenopteridae, in which the frond is finely divided and the

pinnules are small;

2. Pecopteridae with pinnules attached to the rachis for all their

width;

3. Odontopteridae with pinnules equally fixed to the rachis for

all their width but without the distinct median nerve;

4. Neuropteridae with pinnules generally quite large, rounded,

and often notched in the center of their base, attached at
only one point;

5. Teniopteridae with simple fronds, ribboned, much longer than

wide, the edges entire or feebly crenulated;

6. Dictyopteridae, including all forms in which the nervation

anastomoses and forms a more or less complex network in-
stead of remaining separate.

In cases where the organs of fructification have been found, a more
logical and genetic arrangement may be made, but the classification
has never been satisfactory.

Following unsatisfactory attempts to classify the ferns thus, re-
cent work by Grand'Eury, White, Kidston, Oliver and Scott has
shown that many of these plants are not ferns and that they should
be placed with the Gymnosperms as the most primitive of these
plants. For those plants which bear seeds and which had formerly
been called Cycadofilices because they combined in the stem the

1 Zeiller, R., Op. cit.

204

FOSSIL FLORA OF THE COAL-FORMING PERIODS

characters of ferns and cycads, Oliver and Scott 1 have proposed the
name Pteridospermae. In this group Zeiller 2 considers that there
should be placed several of the Sphenopteridae, some Pecopteridae
such as Pecopteris fluckeneti and Pecopteris sterzeli, probably all the
Alethopteridae comprising probably Callipteridium and Callipteris,
also all the Odontopteridae and Neuropteridae. He considers that
it would be easy to change the two last-named families but there is
much uncertainty about many of the others such as the Alethopteridae,

FIG. 49. Taeniopteris Newberriana sp. nov. From the Permian. (After Fontaine

and White, Pa. Geol. Survey.)

and that three groups might be made, including the Filicineae, the
uncertain forms and the Pteridosperms. In this division Zeiller
would leave with the ferns those plants whose fronds carried the fili-
coid fructifications but whose male apparatus is like that of the Pteri-
dosperms.

Geologic and geographic distribution: The ferns made their ap-
pearance in the early Devonian and reached a fairly high state of

1 Oliver, F. W., and Scott, D. H., On Lagenostoma Lomaxi, the seed of Lyginodendron.
Proc. Roy. Soc. London LXXI, p. 477, 1903. LXXIII, p. 4, 1904; also On the structure
of the Paleozoic seed Lagenostoma Lomaxi. Phil. Trans. Roy. Soc. London, Ser. B.,
Vol. 197, p. 193, Pis. 4 to 10, 1904.

2 Zeiller, R., Bassin houiller et Permien de Blanzy et du Creusot, Etudes des gftes
MinSreaux de la France, Fasc. II, Flore Fossile, Text et Atlas.

FILICALES, OR FERNS

205

development in that period. They increased in numbers 01 species
and in individuals in the Carboniferous and while none of the typical

FIG. 50. i Alethopteris serli (Brongniart) ; j, A. decurrens (Artes). These forms
illustrate the different forms of the pinnules in this genus. (After Zeiller.)

Carboniferous species extended beyond the Permian other species
of the same genera have occupied a prominent position in the world's
flora during the Triassic and Jurassic periods and still others have

206

FOSSIL FLORA OF THE COAL-FORMING PERIODS

carried the succession to the present time. They have been found
in probably every country in which plant remains are abundant

(4) THE SPERMATOPHYTES

The Spermatophytes include the two great groups of highly organ-
ized seed plants, the Gymnosperms and the Angiosperms. They are
often called Phanerogams or " flowering plants."

GYMNOSPERMS

The Gymnosperms include a great variety of plants, from shrubs
to large trees, and they have had representatives from middle Paleo-
zoic time to the present. They are characterized by their naked seeds

FIG. 51. Lonchopteris bricei (Brongniart) showing the terminal pinnules and the
changes occurring in the pinnules with maturity. From the Coal Measures of France.
(After Zeiller.)

in contrast to the Angiosperms which have the seeds enclosed. The
main groups of. Gymnosperms are (i) Cycadofilicales , (2) Bennettitales ,
(3) Cycadales, (4) Cordaitales, (5) Gingkoales, (6) Coniferales, and
(7) Gnetales. Of these groups the Cycadofilicales, the Bennettitales,
and the Cordaitales are all extinct.

(i) Cycadofilicales: As already mentioned in the discussion on

GYMNOSPERMS 207

ferns, there have been found during this century numerous plants
which were formerly thought from their frond character to be ferns
but which have been grouped together to form the Pteridosperms
because of the discovery of their seeds. They are believed to be the
most primitive of the seed plants, and from them the modern Gym-
nosperms developed. They show a transition between the ferns
and cycads and they differ from the ferns in having secondary wood.
This secondary wood is still a Pteridophyte character in some groups
although it is also a characteristic of the Gymnosperms. The micro-
sporangia are similar to those of the ferns but the macros porangia are
very different since an ovule is developed. As the members of this
group have been differentiated so recently and as there is so much
uncertainty about which genera and species should be placed with
the Pteridosperms and which with the ferns, it is impossible to state
definitely their geological range. They appeared at least as early as
the Upper Devonian, became extremely abundant in the Carbonifer-
ous, extended into the Permian and probably into the Mesozoic.

(2) Bennettitales and (3) Cycadales: Bennettitales is the name
applied by some botanists to a group of extinct Mesozoic plants which
are regarded as the ancestors of the living cycads. In his monograph
on the fossil cycads, Wieland 1 stated that in the opinion of Scott and
Zeiller the Bennettitales should not be regarded as a separate class
and that his work has verified the opinion of these botanists and his
own earlier expressed opinion. He had formerly believed that Cycad-
ales should include the existing families Cycadeae and Zamiae form-
ing the order Cycadaceae, and the extinct family Bennettiteae which
might have the rank of an order.

The living forms of cycads are tropical plants and they occur in
both the Eastern and Western Hemispheres. Common genera are
Cycas and Zamia.

The family Cycadeoideae or the Bennettiteae have been reported
from the Triassic, the Jurassic, and lower Cretaceous of America
and they have a similar range in Europe and Asia.

The representatives, such as Zamites, of the living families of
cycads have been found as far back as the Coal Measures. 2 They

1 Wieland, G. R., American fossil cycads, Carnegie Inst. of Washington, p. 236, 1906.

2 Renault, B., et Zeiller, R. Sur quelques cycadees houilleres. Comptes rendus de
Pacad. de Paris, 1886.

208

FOSSIL FLORA OF THE COAL-FORMING PERIODS

increased in numbers through the Permian and reached a maximum
development in the Jurassic which is often spoken of as the " Age of
Cycads." They have had a very wide geographical distribution.
(4) Cordaitales: The Cordaitales formed the main portion of the
arborescent Gymnosperm vegetation of the later Paleozoic. They
comprised rather slender trees which were of uniform size for 10 or
15 meters, but reached upwards of 30 meters in height and were
crowned by numerous branches. The genus Cordaites (Unger) may

FIG. 52. Cycadeoidea marshiana showing stages in fruit production as shown in
branching species. (After Wieland, American Fossil Cycads.)

be taken as the typical representative of the group. The leaves are
simple and are characterized by distinct parallel nervation, often
becoming complex. They resemble those of the Cycads in exhibiting
the characteristic mesophyll, and those of the Coniferae in the form
of the leaf, which is long, usually rounded at the outer end and narrow-
ing towards the base.

The stem and branches are provided with a large medullar sheath
cut by transverse diaphragms of the pith. There is a thick cylinder
of secondary wood.

In the structure of the ovule and the swimming sperms they re-
semble the Cycads and Gingkos which are the only living plants

GYMNOSPERMS

209

with these sperms. Their structure has been studied in detail by
Grand'Eury, and Renault, and to them chiefly we owe our knowledge
of the reproductive organs.

Geologic and geographic distribution: The Cordaiteae appeared in
the Devonian in America, 1 Europe and Australia. It seems possible

FIG. 53. Cordaites showing the leaves and organs of fructification. (After Grand'
Eury. Flore Carbonifere du Departement de la Loire.)

that they may have lived as early as the Middle Devonian. They
were abundant in the upper Coal Measures and continued into the

1 Dawson, J. W., On Fossil Plants from the Devonian Rocks of Canada. Quart.
Jour. Geol. Soc. of London, Vol. 15, 1859.

210

FOSSIL FLORA OF THE COAL-FORMING PERIODS

Permian, but it is not believed that they survived the close of the
Paleozoic.

(5) Gingkoales: This order of Gymnosperms is represented by a
single living species, Gingko biloba, found wild in China and culti-
vated by the Chinese and Japanese. The fossil forms of this group

FIG. 54. Walchia frondosa (B. Renault) showing small cones. From the Permian of
France. (After B. Renault, Bassin Houiller et Permien, Etudes des Gltes Min6raux
de la France.)

have frequently gone under the name of the Salisburias. They have
probably been derived from the Cordaitae and they were abundant
in the Mesozoic, being mentioned as occurring in the Oolite and the
Chalk of Europe, and in the Triassic and Jurassic of Australia. 1

1 Siissmilch, C. A., An introduction to the geology of New South Wales, pp. 164 and
175, 1914.

GYMNOSPERMS

211

(6) Coniferales: This group of plants is so well known at the
present day that they scarcely need a detailed description. They
are characterized primarily by their cones although other plants,
such as some of the Pteridophytes, may have cones of a certain kind.
Most of these trees are evergreens, as the pines, hemlocks, spruces,
and cedars but some, like the tamarack, are deciduous. Most of
them have needle leaves which are specially adapted to the rigors of
northern climates. The stem is a single, central stalk extending to
the top of the tree.

There are two families (i) Taxaceae and (2) Pinaceae. The mem-
bers of the former family usually have fleshy seeds and ovules freely

FIG. 55. Leaves of plants from the Glossopteris flora.
(6) Glossopteris. (c) Rhacopteris.

(a) Gangamopteris.

exposed and those of the latter family have dry seeds and ovules
concealed by scales.

The Pinaceae may again be divided into four groups well repre-
sented by living forms: (i) Abietineae, including pines, spruces,
hemlocks, firs, cedars, and larches; (2) Taxodineae, including Sequoia
and Taxodium (bald cypress common in our southern swamps);
(3) Cupressineae, including the arbor vitae, and the juniper; (4)
Araucarineae, including the Araucarian pines so frequently seen in
New Zealand.

Representatives of the Coniferae extend back into Devonian beds,
but it is not always easy to place the fossil forms in the groups men-
tioned above and, furthermore, the wood of the Coniferae may in

FIG. 56. Leaves illustrating the development of the modern types of plants in the
later geological periods, a, Macro taenopteris magnifolia (Rogers), Triassic coal
beds of Virginia (Fontaine); b, Gingko digitata (Herr), Jurassic; c, Cinnamomum
Lesperium (Knowlton); d, Aralia veatchii and e, Rhamnus? Williardi (Knowlton), Upper
Cretaceous; /, Fagara, catahoulensis major (Berry) and g, Ulmus floridana (Berry),
Oligocene; h, Quercus chapmanifolis (Berry), Miocene (U. S. Geol. Survey.) 212

THE ANGIOSPERMS 213

some cases be confused with that of the Cordaites as there is a close
relationship between the groups, Cordaites and Coniferae. The
Taxaceae do not seem to have extended backward beyond the Jurassic.
The Cupressineae have been found as far back as the Jurassic. The
well-known extinct genus Voltzia probably belonged to the Araucar-
ineae and extended back into the Permian. Walchia is a conifer from
the Permian. The Sequoias have been found from the early Cret-
aceous onward and were abundant in the early Tertiary. Taxodium
probably extended from the Oligocene to the present. The Coniferae
have been widely distributed over the globe.

THE ANGIOSPERMS

This great group of plants, representing the climax in plant evol-
ution, was ushered in with the Cretaceous period. They have de-
veloped so rapidly and they now occupy such an important and com-
mon place in the living vegetation that any attempt to describe them
here would be futile. Their representatives are found in every
formation where plant fossils occur since the beginning of the Lower
Cretaceous period, and they now outnumber the Gymnosperms several
hundred times. The common trees, outside of the Conifers, belong
to this group, as do the grasses and the other common flowering plants
with which everyone is so familiar.

CHAPTER VIII
STRUCTURAL FEATURES OF COAL SEAMS

Thickness of Seams

Coal beds vary from a fraction of an inch to the enormous thickness
of 266 feet. At Morwell, Victoria, Australia, there are three seams
of brown coal which are 266, 227, and 166 feet respectively, in thick-
ness. They are the thickest so far known in the world. A drill
hole 1010 feet deep passed through 780 feet of coal. Other notable
beds are the Grande Couche of Commentry, central France, which is
60 feet thick, and the Mammoth seam of the anthracite region of
Pennsylvania, which in the Southern Field reaches 50 feet in thick-
ness. Seams in Styria and Manchuria exceed 100 feet in places.
Most seams vary rather rapidly in thickness from place to place, the
Pittsburgh bed of the Appalachian province being probably the most
remarkable exception to this rule. This seam has been traced over
an area of more than 2100 square miles with an average thickness of
over 7 feet. Its total original area has been estimated at about
30,000 square miles. The irregularities in the thickness of seams are
due chiefly to the structures known as " partings," " pinches " or
"squeezes/' " swells," " horsebacks," "rolls," "clay veins" and
" cut-outs " and to igneous intrusions.

Partings. A seam may be divided into several thinner seams or
" splits " by partings of clay, shale, slate, or sandstone, (Fig. 57).
For example, the Mammoth seam, which reaches a thickness of 50
feet in the eastern part of the Southern Field is divided into three
splits at the western end, averaging about 10, 12 and 15 feet respec-
tively, in thickness, with partings of slate between them running from
10 to 30 feet in thickness. These splits would be regarded as indi-
vidual seams were it not for the fact that they can be traced into the
main seam to the eastward. Other seams are known in which the
number of splits is very much larger than in the case cited.

The splits are due to the fact that while the vegetal matter is being
laid down in the swamp or open body of water there are periods

214

PINCHES 215

when clay or sand is brought in by water from the surrounding lands
and carried out over the vegetal matter. The deposit of sediment
grows thinner as it extends away from the dry land and some distance
from the edge of the basin the deposition of vegetal matter goes on
without interruption so that a continuous coal seam results, whereas
closer to the edge the seam is interrupted by these bands of sediment.
The number of partings will depend upon the rate of change in level
between the surrounding land and the basin, or upon the variations
in climate. A sinking of the basin where the vegetal matter is being
deposited or a rise of the surrounding land will cause sediment to be

FIG. 57. Diagram illustrating: C, cut-out; H, horsebacks; P, parting; R, roll;

S, split; V, clay vein.

carried out by streams farther from the edge of the swamp or other
basin than it was formerly, while a change to a wetter climate may
also cause greater erosion of the land and consequently a more ex-
tended deposition of sediment over the vegetal matter in the swamp.
" Pinches " or " squeezes," and " swells." These are terms
applied to sections in the seam where it has become constricted by
the squeezing in, or extended by the bulging out of the overlying or
underlying rocks. They are due to pressure applied to the seam during
the folding and other movements of the enclosing strata and they
may accompany the formation of " horsebacks " and similar struc-
tures.

2l6

STRUCTURAL FEATURES OF COAL SEAMS

" Cut-outs." This is a term applied by miners to any place in
the seam where the coal ends abruptly on account of faulting, squeez-
ing, or erosion. It may be used in a more restricted sense for the
case where part of the bed has been removed by erosion, (Fig. 57).
It often happens that a coal-bearing formation suffers erosion and a
stream cuts a ravine through one or more beds of coal. This ravine
may be filled later by sand or clay carried in by the stream, or a
glacier passing over it may fill it with drift consisting of a mixture
of clay, sand and boulders. A fine example of the latter phenomenon
is found in the Anthracite Field of Pennsylvania. Before the glacier
appeared in this district the Susquehanna River flowed in a channel

FIG. 58. Gorge of Des Moines River at city of Des Moines illustrating how a cut-
out may develop. (From Iowa Geol. Survey.)

between Nanticoke and Pittston. During Pleistocene time the
glacier moved southward across this channel, which became filled
with glacial drift. The river was thus forced to carve out a new
channel for itself after the glacier melted away. It has also been
suggested that this abandoned channel might have been gouged
out by the glacier as fiords are deepened. The old channel has
been well outlined as it has caused much trouble in mining, owing
particularly to the large amount of water contained in the sand and
gravel and the bad condition of the rocks along its edges.

" Horsebacks," ' 'rolls," and "clay veins." All of these
names have been used more or less loosely for the same structures
in coal mines in different localities. The term " horseback " among
the coal miners is used to indicate some foreign body in the coal
seam in much the same general way as " horse " is used among the
metal miners to indicate a mass of rock in the lode. It probably

HORSEBACKS 217

arose from the general rounded form, which is more or less charac-
teristic of these structures and which suggests the arched back of a
horse. The German miners use the word " horst " in much the same
way as " horse " is used among the miners in this country.

The names " rolls " and " swells " are very appropriate terms for
these structures because in some mines these masses of rock resemble
nothing more closely than the waves on the sea when running as a
ground-swell. The reason for confusing the " clay vein " with the
horseback is doubtless due to the fact that the former in many places
is an offshoot from a rounded mass of clay similar to a typical horse-
back, (Fig. 57).

Several theories have been offered to explain the origin of horse-
backs and it is possible they have been formed in at least two ways.
One theory, advanced by mining men in some coal fields, is that
they were formed by streams flowing into the swamps where the
vegetation giving rise to the coal was being laid down. 1 These
streams would bring in clay or sand and build up long narrow ridges
of sediment which would become buried under vegetal matter as
the formation of the coal bed progressed. The rolls in the roof are
explained as due to a stream cutting a channel down into the coal
seam, this channel later becoming filled with sediment. While this
explanation may account for a few of these structures it will not
account for the great majority of horsebacks, as they are undoubt-
edly due to compression of the seam and enclosing rocks, which pro-
duces small folds in either the roof or floor of the seam or in both.
When pressure is applied to the floor it buckles up into the coal, which
is less resistant than the bottom rock and, in the early stages of its
development, much more plastic than the underlying rocks. Like-
wise when pressure causes the draw slate to buckle in the roof of the
seam it bends down into the coal (Fig. 57). A very fine illustration
of the occurrence of these structures is seen in the Pittsburgh seam
in the vicinity of Connellsville, Pennsylvania. 2 They rise from 6
inches to as many feet above the general level of the floor of the seam
and resemble waves spread over the floor of the mine (Plate IX).
The seam is everywhere constricted above them except in one or two

1 J. F. Blandy, On evidence of streams during the deposition of the coal, (horse-
backs). Trans. Amer. Inst. Min. Eng., Vol. 4, p. 113, 1875.

2 Moore, E. S., "Horsebacks" in Oliver No. 3 Mine. Coal Age, Vol. 3, p. 566, 1913.

HORSEBACKS 219

places noted, where the roof slate is bowed up above the elevation
in the floor. The rolls often show lamination in the sediments where
the beds have been bent and in many of these there are bunches of
pyrite crystals which have collected there because the structure direc-
ted the circulating, iron-bearing waters into these little anticlines.

The horsebacks are not uniformly distributed over the floor of the
mine because the rocks are not uniformly resistant and therefore they
buckle in some areas and resist buckling in others. Where there is
one roll there are usually two or more adjoining it, as in the case of
waves on water, due to the fact that a large anticline should normally
have small ones on either side where it dies out. These smaller folds
result from irregularities in the strength of the bed and from the differ-
ent angles at which the force is applied as the larger fold develops.
That these structures are not deposits made by streams is proven
by the fact that they often occur entirely away from the border of
the swamp in which the coal vegetation was laid down.

The coal basins as they now exist are not identical in size or shape
with the original basins but have resulted from the folding of the coal
measures into anticlines, where there were originally small elevations,
and synclines, where there were originally small depressions in the
strata. With subsequent erosion of the anticlines the synclinal basins
have been separated from each other. Thus it will be seen that one
of these basins may be near the center of the great swamp in which
the vegetal matter was originally laid down and the horseback may
show no connection with the land at the border of the original basin.

It is evident that a direct relation may be found between the orient-
ation of the horsebacks and the direction of the main structures of
the basin. Following the general principles of structural geology it
is known that if a small fold occurs on the flank, in the trough, or on
the crest of a larger fold the axis of the minor fold will be in the same
direction as the strike of the rocks at that particular point in the larger
fold. It was found to be true at Oliver No. 3 mine, mentioned above,
that the axes of the horsebacks follow the strike of the rocks forming
the larger basin at the point where they occur, and inquiries in various
other mining regions where horsebacks are common elicited answers
which go to strengthen this assumption for the arrangement of these
structures in all fields. According to this principle the long axes of
the horsebacks in a pitching synclinal basin would form, if plotted on

220 STRUCTURAL FEATURES OF COAL SEAMS

a map of the basin, an elliptical zone around the deepest point in the
basin. As the center of the basin is approached the arrangement of
the structures will become much less regular owing to the confusion
of forces which are acting from various directions on the rocks in the
center of the basin. The establishing of this relationship between the
direction of the horsebacks and the larger folds in the coal basins has
a practical bearing. It should become possible, as our knowledge of
these structures increases, to predict the general direction in which
the long axes of the horsebacks will lie and, when the arrangement of
these is known, the entries and butts in the mine may be planned in
such a way as to avoid as much as possible the cutting of these ridges.
If one must be cut it may be cut along its shorter axis.

A " clay vein " is a body of clay which fills a crevice in a coal seam,
(Fig. 57). It is usually roughly tabular like an ore vein, but in
many cases it branches in an extremely complex manner, sending
stringers out in all directions through the coal. It originates where
the pressure on the floor or roof of the seam, or on both, is sufficiently
great to force plastic clay into small fissures and in many cases en-
large them. The clay often rises as a mound on the floor of the seam
so that it resembles a horseback and if there be a crack in the overlying
coal it rises from the mound as a vein. In some localities the miners
use the word " spar " for a small clay vein.

"Bell," "pot," "kettle." The terms "bell," "pot," and "kettle"
are often used for a roughly cone-shaped or rounded mass of slicken-
sided rock which falls from the roof of a seam, sometimes causing
serious accidents to the miners. These bodies are also known as
" camel-backs " and " tortoises." They are, in most cases, con-
cretionary structures containing pyrite, iron oxide, iron carbonate or
calcite mixed with clay or slate and they separate rather freely from
the roof slate. This ready separation is apparently often due to
previous movement in the strata as the bodies frequently show
slickensided surfaces indicating that there has been slipping of the
surrounding rocks over the concretionary masses. In addition to
the concretionary bodies which form these structures in the roof there
are certain harder or denser patches of clay or sandstone, which
separate from the adjacent rocks and fall from the roof, (Fig. 59).
Rounded masses of igneous rock and casts of trees occur in the upper
part of the coal bed in some regions and they fall freely from the roof.

FOLDING IN COAL BEDS

221

These structures may all go under the names mentioned above if
their shape, in the opinion of the miner, happens to correspond to
that of any of the above-named bodies.

FIG. 59. Small coal stringer, Paradise Mine Duquoin, 111. (From Bull, of the 111.
Geol. Survey, University of 111. and U. S. Bur. of Mines.)

Folding in Coal Beds

In any study or discussion of folds two terms, dip and strike, are
much used. The dip is the angle which the bed makes with a hori-
zontal plane, or in other words the inclination of the bed to a hori-

FIG. 60.

zontal plane. The strike is, in general terms, the direction of the
outcrop, but in many cases a more accurate and concrete definition
is necessary for practical purposes since the strike must sometimes

222

STRUCTURAL FEATURES OF COAL SEAMS

be determined in the bottom of a mine shaft or elsewhere where only
a very small area of the stratum is exposed. In such cases the strike
is represented by a horizontal line on the face of the bed or in other
words the strike is the line along which the bed intersects a horizontal
plane. This line may be found by using a clinometer or level and its
direction may be determined with a compass. The direction of
dip is always at right angles to the direction of strike, (Fig. 60).
The pitch is the inclination of the axis of a fold to a horizontal line.
The pitch and dip correspond at the extreme ends of a pitching anti-
cline or syncline, but in no other portion of the fold. Among miners
the term pitch usually refers to the inclination in the opposite direction
from that of the dip. It may be expressed as " up the dip."

Outcrop of Coal Seam

FIG. 61. Stereogram of a pitching syncline showing the relation between pitch and

dip in the coal seam.

A fold is a flexure in rocks, and it usually consists of two sections,
the anticline, or crest, and the syncline, or trough, of the wave-like
structure. The axis or the central line of the anticline or syncline is
never horizontal for great distances but bows down at the ends in the
anticline and up at the ends in the syncline, giving pitching anticlines
and synclines, (Fig. 61). This explains why a coal bed " cropping "
around the edge of a basin forms a sort of ellipse. Folds may be
closed or open. In an open fold the limbs, or the beds on the sides
of the flexure, are not squeezed together, while in the closed fold they
are. An isoclinal fold is one in which the limbs are parallel to each
other. An overthrust fold is one in which the beds are bent beyond the
vertical position and such a fold may grade into a thrust fault where
the compression becomes sufficiently great to break the rocks and
push them along the fracture. A monoclinal fold is one in which

FOLDING IN COAL BEDS

223

the beds dip in one direction only within a given area. When
a number of small, or secondary anticlines occur on a large anti-
cline the structure is known as an anticlinorium, and if small
synclines occur on a large syncline the resulting structure is a syn-
clinorium.

Folding has a great influence on coal seams, in pinching them off
as in horsebacks, bulging them out, and squeezing them so that in
some cases they are partly turned into graphitic carbon. The pres-
sure is less in the crest of an anticline than in the sides, therefore the
coal and soft rocks like clay are crowded into the anticline and the

FIG. 62. A sketch by W. R. Crane of an anticline in Alaska, in which the coal seam
has been pinched off on the limbs of the fold and crowded into the crest of the anti-
cline where the pressure is least.

seam becomes thicker in the crest but thinner on the limbs, (Fig.
62). Where the folding is intense there is always considerable
slipping of beds over one another, and the folds pass over into faults
if the movement becomes intensive. It is the heavy, strong beds or
so-called competent beds in a formation, which always control the
folding as they compel the softer and weaker beds to fold themselves
into such forms as they may under the circumstances. Cases are
even known where a certain bed has been highly folded although it
lies between other beds which show very little evidence of folding.
The latter beds must have slipped over each other and thus relieved

224

STRUCTURAL FEATURES OF COAL SEAMS

the pressure without crumpling, while the former was compelled to
wrinkle up to accommodate itself to the new conditions. An inter-
esting example of this in the English coal fields is pointed out by
Strahan (Fig. 63). This may have a bearing on the origin of an-
thracite in showing that the lack of crumpling in the strata adjacent
to the coal does not always prove the absence of great compressive
stress in the coal.

SCA'LE IN FEET

FIG. 63. Contortion in a parting between two coal seams leaving the beds above
and below apparently unaffected. Tir-bach. (After Strahan, Geol. Survey of England
and Wales.)

Faults

A fault is a fracture in the earth's crust along which the rocks on
one side have moved relatively to those on the other side. There are
three relative movements which may occur: (i) The rocks on one
side of the fracture may remain stationary and those on the other
side move up or down. (2) Those on one side may move up and the
others down. (3) The rocks on both sides may move in the same
direction but those on one side must move more than those on the
other before a fault results. The movement may also be along hori-
zontal or oblique rather than along vertical lines.

FAULTS

225

Certain names are used to designate the various real and apparent
motions in a fault. The fracture along which the slipping occurs is
usually called the fault-plane but the term fault surface is a better
word because the fracture in many faults departs widely from a plane
and it is sometimes a regular curved surface. The term displacement
is used in a general way to describe the relative movement of the
rocks on this surface whether the movement
be in a horizontal, a vertical, or an oblique
direction. In Fig. 64, EF is the displacement.
The vertical distance ED the beds are dis-
placed, is called the throw, the horizontal
distance FD the heave. The angle FED,
which the fracture makes with the vertical is
the hade. When the rocks on the upthrow
side of the fracture project above those on
the downthrow side this projection AC is known as the fault scarp.
During the movement on the fault surface the rocks are often smoothed
and polished. This smooth surface is a slickenside and when clay
results from the grinding up of the rocks during movement it is called
gouge, or selvage. If the rocks along the fracture are broken up into
angular fragments the resulting material is known as a fault breccia.

There are two main types of faults: (a) the gravity or normal
fault, and (b) the thrust fault. In the former the overhanging side

FIG. 64. Diagram illus-
trating a thrust fault and
fault nomenclature.

FIG. 65. Sketch of faults in main entry near parting. Southern Coal, Coke and
Mining Co., Mine No. 7, New Baden, Clinton County, 111. (From Bull, of the 111.
Geol. Survey, University of 111. and U. S. Bur. of Mines.)

or hanging wall side has moved downward towards the center of
the earth as a result of tension or stretching in the earth's crust, and
in the latter the overhanging side has moved upward relatively to
the other side as a result of compressive force. Igneous activity
may sometimes exert an upward pressure and produce thrust faults.
Figure 65 is an example of a normal fault and Figure 64 of a thrust

226

STRUCTURAL FEATURES OF COAL SEAMS

fault. There are also various names used by the miners to indicate
the nature of faults such as " shove " fault and " slip " fault. In
the former, one body of rock has been pushed into another and the
latter term is frequently used for a fault which lies nearly parallel
to the bedding.

In many coal fields faults are a source of great difficulty to the
miner, but other fields are almost entirely free from them. In some
faults the seam is only thrown a few feet but in others the displace-
ment may be several thousand feet. Thrust faults show the greater
maximum displacement and this may reach many miles in the large
mountains. It may be considered a general rule that the faults in
any particular basin will be practically all normal or all thrust unless
it can be shown that they have originated during at least two distinct
periods of faulting.

(B)

FIG. 66. Diagrams showing how in (A) a drill hole may pass through the same coal
seam twice because of thrust faulting and in (B) it may miss the seam entirely in the
gap resulting from normal faulting.

The effects of faulting on prospecting are very great. A concealed
seam may be brought to the surface or a seam at one time exposed
may be faulted and eroded so that it no longer comes to the surface.
A seam may be duplicated by faulting so that a drill hole will pass
through it twice, (Fig. 66 (A)) or a gap may be produced so a drill will
pass between the two portions of the seam without indicating its pres-
ence, (Fig. 66 (B)). If a fault cuts transversely through a syncline the
outcrops of the seam on the sides of the syncline after erosion has
occurred will be closer together on the upthrow side of the fault than
on the downthrow side, while the opposite will be the case if the fault
cuts an anticline.

It should be borne in mind that the older rocks will always be ex-
posed on the upthrow side of the fault if the area has been eroded since
faulting. In very few cases are faults so recent that the faulted rocks

UNCONFORMITIES

227

have not suffered erosion and in most cases all evidence of the fault
scarp has been removed. There is usually, therefore, little evidence
of the presence of the fault on the surface unless there be a marked

FIG. 67. A large fault in the Coal Measures near St. Etienne, France. (Photo by

E. S. Moore.)

difference in the rocks on opposite sides of the fracture. In some
places a sandstone may be brought opposite a shale, a shale opposite
a limestone or a non-fossiliferous rock may be brought into juxta-
position to a fossiliferous rock, or
a sedimentary rock to an igneous
rock. There are many features
which may be used by the geologist
to distinguish the rocks on opposite
sides of a fault and thus detect its
presence.

FIG. 68. Diagram illustrating a great
unconformity by folding, erosion and
subsequent deposition.

Unconformities

An unconformity is an interrup-
tion in the continuous deposition
of sediments in any locality. The

presence of this hiatus, or break may be indicated by one or more of
a number of factors among which are the following: (i) A sudden
change in the character of the fossils found above or below the

228

STRUCTURAL FEATURES OF COAL SEAMS

horizon where the unconformity occurs; (2) Folding or faulting of
the rocks below the unconformity while those above remain un-
disturbed; (3) Erosion of the underlying rocks before the later rocks
were laid down upon them. This is illustrated in Figure 57 where the
cut-out occurs. In Figure 68, the effect of both folding and erosion
is seen, as the coal-bearing formation was folded and eroded before
the later formation was laid down.

Igneous Intrusions

In regions of igneous activity such as those of the western states,
Alaska, parts of Great Britain and some other countries, the coal
seams have been cut by igneous intrusions of many forms. The

FIG. 69. Diagram illustrating the different forms which igneous rocks may assume
in intruding coal measures. B, a portion of a batholith; D, dike; L, laccolith; and
S, sill. Such intrusions produce natural coke and otherwise alter the coal adjacent
to them.

different forms which these intrusions take are illustrated in Figure 69.
If a fracture becomes filled with liquid rock it is known as a dike', if
the liquid spreads out along a bedding plane in the sediments and
solidifies as a tabular mass of great areal extent compared with its
thickness it is known as a sill. If it forms a lens-shaped body and
arches up the overlying strata it is a laccolith, while a large, irregular
mass is a batholith. Other bodies which have great vertical dimensions
compared with their lateral, are known as bosses, necks or plugs and

CONCRETIONARY BODIES IN COAL SEAMS

22Q

if the liquid rock reaches the earth's surface and flows out over the-
surface it is a lava flow, or sheet.

Some of the intrusions in coal seams are extremely complex in form.
A good example is that figured by Jukes from the South Staffordshire
Coal Field in England, (Fig. 70). Intrusions of less complexity may
be seen in the Newcastle Field of Australia and in some of the western
states. As a rule the dark basic rocks, such as traps, are capable of
producing more complex intrusions than are the lighter-colored, acid
rocks like granites because the liquid is less viscous and it more readily
enters intricate fractures.

T = Trap ; C = Coal ; S = Sandstone ;

SCALE 20 FEET = 1 INCH

FIG. 70. Complex intrusion in coal seam. (After Jukes, Geol. Survey of

England and Wales.)

The most important effects of igneous intrusions outside of the
difficulties they often create in mining operations is the coking of the
coal. (For a discussion of this subject see Carbonite or Natural
coke.) A dike usually affects a very limited area but a large sill
or laccolith may extend for a long distance parallel to a seam, con-
verting practically the whole bed into coke, as some of the sills have
done in Colorado and New Mexico. There is usually a relation be-
tween the thickness of the igneous body and the thickness of the coked
zone, one being directly proportional to the other, but this relation
will not always hold any more than it does in the case of the width of
the metamorphosed zone adjoining intrusions in other rocks. The
temperature of the molten rock, its gas content and other physical
conditions at the time it reaches the coal have great influence on its
coking effects.

Concretionary Bodies in Coal Seams

The concretionary bodies found in coal and in the adjacent rocks
commonly go under the names of " coal apples," " coal balls," and

230 STRUCTURAL FEATURES OF COAL SEAMS

" sulphur balls." The coal apples, or coal balls consist chiefly of
calcium carbonate, magnesium carbonate, iron carbonate, or iron
oxide, with varying amounts of clay, shale or sand. Small amounts
of calcium phosphate, carbonate of manganese and other constituents
are often present. The sulphur balls consist of iron sulphide (FeS 2 )
in the form of pyrite often known as " fool's gold " or marcasite,
mixed with clay or sand in different proportions. In some cases a
little free sulphur occurs as a coating owing to oxidation of the pyrite.
All these bodies are concretions in the strict sense of the term. They
have grown up as a result of the chemical deposition of these various
substances around some central point and they show a concentric
arrangement of the material varying very greatly in degree of perfec-
tion. They are irregularly distributed through the coal seam, or the
shales above and below the coal, or they project from the coal into
the adjacent rocks.

In addition to these concretions there are other bodies consisting
of coal, which strongly resemble concretions in appearance but which
are not true concretions since the material composing them has not
been precipitated from solution around a nuclear point. They re-
semble somewhat the so-called " physical " concretions of some writers
as distinguished from chemical concretions, and they are believed to
have been formed as a result of fracturing and movement in the bed.
This type is common in Colorado where the coal is known as " nigger-
head " coal.

Calcareous concretions. These bodies are abundant in the Coal
Measures where limestones are associated with the coal-bearing for-
mations. They have been described in detail by S topes and Watson 1
for the coal fields of England and some of the Continental fields.
They occur in large numbers in those coal seams, the roofs of which
contain a marine fauna consisting of goniatites and lamellabranchs.
The waters in which the vegetal matter forming the seams was laid
down were rich in salts of calcium and magnesium. The roof shales
contain plant remains which differ considerably from those in the coal
seams, thus suggesting that the vegetal matter in the overlying rocks
was drifted to its present location while that which composed the seam

1 Slopes, M. C., and Watson, D. M. S., On the present distribution and origin of the
calcareous concretions in coal seams known as "coal balls." Phil. Trans. Roy. Soc.
London. Series B, Vol. 200, pp. 167-218, 1909.

CALCAREOUS CONCRETIONS

231

FIG. 71. Vertical dike in Coal Measures, Australia. (Photo by E. S. Moore.)

FIG. 72. Peculiar effects of shearing in coal. Specimen in Museum National d'
Histoire Naturelle, Paris From Northern France.

232

STRUCTURAL FEATURES OF COAL SEAMS

Eugene

100 metres North of Shaft No.l

SECTIONS OF THE HOOK OF
EUGENE AND LOUIS

Section North of
Shaft No. 1

Louis

400 metres East and

100 metres South of

Shaft No.l

FIG. 73. Very complicated structures resulting from faulting and squeezing in the
coal seams of Northern France. The dark areas are sections of the seams. (From
the Publications du Service des Topographies Souterraines; Bassin Houiller du
Pas-de-Calais.)

CALCAREOUS CONCRETIONS 233

grew in place. This might be the result of the deposition of plant
remains in brackish water along the sea coast followed by a trans-
gression of the sea over this material with the deposition of marine
fossils in calcareous strata. Jeffrey 1 considers that the coal balls
indicate that the vegetal matter enclosed in them was transported
rather than developed in situ because he has found fragments of char-
coal associated with other remains of plants in the same concretion.
The material in the concretions differs from ordinary coal in the ab-
sence of the large proportion of spores which are found in the latter.

These " coal balls " almost everywhere contain remarkably well-
preserved plant remains, indicating that they were formed about the
time the plants settled to the bottom of the body of water and before
they had an opportunity to decompose and become macerated. It is
not necessary, as some writers have suggested, to invoke the preserva-
tive properties of saline water to account for their preservation. The
perfect sealing conditions provided by the accumulation of mineral
matter above the plant have been responsible for their complete
preservation, and the finer structures of the plants may often be rec-
ognized in these concretions when they are not preserved at all in the
adjacent coal. In some cases a plant stem may extend out into the
surrounding coal. A concretion may be partly in the coal and partly
in the roof slate, and laminations of the roof slate may pass through
some of the concretions.

Another evidence that the concretions have formed early in the
history of the coal seam, in addition to the preservation of the plant
structures, is that the vegetal matter has been squeezed down around
the balls while they have been scarcely compressed. They must have
been in existence before the compression of the vegetal matter occurred,
and the presence of slickensides shows that the coal and accompanying
rocks were squeezed around them. It is only reasonable to suppose
that these concretions were formed on the bottom of the marsh in
which the vegetal matter grew and that they may have originated
by the action of algae or other low forms of plants causing precipitation
of calcium carbonate, as many calcareous concretions originate at the
present day. As they grew, fragments of plants came in contact with
them and were enclosed. In the case of the iron-carbonate concre-

1 Jeffrey, E. C., Petrified coals and their bearing on the problem of the origin of coals.
Proc. Nat. Acad. Sci., Vol. 3, pp. 206-211, 1917.

234

STRUCTURAL FEATURES OF COAL SEAMS

tions it is possible that they resulted from the reaction of ferrous sul-
phate and calcium carbonate in the presence of carbon dioxide. If
the supply of carbon dioxide were insufficient, limonite would have

FIG. 74. Coal stringer, Brilliant Coal and Coke Co. Horn Mine Duquoin, 111.
(From the Bull. 111. Geol. Survey, University of 111. and U. S. Bur. of Mines.)

formed instead of siderite and in the presence .of hydrogen sulphide
iron pyrite would have been precipitated to form sulphur balls. As
to the agent causing precipitation of the iron compounds the iron

1 1

, i

1 1 1 1 1

1 1

''. ; v. '. : ' ''...'..:''..'.-.' /. :.':.'.''''.'..'.'. ' -'..'-'"-'.' ''.'

1 1 1 1

1 1

, /

^^^^v^.^^ : :^ : .VvV:^VV^^V;V-vV^X^:V:^^'^'v;:^\V: : :^y.'. /.''.'.'.

1 1 1 1 1

1 I

1 1

i /

'' :''..':'.:':.''.' .^': :: :::'.'-'-'-'-'-:'--'.--::-'.-'.-'-'. - y-'.--':- ''.'.-:

1 1 1 1

1 f

.;::::v?H

fff-^-y-

vU-::HU'--:-}:l : .Ov/;^nastQiiB:^-vv;^::-:;i-:-;:i:v

ll.imhsvni'ie 1

1 1

1 1 1 1

).imps

ni e 1

**/.' ' ' '."' Y"'\ ' *

1 1 1 1 I

i ' r

1 ' 1 '

T ' 1 '

-V-r
jjj.

piiiiiiii^i*

, 1 , 1 , 1 , 1 ,

I _

SCALE IN FEET
(T~l 2 5 4 5

FIG. 75. Roll in roof, Madison Coal Corporation Mine No. 6, Divernon, 111. (From
Bull. 111. Geol. Survey, University of 111. and U. S. Bur. of Mines.)

bacteria may have played a part or the balls may be replacements of
calcareous nodules.

In size these balls may vary from minute nodules, less than an inch
in diameter, to bodies several feet in diameter. One ball about 4

"NIGGERHEAD" COAL 235

feet in diameter and estimated to be of about 2 tons weight was found
in a mine at Shore, England, and it almost completely cut out the coal
seam. The balls are usually roughly spherical and some large ones
are made up of several smaller concretionary centers cemented to-
gether by carbonate and carbonaceous matter.

The analysis of the calcareous nodules according to S topes and
Watson showed calcium carbonate (CaC0 3 ) as high as 91.09 and as
low as 49.35 per cent, and magnesium carbonate (MgCO 3 ) reaching
42.82 per cent, thus indicating that some of them consist almost en-
tirely of dolomite. Iron pyrite was found as high as 3.27 per cent, and
other constituents, as ferrous carbonate, ferric oxide, manganese
carbonate and calcium phosphate occurred in small amounts.

The studies of Zalessky 1 in the Donetz Basin of Russia showed that
the calcareous balls occurred there under conditions almost identical
with those described for England and northern France. The coal
seam and the shales carrying abundant concretions lay between two
limestones and the same types of plant remains were preserved in
much the same way.

" Niggerhead " coal. In the Walsenburg district of Colorado and
in the coal fields of Washington State and Alaska certain seams of coal
have been intruded with igneous rocks and a great deal of natural
coke occurs. In some of these seams most of the coal is made up of
roughly spherical masses called " niggerheads," varying from an inch
or less to a foot or more in diameter. They resemble somewhat the
form taken by diabase or other basic rocks on disintegrating by
spheroidal weathering. The laminations in the coal are still distinct
in most of the balls, and in many of them portions of flat sides indicate
the original joint cracks, but the corners are rounded off and some of
the balls are almost spheres, (Fig. 77).

It might be thought that these bodies owe their form to a sort of
concretionary development as a result of silicification or other form
of mineralization of the coal when it was intruded by the igneous
rock, but the following analyses show that it is not high in ash and it
is considered a very good quality of coal in the Rocky Mountain
fields.

1 Zalessky, M. D., On the discovery of the calcareous concretions known as coal balls
in one of the coal seams of the Carboniferous strata of the Donetz Basin. Bull, de 1'ac-
ademie Imperiale des Sciences de St. Petersburg, VI Series, pp. 477-480, 1910.

236 STRUCTURAL FEATURES OF COAL SEAMS

The subspherical form is apparently due to the coal being heated
to a high temperature with the driving off of certain volatile matter.

FIG. 76. A sharp syncline near Hazelton, Pa., from which the anthracite has been
removed by open-cut mining. (Photo by E. S. Moore.)

FIG. 77. "Niggerhead" coal from Colorado.

It then contracted so that it scales off concentrically in the same
manner as any other rock which has been heated and allowed to cool.

"NIGGERHEAD" COAL 237

ANALYSES OF NIGGERHEAD COAL FROM COLORADO 1

Fixed. carbon

Per cent

"?3 OQ

Per cent

ff 2O

Per cent

ri e;i

Per cent

rA gl

Volatile matter . .

27 CQ

57 78

31 QO

?r Si

M^oisture

2 06

2 22

** *

2 D3

Sulphur

Q06

.714

714.

742

Ash . .

7 3^

4.80

q 8s

6 7C

Sp. gr. ... . .

1.308

i . 300

I 324

I 312

B.t.u. (dry).

13,631

13,746

12,080

13,12^

1 Analyses furnished through kindness of D. A. Stout. From Huerfano County,
Colorado. I, Cameron seam, II and III, Walsen seam and IV, Robinson seam.

There is also evidence in the smooth surfaces of the balls that consid-
erable movement has occurred between them and the adjacent coal.
This may have resulted from the great pressure exerted when the
intrusion entered the coal seam and adjacent rocks and it probably
aided in forming the rounded bodies. The spherical structure was
apparently formed after the coal was jointed into blocks since rem-
nants of the joint planes may still be seen in most of the balls. These
joint fractures in all probability aided in the distribution of the heat
from the igneous rocks and in the irregular cooling of the coal when the
volcanic activity had subsided

The only other specimen of coal resembling these " niggerheads "
from Colorado, which the writer has seen was found in a seam in the
Newcastle district of Australia. That seam had also been intruded
by igneous rock and a spherical mass found gave unmistakable evi-
dence of having suffered from great pressure and some shearing. It
was thought at the time to have been the result of pressure squeezing
the more plastic coal around harder lumps of the vegetal matter in
the seam, but it is probable that the heating of the coal may also have
had an influence in producing the concretion-like body. A few speci-
mens of these bodies have been reported from the Anthracite field
of Pennsylvania apparently formed by pressure on the coal.

The nature of the origin of these peculiar bodies does not seem to be
fully understood by mining men and more extensive observations re-
garding them are needed.

CHAPTER IX

PROSPECTING FOR COAL AND THE VALUATION
OF COAL LANDS

Prospecting

Prospecting for coal may be considered as two operations. One
of these is the search for coal in regions where it has not already been
found and the other the testing of geological formations already
known to contain at least some coal.

SEARCHING FOR COAL IN NEW FIELDS

Laws governing operations. According to the laws of the United
States, coal lands are classed as Mineral Lands and unoccupied coal
lands may be obtained through the government departments. The
legal conditions controlling the purchase of lands already occupied are
quite different. The Land Office Regulations relating to entry on
vacant coal lands in the Public Land States and Territories and the
district of Alaska are as given below, (Sees. 2347 and 2348). These
were issued April 12, 1907 and they abrogate all previous rules and
regulations relating to coal lands, 1 (Sec. 2347).

Every person above the age of twenty-one years who is a citizen
of the United States, or who has declared his intention to become such,
or any association of persons severally qualified as above, shall, upon
application to the register of the proper land office, have the right to
enter by legal subdivisions, any quantity of vacant coal lands of the
United States not otherwise appropriated or reserved by competent
authority, not exceeding 160 acres to such individual person, or 320
acres to such association, upon payment to the receiver of not less than
ten dollars per acre for such lands, where the same shall be situated
more than 15 miles from any completed railroad (one constructed,
equipped, and operating on date of entry), and not less than twenty

1 Charles Shamel, Mining, mineral, and geological Law. Hill Pub. Co., 1907.

238

LAWS GOVERNING OPERATIONS 239

dollars per acre for such lands as shall be within 15 miles of such road.
This statute was authorized March 3, 1873, and is still applicable.
The lands which may be entered must be surveyed and legally sub-
divided, they must contain workable coal deposits, but they must not
contain valuable deposits of gold, silver, or copper.

Coal lands may also be entered according to the following statute
(Sec. 2348) on the basis of a preference right to purchase: Any
person or association of persons severally qualified (as provided in
Sec. 2347), who have opened and improved, or shall hereafter open
and improve, any coal mine or mines upon the public lands and shall
be in actual possession of the same, shall be entitled to a preference
right of entry under the preceding section (Sec. 2347) of the mines
so opened and improved : Provided, that when any association of not
less than four persons severally qualified as above provided shall have
expended not less than five thousand dollars in working and im-
proving any such mine or mines, such association may enter not ex-
ceeding 640 acres, including such mining improvements. To preserve
a preference right the person or association must present to the register
of the proper land district, within sixty days from the date of actual
possession and commencement of improvements a declaratory state-
ment therefor, in all cases when the township plot has been filed.

An individual or the several individuals of an association are en-
titled to but a single entry on coal lands. No one can operate or
work a coal mine for profit upon the public lands without having
made the proper entry.

Those desiring information regarding public coal lands should
apply to the register of a land district, who is furnished from time to
time with schedules and maps. These maps show three types of
lands: (i) Those lands known to lie outside of ascertained coal areas
and open to entry under the general land laws. (2) Those lands
known to contain workable deposits of coal, whereon prices will be
fixed upon information derived from field examination. (3) Those
lands containing coal of such character as may from their location
with reference to transportation lines, be sold at the minimum price
fixed by statute. The lands of the first and third types are entered
at minimum prices as stated above and those of the second type at
prices fixed in the schedules.

240 PROSPECTING AND VALUATION OF COAL LANDS

Entry on coal lands in Alaska: To make entry on unreserved
coal lands in Alaska 1 the same individual and personal qualifications
are necessary as in the United States but entry may be made on un-
surveyed coal lands. In unsurveyed tracts the lands upon which a
mine or mines are situated must be located in rectangular tracts of
40, 80, or 1 60 acres with north and south boundary lines run accord-
ing to the true meridian and marked by permanent monuments.
All locators shall within one year of making a location file a notice
with the register of the land district.

To obtain a patent an application for such must be filed with the
register and receiver of the land district within three years. A patent
gives control of the land to the patentee and his heirs.

The regulations governing the control of coal deposits in lands
other than the Public Lands of the United States vary with different
states. In many states the person holding land in fee also holds the
minerals lying beneath the surface unless they have been expressly
reserved in the deed. In others, such as Wyoming and Colorado,
the coal land is leased only on a royalty basis.

The recent leasing law for coal lands: On February 25, 1920, the
President of the United States signed an act known as an " Act to
promote the mining of coal, phosphate, oil, oil shale, gas and sodium
on the public domain." This bill places the development of these
lands, not including those of Alaska, under the control of the Secretary
of the Interior and it throws open millions of acres of coal and oil
lands in the West for leasing purposes. The law refers to lands
classified or unclassified but it does not include : (a) Lands in .National
parks; (b) Lands controlled by the Appalachian Forest Reserve Act;
(c) Lands in military or naval reservations; (d) Indian reservations;
(e) Ceded or restored Indian lands the proceeds of which are credited
to the Indians.

According to this act coal lands may be leased to citizens, asso-
ciations of citizens, corporations, and municipalities in tracts of 40
acres or multiples thereof up to 2560 acres by one applicant. The
tracts are to be contiguous if possible for them to be so. Railroads
may work for their own use for railroad purposes only one grant for

1 Regulations governing Coal Land Leases in the Territory of Alaska. Dept. of the
Interior, Washington, May 18, 1916.

LAWS GOVERNING OPERATIONS 241

each 200 miles of road. There is to be paid to the Government a
royalty on coal leases of not less than 5 cents a ton (2000 Ibs.) and a
yearly rental of not less than 25 cents an acre for the first year, not
less than 50 cents an acre for the second to the fifth year inclusive,
and not less than $1.00 an acre for the remainder of the term of the
lease. Leases are for indeterminate periods not to exceed twenty
years but renewable to a like extent. In an emergency individuals or
associations may be allowed to mine coal for their own domestic use
without payment of rent or royalty. This privilege is restricted to an
area of 40 acres and a license of two years duration. Municipalities
may lease coal lands for their own use without the payment of rent
or royalty under the following special conditions: The coal must
be used for domestic purposes only, which means household purposes;
a municipality of less than 100,000 population is limited to an area
not exceeding 320 acres, one of 100,000 to 150,000 population to an
area not exceeding 1280 acres and one of a population of over 150,000
is limited to an area not exceeding 2560 acres. The special lease
granting this privilege is limited to four years.

No person, association or corporation, except as provided, shall
have more than one coal, phosphate or sodium lease during the life
of such lease in any one state. " No person or corporation shall take
or hold any interest or interests as a member of an association or
associations or as a stockholder of a corporation or corporations hold-
ing a lease under the provisions of this bill which together with the
area embraced in any direct holding of a lease under this Act or which
together with any other interest or interests as a member of an associa-
tion or associations or as a stockholder of a corporation or corporations
holding a lease under the provisions hereof, for any kind of mineral
leased hereunder, exceeds in the aggregate an amount equivalent to the
maximum number of acres of the respective kinds of minerals allowed
to any one lessee under this Act. Any interests held in violation of
this Act are forfeited to the United States."

Permits, known as coal prospecting permits may be granted, which
gives the holder the exclusive right to prospect unclaimed and un-
developed lands where exploratory work is necessary to determine
the existence or workability of coal deposits. These permits cover
a maximum area of 2560 acres and they are good for two years.

,.-

242 PROSPECTING AND VALUATION OF COAL LANDS

CRITERIA FOR LOCATING NEW SEAMS OR KNOWN SEAMS
IN NEW AREAS

In looking for new seams of coal there are certain conditions which
should govern the prospector's operations. A seam may outcrop
at the surface but if the adjacent rocks have suffered much disin-
tegration very little definite evidence of the coal may be found with-
out excavating. There may often be found a black band, or area,
known as the " smut " or " blossom " which indicates the position
of the seam. In some cases the presence of a seam which is covered
with clay or sand wash may only be inferred by finding minute frag-
ments of the coal mixed with the sediment carried down grade by
water or transported in a certain direction by a glacier. Outcrops
are most frequently found in gullies and ravines and quite frequently
seepages or springs of water in the bank indicate the position of seams
of coal.

In prospecting it should be observed that coal is only found in
stratified rocks, and it is absolutely useless to search for it in those
of igneous origin. Further, of the stratified rocks, there are usually
certain types which carry the coal. These are shales, or slates de-
rived from the shales, and sandstones. Black shales are the most
favorable. Although coal has been found in limestones, it is very
rarely indeed that it is found in a limestone formation in which there
is not also considerable shale or sandstone, and there is no chance
of finding it in quantities in distinct limestone formations. Regard-
ing sandstones and conglomerates, the latter rarely carry coal except
along shaly and sandy bands. Clean sandstones are poor coal-
bearers as most of the coal in sandy rocks is found in impure sand-
stone containing clay or in feldspathic sandstones known as arkoses.

Although shales and impure sandstones are favorable rocks for the
occurrence of coal not all of them carry it. In America no coal has
been found in rocks older than those of the Mississippian, or Lower
Carboniferous series, but in Europe a little has been found in rocks
as old as the Devonian. Carbonaceous shales may be found as low as
the Archean rocks, but the geological and botanical conditions had
not become favorable for the formation of coal before the periods
mentioned above. There are many examples of people spending
large sums of money in drilling in these older formations, as for ex-

CRITERIA FOR LOCATING NEW SEAMS 243

ample, in the Ordovician black shales, where there is no possibility
of finding coal. There is good evidence to show that the great groups
of land plants which gave rise to the coal had not developed before
the Devonian period, and in America as well as in some of the other
continents the sea covered so much of the continent that there was
little opportunity for coal to form in the Devonian.

The coal-bearing formations are found principally in the Carbon-
iferous, Cretaceous, and Tertiary systems. There is a little coal in
the Jurassic in Alaska, and outside of America the Jurassic and Tri-
assic coals are important. In dividing these systems of rocks into
smaller divisions so that certain seams of coal may be located or a
seam may be traced from one basin to another the different plant
fossils may be used to correlate beds, and animal fossils in the ad-
jacent rocks often serve to identify the seams. Thiessen claims to
have discovered from his microscopic studies that the plant spores
found in any coal seam have characters distinct from those of spores
in other seams, and may be used as a determinative factor in recog-
nizing the seam in various localities. This new evidence of the dif-
ference in the spores from different seams is likely to be of considerable
practical value in the future in correlating seams.

In addition to the fossils there are often other features which
locally distinguish one seam from another, such as the presence of
" sulphur balls " or other concretions in some seams and their ab-
sence in others, the fracture of the coal, the presence of streaks of
cannel or mineral charcoal, the nature of the adjacent rocks and
similar features. The adjacent rock may be a fire clay, a calcareous
rock or some distinctive sandstone which can be recognized wherever
met.

Testing coal-bearing formations to determine the extent of the
seams. A coal seam may vary greatly in thickness within very
short distances or it may, like the Pittsburgh seam of the Appalachian
province, extend with a fairly uniform thickness over several thous-
and square miles. Shallow seams may be tested with tunnels, pits,
or shafts, but where they lie much below the surface prospecting is
usually done with a core drill. The diamond drill is most commonly
used, although a rotary calyx drill has also been employed. The
advantage in using drills of this type is in the core which is obtained.

As few coal seams lie horizontally the length of the section of coal

244 PROSPECTING AND VALUATION OF COAL LANDS

in the drill core from any seam will depend upon the angle at which
the hole perforates the seam and will vary inversely as the acute angle
for a vertical hole. If the hole be vertical, the angle will be found by
subtracting the angle of dip of the bed from 90, that is, the angle
will be the complement of the angle of dip. In case the hole is not
vertical but is still in a plane normal to the strike, the angle which it
makes with the seam can be found by subtracting the angle of dip
from 90 and then adding the angle the hole makes with the vertical,
if it be inclined in the opposite direction to the seam, or subtracting
it, if it be inclined in the same direction. These figures may be easily
obtained by use of a clinometer.

If the hole is driven so that it departs from the vertical in a plane
which is parallel to the strike and therefore normal to the dip, the
difference between the true thickness of the seam and the thickness
shown in the core will increase as the angle which the hole makes with
the vertical increases.

In the case of holes drilled at an angle to the vertical and lying in
any other plane than the plane parallel to the direction of strike of
the seam or in the plane normal to the strike, as
mentioned above, the conditions become quite com-
plicated and must be worked out for each individual
case.

In all the cases mentioned above, the true thickness
of the seam may be determined from the thickness
of coal in the core by a solution of the triangles in-
] D volved, but the simplest method and one sufficiently
accurate for all practical purposes is to solve the
]B problem graphically. This is done as follows: In
FIG. 78. Graphic Figure 78 let A B be a drill core containing a band
method of deter- o f coa i CD. Carefully project the coal seam, keeping
mining the thick- ^ inclination, and draw a line from A per-

ness of a coal seam

from the drill core, pendicular to the projected seam. The distance EF
will bear the same relation to the distance CD
(which is already known) that the true thickness of the seam does
to the thickness of the coal in the core since they are drawn to the
same scale. If CD be 10 feet and EF scales half as much as CD
the true thickness of the seam will therefore be 5 feet.

DETERMINATION OF THICKNESS OF COAL FORMATIONS 245

Determination of thickness of ccal formations. There are several
means of determining the thickness of an outcropping coal seam or
of a formation containing one or more seams, without the use of the
drill. The method employed depends upon the circumstances, (i)
If the beds lie flat and are exposed in a cliff (a) the vertical height of
the cliff will be the thickness. (2) If the beds dip there may be sev-
eral different conditions: the surface may be level where the for-
mation outcrops (b) ; the rocks may outcrop in a slope, which is inclined
in a direction opposite to the direction of the dip of the strata (c) ;
the rocks may outcrop in a slope which is inclined in the same direction
as the dip of the strata, (d) (Fig. 79). The thickness of the formation

FIG. 79. Determination of the thickness of a formation under varying conditions.

is found by solving the triangles in the three cases, (b), (c), and (d)
as follows: (b) Since the angle of dip ACB and the distance CA may
be measured, the distance AB is easily found from the formula.

Sin ACB = , or AB = CA Sin ACB, (c) AB = CA Sin (ACD -f

O^T.

DCB). The slope distance and angle of dip are measured and the
angle of slope ACD may either be measured or found from its sine,
computed from the length of the slope and the difference in elevation.
(d) AB = CA sin (DCB - DC A).

As the angle of dip increases the horizontal distances normal to the
strike approach more nearly the thickness of the formation until the
dip becomes 90, or vertical, and the two are then equal.

Graphic method: The thickness of a series may be very conveniently
and rapidly determined by the graphic method when the angle of dip
and the horizontal distance across the outcrop are known, (Fig. 80).
In this diagram the numbers on the left hand side of the diagram repre-
sent various dip angles and each vertical space corresponds to any
chosen unit of measurement. To determine the thickness find the
number corresponding to the number of degrees in the dip angle and
follow the horizontal line to the right for as many units as there are

246

PROSPECTING AND VALUATION OF COAL LANDS

in the distance across the outcrop. Then follow the curved line (or
an imaginary curved line between two of the curved lines if the point
falls between two lines) to the top of the figure and count the number
of units between the point reached and the left margin. The vertical
spaces may each be taken as equal to 5, 10, 20, 100, 1000, or any other
number of feet, the same scale being used in all parts of the diagram

FIG. 80. Diagram employed in the graphic determination of the thickness of geological
formations. (After Hayes.)

in any one calculation. To illustrate its use: Let a formation out-
cropping on a level surface dip 30 and the distance across its outcrop
normal to the strike be 1000 feet. Its thickness is found by following
the horizontal line from 30 to the right and if each vertical space be
considered equal to 100 feet, the point corresponding to 1000 feet will
fall on the fifth curved line. If this line be followed to the top of the
diagram and the same scale be used, it will be found that the distance
to the left margin is 500 feet. Instead of considering each space

DETERMINATION OF DEPTH OF COAL SEAM 247

equivalent to 100 feet another scale might have been used, for example
200 feet or 50 feet per space. It is best in all cases to use as small a
number of feet to a space as the diagram will permit in order to
minimize the error in computing the thickness. In this connection
it is sometimes wise to use a certain fraction of the distance across the
outcrop to obtain the thickness of that fraction of the formation, and
then to find the total thickness from this fraction. For example the
total distance across the outcrop of the formation is 2000 feet. In
order to use a large scale on the diagram find the thickness corre-
sponding to a distance of 200 feet and multiply this by 10, to find the
thickness for the whole formation.

In addition to the methods suggested above, the thickness of a
formation may be determined graphically by simply drawing to scale
diagrams like those in Figure 79, and scaling off the distance repre-
senting the thickness. If this is done carefully and on a fairly large
scale the results will be satisfactory for most purposes since in most
cases thicknesses and dips are subject to considerable variation within
short distances.

Determination of the depth of a coal seam at different points. -
If an outcropping seam lies flat its depth below the surface at any
point can readily be found from the topographic map. On many
geological maps structural contour lines are drawn on one important
seam in a coal-bearing formation and all points on any one of these
lines have the same elevation above sea level. These contours bring
out the subterranean topography and the structural features of the
seam and when they are placed on a topographic map the depth of
the seam at any point is quickly found by taking the difference be-
tween the elevation of the surface at that point as shown on the top-
ographic map and the contour line on the seam lying beneath this
point, (Fig. 81).

When an outcropping seam dips it may be desired to find its depth
at certain points at various distances, and in various directions from
some point on the outcrop. For convenience in discussion, the
depth of a seam in three directions from a point on the outcrop and
at varying distances from that point will be considered. The con-
ditions are illustrated by Fig. 82. Let A BCD represent a section
of a seam outcropping along AB. The direction of strike is parallel
to AB and the direction of dip normal to AB and parallel to PM.

248

PROSPECTING AND VALUATION OF COAL LANDS

100

FIG. 81. Relation between surface contours and structural contours drawn on the
surface of a coal seam underground. The former are the light lines and the latter
the heavy ones.

/ M

/'I,' JM X

j / \ 1

'' i

\ (

/ \

, \

;X \

;

/ \

, \

FIG. 82. Diagram illustrating the determination of the depth of a coal seam at
varying distances and in different directions from a point on the outcrop.

DETERMINATION OF DEPTH OF COAL SEAM

249

(i) In the first case consider the depth of the seam below various
points L, O, and M, along a line parallel to the dip. The angle of
dip, MPN and the distances PL, PO, or PM being measured, the
depth is found from the tangent of the angle of dip. It is seen that
the depth at any point will be directly proportional to the distance
from the point P, and the following table shows the depth of a seam
at points 10 feet from a point on the outcrop when measured on a
horizontal surface, supposing the seam dips at various angles from 5
to 85. At 90 the bed is vertical. To find the depth of the seam
beneath any other point along this line multiply the number given in
the table by the distance in feet and divide the result by 10.

TABLE SHOWING THE DEPTH OF A COAL SEAM AT VARIOUS

DISTANCES IN DIRECTION OF DIP FROM THE OUTCROP,

FOR DIFFERENT ANGLES OF DIP

Angle of dip

10 feet from outcrop

Angle of dip

10 feet from outcrop

.8749 feet

11.918 feet

I-7633

14.281

2.6795

17.321

3.6397

21-445

4-6631

27-475

5-7735

37-321

7.0021

56.713

8.3910

114.300

IO.OOOO

(2) In the second case consider the depth at various points along
a line 45 from the direction of dip. Or in the diagram (Fig. 82)
let the direction of the dip be south, the strike east and west, and the
direction (PH) under consideration, southeast. On this line, PH
the depth at any points such as E, F, and H, will be found by first
measuring the distance PE, PF, or PH, then drawing a line from
this point normal to the line PM meeting PM at the point K. The
triangle PFK thus formed is solved, PK is found and the problem
then becomes the same as that described above for the first case con-
sidered. The following table shows the depth of a seam at points
10 feet from a point on the outcrop, measured for various dips of
5-85 in a direction 45 from the direction of dip.

To obtain the figures for any other point, multiply by the distance
in feet and divide by 10.

2 5

PROSPECTING AND VALUATION OF COAL LANDS

TABLE SHOWING DEPTH OF A SEAM AT POINTS ALONG A

LINE 45 FROM DIRECTION OF DIP FOR VARIOUS

ANGLES OF DIP

Angle of dip

10 feet from outcrop

Angle of dip

10 feet from outcrop

.61855 feet

8.42602 feet

i . 24665

10.09666

1.89440

12.24594

2.57326

15.16161

3-29681

19.42482

4.08176

26.38594

4.95048

40.09609

5.93243

80.81010

7 .07110

The formula for determining the depth D at a point C feet from the
outcrop and in a direction at A to the direction oi dip, if the angle
of dip be B, is

D = Tan. B x C cos A.

An instrument known as Brunton's slope chart is a convenient ap-
paratus for determining the apparent dip of the bed at any angle
of divergence from the true dip. It is for the purpose of mechanic-
ally solving the formula Tan C = Sin A Tan B, where A is the angle
of divergence from the true dip, B the true dip, and C the apparent
dip. Thus, after the angle C has been found, the depth at any point
is found just as in the case where the measurement is taken along the
true dip by finding the tangent of C and using the table given for the
first case.

(3) In the third case it should be observed that any point along the
line of strike of a coal seam will be at the same depth as every other
point on that line whether the seam be considered at the surface or
at the bottom of a mine shaft. This is evident since the strike is the
line along which the seam intersects a horizontal plane.

The Valuation of Coal Lands

Factors governing the value. The chief factors which influence
the value of coal lands are : (a) the proximity of the coal to an impor-
tant market center; (b) the transportation facilities; (c) the abundance
or scarcity of coal in the district; (d) the nature of the coal; (e) the
depth at which it occurs; (/) the thickness of the seam; and (g) the

DEPTH OF COAL MINE SHAFTS IN UNITED STATES 251

other geological conditions which affect mining operations, such as
folded or faulted strata, abundance of water and the character of
the floor and roof of the seam. -The nearness of coal deposits to a
good market may be offset by labor difficulties and poor quality of the
coal or the difficulty of mining it, while the handicap of being a con-
siderable distance from the market may be overcome by good trans-
portation facilities, especially by water, and the favorable condition
of most of the other factors mentioned. If there be little fuel in the
vicinity of a large city the lower grades of coal, such as lignite, may
bring a good price whereas they would scarcely be used if there were
plenty of good bituminous coal or anthracite in the region. Good
gas coal is in demand, especially around cities, and high-grade coking
coal is much sought after for metallurgical purposes. If it occurs in
large amounts, industrial centers may grow up in areas where it is
found.

THE MAXIMUM DEPTH OF COAL MINES

The depth of coal mine shafts in the United States. In the

United States it is customary to regard any coal lying below 3000
feet as negligible in estimating the value of the land, because industrial
conditions make it impossible at present to mine the coal profitably
at a greater depth. It is the consensus of opinion, however, that the
time is not far distant when the maximum depth for profitable mining
will be extended to at least 4000 feet, as this depth is almost attained
in Belgium at the present time, and in England for almost half a century
all seams less than 4000 feet deep have been figured in the reserves.
There are no mechanical impediments to mining at that depth or
even at a much greater depth; but the abundance of coal, the high
cost of labor and the low price which usually prevails in the United
States when compared with prices in those countries where deep min-
ing is carried on make it impossible to mine coal profitably at these
great depths in this country.

The maximum depths at which coal is mined at the present time
in the various fields of this country are approximately as follows: 1
The deepest mining is in the anthracite region of Pennsylvania, and
it reaches about 2200 feet although the deepest shaft is only 1850 feet.

1 Fisher, C. A., Depth and minimum thickness of coal beds as limiting factors in valu-
ation of coal lands. U. S. Geol. Survey, Bull. 424, p. 48, 1910.

252 PROSPECTING AND VALUATION OF COAL LANDS

This depth does not indicate the maximum depth of the coal in the
anthracite region as the depth of a few of the basins has not yet been
determined and from every indication it is very great. In the not
far distant future it is probable that coal will be mined from the
Southern Field at a depth of at least 3500 feet. In the Schuylkill
section the coal probably reaches 4500 feet or more in depth.

In the bituminous fields of the Appalachian province the coal does
not lie at great depths in many places, the deepest so far known being
in Alabama where some of it exceeds 3000 feet. The deepest shafts
are not over 1000 feet in the states of Pennsylvania, Ohio, West
Virginia, eastern Kentucky, Tennessee, and Alabama, and there are
large areas where all shafts are less than 200 feet in depth.

In the Eastern Interior field, including Illinois, Indiana, and western
Kentucky, the greatest depth reached is at a mine in Illinois, which
is slightly over 1000 feet, but most of the coal in these states is com-
paratively shallow. In Michigan the seams lie very close to the sur-
face and the shafts are seldom, if ever, more than 200 feet deep.

In the Western Interior field the depth reached in Iowa, Missouri,
and northeastern Kansas scarcely exceeds 300 feet, while in eastern
Kansas, Oklahoma, and western Arkansas the depth is considerably
greater. A test shaft 1 1 70 feet deep was sunk near Atchison, Kansas,
but it has not been regularly operated. With the exception of this
one the deepest shaft is about 800 feet and is found in the McAlester
district of Oklahoma. In Arkansas the deepest shaft is about 500
feet and in Texas the shafts are comparatively shallow.

In the northern Great Plains province mining has not been carried
beyond about 500 feet. A shaft 480 feet deep has been reported
from the Judith Basin region and there are some less than 400 feet
near Sheridan, in the Fort Union region. In the Black Hills region
the maximum depth is not over 400 feet and in the Assinniboine
region of northern Montana not over 300 feet.

In the Rocky Mountain province, owing to more intense folding
and faulting, the depth of the mines is considerably greater than in
the Great Plains or the Interior province. In Wyoming, at Rock
Springs, there is a shaft about 2000 feet deep and in the Hams Fork
region there is one which is reported to be over 1600 feet. At Coke-
dale, Montana, a mine was worked at a depth of 1300 feet and near
Carbondale, Colorado, the Spring Gulch mine is down about 1500

THE MINIMUM THICKNESS OF COAL SEAMS MINED 253

feet. In southern Colorado and northern New Mexico there are some
mines working at a depth of over noo feet, and in the vicinity of
Glenwood Springs, and at Canon City, Colorado, shafts are about
1000 feet deep. Elsewhere in the Rocky Mountain province the
mines are generally less than 600 feet deep. In the Pacific Coast
province the deepest mines are found in Washington. The Roslyn
mine is said to be over 700 feet deep. In the Coos Bay field of Oregon
the coals lie under 500 feet of strata and in central California the depth
is about 300 feet.

The maximum depth of coal mines in foreign countries. The
deepest shaft in the world is in Belgium and the latest figures avail-
able give its depth as 3937 feet. Other mines in the Mons district
of that country run from 2500 to over 3000 feet. The average through-
out Belgium is placed at 1444 feet by E. Loze.

In England the Rams mine at Manchester is not far short of the
depth of the Belgian shaft, being over 3480 feet; a seam 2 to 6 feet
in thickness is worked at this mine. In the same district there are
two other mines each over 3300 feet in depth, but these are not classed
as shafts. A number of mines in other fields run from 2000 feet to
over 3000 feet. In South Wales the Ocean Collieries reach 2700 feet. 1
In Scotland the deepest workings are near Edinburgh and they are
down to 2700 feet. The deepest shaft in Great Britain is said to be
2820 feet, but some of the collieries mentioned above are considerably
deeper than this shaft. In France some mines reach 3000 feet and
in Germany mining has been carried to over 3100 feet. In the Rhen-
ish- Westphalian district the average depth of the mines is said to be
about 1 700 feet.

Australia has a shaft 2937 feet deep near Sydney Harbor, New
South Wales. This shaft was sunk to a 3-foot bed of coal which out-
crops at Newcastle and dips southward towards Sydney.

THE MINIMUM THICKNESS OF COAL SEAMS MINED

There are several factors which govern the minimum thickness at
which coal seams may be worked. The most important of these
factors are: the market for, and the character of, the coal; the
nature of the enclosing rocks; the association of a thin seam with
other seams; the depth of the seam; and the training of the miners.
1 Report of the Royal Commission on Coal Supplies, 1871 and 1901-1905.

254

PROSPECTING AND VALUATION OF COAL LANDS

So far, much thinner beds are worked in some foreign countries than
in the United States. The cost of mining thin seams usually increases
rapidly as most miners demand a bonus or refuse to work the seam if
it be less than a certain thickness. A mine manager in New Zealand
stated that the labor conditions there prohibit the working of any
seam less than 4 feet thick and the contract price for mining at one
mine visited by the writer was 2 shillings 8 pence for a seam 4 feet
to 4 feet 6 inches thick down to 2 shillings 4 pence for a seam 5 feet
thick or over, showing a decrease in cost of mining of 4 pence per ton
for an increase in thickness of 6 inches or more.

Thin seams mined in the United States. Owing to the high
quality of certain thin seams of coal or their chance location near a
large city or important industrial center, the working of them is not
confined to any particular part of the country. The following table
compiled from the work by Fisher 1 shows the thickness of the thinnest
seams reported as worked in the various states.

TABLE SHOWING THE THICKNESS OF THIN COAL SEAMS
WORKED IN VARIOUS STATES

State

Thickness of Seam

Alabama

22-24 inches.
14 inches. From a stripping.

18-42 inches. From a drift.
18-84 inches. From a drift.
20 inches. From a slope.
17 inches. From a drift.
22 inches.
14-18 inches. From a shaft 230 feet.
15-18 inches. From a shaft.
24 inches.
30 inches.
24 inches.
12 inches. From a shaft 44 feet.
12 inches. From a drift.
30 inches .
7-15 inches.
26 inches.
22 inches.

1 8 inches.
17-48 inches.
22 inches.
19 inches. From a shaft.
20-24 and 24-36 inches.
16 inches.

Arkansas

Colorado
Anthracite

Bituminous

Illinois

Indiana

Iowa

Kansas

Kentucky

Maryland

Michigan

Missouri

Montana

New Mexico

Ohio

Oklahoma

Pennsylvania
Anthracite field

Western Clearfi eld district . .
Tennessee

Texas

West Virginia

Wyoming . .

Op. cit., p. 69.

VALUE OF COAL LAND PER FOOT- ACRE 255

Many of the thin seams in this table are mined for local use and
nearly all of them are comparatively shallow. Some are from drifts
and some from strippings, so that on the whole their thickness is
rather below a good minimum for ordinary mining operations,
although the official regulations governing coal lands of the United
States place the minimum limit of thickness for a workable seam at
14 inches.

Thin seams mined in other countries. Some very thin seams of
coal of special quality have been worked in foreign countries. A
bed of cannel 8 inches thick has been mined in Lancashire, England,
and this probably represents the thinnest seam on record. Many
beds ranging from 10 inches to 20 inches and consisting of various
types of bituminous coal have been mined in different parts of England
and Wales, while in Scotland beds ranging from 15 inches upward
in thickness have been worked.

In Belgium several seams not more than n inches thick have been
worked, and other seams 13-15 inches thick are regularly mined where
the coal is of high grade.

ESTIMATION OF THE VALUE OF COAL LAND PER FOOT-ACRE

The price of coal at the mine and the cost of mining. The value
of an acre of coal land in the United States before the war varied all
the way from $10 to $2000. The latter figure is that stated by
Ashley 1 for some of the land in the Connellsville district of Pennsyl-
vania. There are, however, some areas which are held at a much
higher figure than this.

In attempting to arrive at the value of the coal in the ground the
price per ton at the mine and the possible fluctuations in price are
taken as a basis. The figures given below represent the price of
coal at the mine in various states for the years 1912, 1913, and 1914?
and they may be taken as an indication of the prevailing prices in
different parts of the country although it must be remembered that
the price varies with the demand, and the location will have a great
influence upon the local price. For example, small outputs of coal
have sold as high as $4.10 per ton at the mine in Idaho even in normal

1 Ashley, G. H., The valuation of public coal lands. U. S. Geol. Survey, Bull. 424,
1910.

2 Mineral Resources, U. S. Geol. Survey, 1914.

2 5 6

PROSPECTING AND VALUATION OF COAL LANDS

years, and recently during a period of scarcity reports have been re-
ceived of coal selling for $10.00 and $11.00 a ton at some mines in
Pennsylvania.

TABLE SHOWING THE AVERAGE PRICE
PER SHORT TON AT THE MINE

State

1912

1913

1914

Alabama $ .29

Arkansas .71

California a .33

Colorado .49

Georgia .49

Illinois .17

Indiana .14

Iowa .80

Kansas .62

Kentucky .02

Maryland .18

Michigan .99

Missouri .76

Montana .82

New Mexico .42

North Dakota .53

Ohio .07

Oklahoma .14

Oregon .60

Pennsylvania Bituminous .05

Anthracite .11

South Dakota

Tennessee .14

Texas .67

Utah .67

Virginia o . 96

Washington 2 .39

West Virginia o . 94

Wyoming i . 58

Average Bituminous 1.15

Average Anthracite of Pennsylvania 2.11

$1.31
1.76

3-54
52

14
.11

79
67
OS
-24
99
73
74
.46
52
.10
05
53
.11

13
.96
14
77
65
.01
38
.01
56
.18
2.13

1.72
62.85
.66
44

.12
.IO

79
.64
.02
.27
99
73
75
.61

2.78

1.07

2.07

.69

59
.01

2.20
0-99

i-55
1.17
2.07

a Includes Alaska.

b Includes Idaho and Nevada.

After a consideration of many fields Findlay 1 concludes that the
cost of mining bituminous coal, including operating and related ex-
penses amounts on the average to about 96 per cent of the sale price.
The average cost per short ton to the Pittsburgh Coal Company from
a large number of mines for five years was 89 cents and to the Mononga-
hela River Consolidated Coal and Coke Company for nine years,
91 cents.

1 J. R. Findlay, The cost of mining, Eng. and Min. Jour., Vol. 87, p. 948, 1909.

VALUE OF COAL LAND PER FOOT-ACRE

257

In Pennsylvania, the cost of mining anthracite is considerably
higher than that of mining bituminous coal. The following figures
show the cost per long ton to three large companies in 1905.*

The Delaware, Lacka wanna and Western $i . 80

The Delaware and Hudson 2 . 09

The Lehigh Coal and Navigation Company 2 . 02

Between the years 1902 and 1908 the costs to the Philadelphia and
Reading Coal and Iron Company varied from $i .85 to $2 .00 per short ton.

The reports published by the committee of the Federal Trade
Commission 2 show the following figures for the cost of producing coal
in the several states mentioned, during recent years.
PENNSYLVANIA ANTHRACITE; AVERAGE COST PER GROSS TON

Labor

Supplies

General
Expenses

Total Cost
f.o.b. mine

1913-1918, inclusive

$1.58-3.31

$0.29-0.80

$0.33-0.61

$2.59-5.11

AVERAGE COST PER NET TON OF BITUMINOUS COAL.

Labor

Supplies

Total cost f.o.b. mine

Margin realized

Pennsylvania
1916 $0.82
1917-18 $0.88-1.38

1916 $0.92
1917-18 $1.12-1.73
Illinois, 5 districts.
1916 $0.74-1.48
i 917-1 8 $0.83-2.26
Ohio, 8 districts.
1916 $o 781 19

S. W. field.

$0.12

$0.17-0.27
Central field

$0.10

$0.15-0.31

$0.05-0.16
$0.07-0.32

$1.19
$1.35-$!. 94

$1.32
$1.62-2.38

$0.94-1.84
$1.05-2.85

$1 OO I 4.4

$0.17
$0.55-1.40

$0.08
$0.64-1.10

$0.03-0.12

$O . 2O-O . 80

IQI7 $O Q8 I 6^

$1 1<\ 2 21

1918 $1 252 24

$1 732 Q6

$0.54-1.03

Indiana, 2 districts.
1916 $o. 871 .52

$1 . OQ I . QQ

1917 $1.081.73

$i .372 . 16

1 .,

1918 $i .422 . 25

$i . 8^2 . 77

} $0.45-0. 51

Michigan.
1916 $1.58

$2.08

1917 $1.95

$2 -55

1 *, ..

1918 $2 52

$3 38

}$o.65

Alabama, 3 districts.
1918 $i 532 oo

$2 17-2 ^8

Tennessee, 3 districts.
1918 $i .302 . 14

Si .772 84

Kentucky, 4 districts.
1918 $1.25-1.61

$1 . 74-2 . 28

1 Chance, H. M., The cost of mining coal, Eng. and Min. Jour., Vol. 87, p. 1099, 1909.

2 Reports of the Federal Trade Commission on Coal, June 30, 1919.

258 PROSPECTING AND VALUATION OF COAL LANDS

The general expense increased gradually during the six years, but
the lowest labor cost as well as the lowest total cost was in the period
April to August, 1915.

The margin realized on the mining operations from 1913-1918
was as follows : 1913,10.31-0.44; 1914,10.22-0.50; 1915, $0.90-0.50;
1916, $0.38-0.57; 1917, $0.54-0.72; 1918, $0.35-0.39.

Weight of coal in a foot-acre. The amount of coal under a given
area is estimated by the foot-acre and it is directly related to the
specific gravity of a solid mass of the coal. A cubic foot of water
weighs 62.5 pounds. A cubic foot of coal with a specific gravity of 1.3,
a good average for bituminous coal, will, therefore, weigh 81.25 pounds.
This gives 24.6 cubic feet per short ton and 27.5 cubic feet for a long
ton of 2240 pounds. It is often assumed that 0.9 cubic yard of
bituminous coal equals one ton. This is equivalent to 24.3 cubic
feet per short ton and corresponds very well with the figure given
above. Good Pennsylvania anthracite will weigh in the block about
92 pounds and in lump 57 pounds to the cubic foot.

An acre contains 43,560 square feet and a foot-acre that number
of cubic feet. This would yield about 1770 short tons providing it
could all be extracted in mining. The percentage recoverable in
mining will vary greatly according to conditions, such as the thickness
of the seam, its freedom from partings and irregularities, the condition
of the roof and other things, such for example as location beneath a
town or city. Some companies under favorable conditions recover
97 to 98 per cent of the coal while others do not take out more than
50 per cent or about 880 tons per foot-acre. A fair average might be
80 per cent recovered, which gives about 1400 tons per foot-acre.
A 5-foot seam would therefore yield on this basis about 7000 tons
per acre. It should be borne in mind that it may be impossible to
mine, by present methods, more than a small portion of a bed which is
more than 30 feet thick, and an allowance must be made for this
difficulty.

Estimate of coal in seams of varying thickness. It almost in-
variably happens that when a geologist examines a coal property he
must estimate the coal in a number of seams of varying thickness
lying one above another. The best procedure is first to secure a map
of the property outlined on cross-section paper, and then proceed to
divide the property into areas beneath each of which the average

ROYALTIES PAID ON LEASES 259

thickness of the coal is estimated, from all the available data, to be a
certain figure. The whole property is divided up in this way, and the
sum of the tonnages computed for the various areas will give the
total tonnage for the property. The larger the number of areas into
which the property is divided, the greater the probability of securing
an accurate estimate, in most cases. The seams may be lettered or
numbered and then treated separately in dividing the property into
the various areas.

Royalties paid on leases. The royalty paid on coal -lands varies
greatly in different fields. The variation is very much greater than
in the price of coal at the mine in the different fields, and the differ-
ence in royalty demanded does not always correspond to the differ-
ence in the price per acre, which might be demanded for land in
different areas. This is because the rate at which the coal is mined
has an important bearing on the relative income from the royalty and
that from the sale of the land, since the interest on the money and the
taxes amount to a considerable item if the time required for mining the
coal be long. According to Ashley 1 the royalties paid in the Anthracite
region of Pennsylvania previous to 1910 ran up to 50 cents or locally
to $1.00 a ton, and the writer has obtained similar figures for this
field in more recent years, with some running as high as $1.40 a ton.
In the bituminous fields of the state the royalties varied from 5 to
30 cents except in a few cases in which they went up to $1.00 or more
in the Connellsville field. The average for the state was perhaps 10
cents a ton. In Ohio the royalty varied from 8 cents to 15 cents.
In Illinois 2 cents to 25 cents has been paid, and in Indiana 2 cents to
10 cents. The West Virginia royalties which have been reported run
from 8 to 24 cents, the latter in the coke regions. In Kentucky,
Tennessee and Alabama the figures are from 3 cents to 12 J cents and
in Arkansas and Oklahoma 3 to 8 cents. In Colorado, state lands
pay 10 cents and other lands from 8 to 27 cents. On account of the
great local demand for coal in limited areas in Wyoming some roy-
alties have been reported as high as $1.00 a ton, but they usually run
from 3 to 10 cents. Montana royalties are about 15 cents so far as
known, and in Utah some local mines have paid as high as 75 cents.
All these figures have changed rapidly during the last few years of
inflated prices.

1 Op. cit., pp. 9 and 10.

260 PROSPECTING AND VALUATION OF COAL LANDS

In many of the fields where the royalties mentioned above are paid
there is also a bonus and in most cases a minimum yearly royalty is
demanded in the contract. In some states the royalty decreases as
the output increases and in Kentucky it fluctuates with the thickness
of the seam.

CLASSIFICATION AND VALUATION OF COAL LANDS BY THE
UNITED STATES GOVERNMENT

The " Regulations on the Classification and Valuation of Coal
Lands," adopted by the Secretary of the Interior on April 10, 1909,
contain the following clauses:

I. For purposes of classification and valuation, coal deposits shall

be divided into four classes.

A, Anthracite, semianthracite, coking and blacksmi thing coals.

B, High-grade bituminous, non-coking coals having a fuel value

of not less than 12,000 B.t.u. on an unweathered, air-dried
sample.

C, Bituminous coals having a fuel value of less than 12,000 B.t.u.

on an unweathered, air-dried sample, and high-grade sub-
bituminous coals having a fuel value of more than 9500
B.t.u. on an unweathered, air-dried sample.
Z), Low-grade subbituminous coals having a fuel value below
9500 B.t.u. on an unweathered, air-dried sample, and all
lignite coals.

II. Lands underlain by coal beds, none of which contain 14 inches
or over of coal, exclusive of partings, of Class A, B, or C, or
over 36 inches of Class D, shall be classified as non-coal land.

III. Lands containing coals of classes A and B of any thickness
at depths greater than 3000 feet shall be classified as non-coal
lands, except where the rocks are practically horizontal and
the coal lies within 2 miles of the outcrop or point at which it
can be reached by a 30oo-foot shaft.

IV. Lands containing coals of class C of any thickness at a depth
greater than 2000 feet shall be classed as non-coal lands, ex-
cept where the rocks are practically horizontal and the coal
lies within 2 miles of the outcrop or point at which it can be
reached by a 2000-foot shaft.

CLASSIFICATION AND VALUATION OF COAL LANDS 261

V. Lands containing coals of Class D of any thickness at a depth

greater than 500 feet shall be classed as non-coal lands, except
where the rocks are practically horizontal and the coal lies
within i mile of the outcrop or point at which it can be reached
by a 500 foot shaft.

VI. The prices of coal lands of Classes A, B, and C shall be de-
termined on the basis of estimated tonnage at the rate of one-
half cent to i cent per estimated ton for Class C, i to 2 cents
per estimated ton for Class B, 2 to 3 cents per estimated ton
for Class A, when the lands are within 15 miles of a completed
railroad and half that much when at a greater distance; but
the price shall in no case exceed $300 per acre, except in dis-
tricts which contain large coal mines where the character and
extent of the coal are well known to the purchaser. When,
however, topographic conditions affect the accessibility of the
coal the land within the 1 5-mile limit may be given a lower
valuation, but in no case shall it be placed at less than the
minimum, and a graded allowance may be made for increasing
depth, with the same restriction.

VII. The rates per ton in the preceding paragraph are based on
the assumption that only one bed is present. If more than one
bed occurs in any tract of land in such relationship that the
mining of one will not necessarily disturb the other, then for
the second bed there shall be added to the price of the first
bed 60 per cent of the value of the second bed according to the
schedule, 40 per cent of the value of the third bed, and 30 per
cent of the value of each additional bed; but the estimated
price for coal shall in no case exceed $300 per acre, except in
districts which contain large coal mines where the character
and extent of the coal deposits are well known to the purchaser.
Where a bed is over 15 feet thick, the normal value shall be
placed only on 15 feet; the next 15 feet or part thereof shall
be valued at 60 per cent of the normal; the next 15 feet or
part thereof at 40 per cent of the normal and the rest of the
bed at 30 per cent of the normal.

VIII. The tonnage shall be estimated for the purpose of valuation
on the basis of 1000 tons recovery per acre-foot.

262 PROSPECTING AND VALUATION OF COAL LANDS

IX. The price of lands of Class D shall be the minimum provided
by law, $20 per acre when within 15 miles of a railroad and
$10 per acre when at a greater distance.

X. In all valuations of coal lands any special conditions enhanc-
ing the value of the land for coal-mining purposes shall be
taken into consideration.

XI. When only a part of a smallest legal subdivision is underlain
by coal the price per acre shall be fixed by dividing the total
estimated coal values by the number of acres in the sub-
division, but in no case shall this be less than the minimum
provided by law.

XII. When lands which were at the time of classification more
than 15 miles from a railroad are brought within the 1 5-mile
limit by the beginning of operation of a new road all values
given in the original classification shall be doubled by the
register and receiver.

XIII. Except in case of entries now pending or entries made prior
to classification, review of classification or valuation may be
had only upon application therefor to the Secretary accompa-
nied by a showing clearly and specifically setting forth condi-
tions not existing or known at time of examination. 1

In formulating these regulations it was desired that the price should
be such that it would discourage private citizens from buying coal
lands for speculation with a view to holding them for future favorable
conditions, but at the same time that it should not retard the business
of legitimate coal mining. The royalty rate taken as a rough standard
in figuring the price per ton was 10 cents, since it was believed to be
a fair average for the whole country. On the adoption of the above
regulations much land was withdrawn from entry in order that it
should be classified and valued by the Geological Survey. The amount
of land withdrawn from coal entry on November i of that year in the
nine states, Wyoming, Washington, Utah, Oregon, Montana, New
Mexico, Colorado, South Dakota, and North Dakota, amounted to
31,872,171 acres. The area withdrawn from all entry in the same
states on that date was 11,862,576 acres, and the amount of classi-
fied land restored to entry was 35,915,255 acres.

1 Ashley, Op. cit., pp. 37 and 42.

CLASSIFICATION AND VALUATION OF COAL LANDS 263

There has been a growing feeling among government officials and
others interested in coal lands that the public coal lands should be
leased for the purpose of mining only and the title to the land should
rest with the State. 1 Colorado has had for many years a leasing
system on a royalty basis of 10 cents a short ton run-of-mine, less one-
twelfth of the minimum annual royalty which shall have been paid
at the beginning of the year. This minimum royalty is paid whether
any coal is mined or not. Wyoming also adopted the leasing system
in 1907 and in that state an " advance royalty " is paid and is applied
on a royalty of 6 cents on all coal mined, and sold up to 25,000 tons,
5 cents if amount is between 25,000 and 50,000 tons, 4 cents if it falls
between 50,000 and 100,000, and 3 cents if it exceeds 100,000 tons per
annum. The lessee must spend not less than $200 on development
work. As indicated above, Congress has also recently passed a leas-
ing bill which permits the leasing of public coal lands from the
Government.

1 Bain, H. F., Leasing the Federal Coal Lands, Min. and Sci. Press, Vol. 96, p. 73, 1908.
The value of Coal Land. Mines and Minerals, Vol. 29, p. 366.

CHAPTER X

MINING OF COAL

Introduction

The process or mining coal has become a highly developed art and
a detailed description of all methods employed would embrace a very
extensive literature. In this chapter only the main methods employed
are described and reference is made to a few of the larger works in
which the details of the various operations are found. 1 With the
introduction of labor-saving machinery, resulting especially from the
more extensive use of electricity in mines, rapid changes in methods
are taking place and before long the bulk of all coal mined under favor-
able conditions, in the more advanced countries will be cut, broken
and loaded by machinery. The development of large steam shovels
has made it possible to strip many coal seams formerly out of reach
in open pit mining and to mine them on the surface, while the
working out of the thicker seams underground necessitates the mining
of thinner seams. In this work the use of mechanical conveyors
and other labor-saving devices is becoming more common.

Mining Methods

The main methods employed in coal mining may be classed as (i)
Open work and (2) Underground, or dosed work. The first is fre-
quently known as stripping or open-pit mining. The underground
methods may be divided into Room-and-pillar and Longwall methods,
and there are several modifications of each of these.

STRIPPING METHOD

In areas where a good seam of coal underlies a thin overburden
it pays to strip off the covering. The depth to which this stripping
may be profitably carried depends upon many factors. It has been

1 Coal miner's pocketbook, McGraw Hill, 1916. Peele's Handbook for mining en-
gineers, John Wiley & Sons, Inc., 1918. Practical coal mining by W. S. Boulton, London,
1907. Vols. 1-6. Colliery working and management, Bulman and Redmayne, 1912.

264

STRIPPING METHOD

265

considered in the past that a foot of overburden could be removed
by hand for each foot of coal obtained. Most stripping is done at
the present day, however, by the large steam shovel of ordinary type,
the rotary shovel or the dragline excavator. In Illinois hydraulic
means are employed to some extent in stripping. The proportion
of overburden to coal which may be profitably removed has therefore
increased to from 3 to 6 times the figure stated. The proportion will
vary greatly according to the grade and the price of the coal and the
nature of the overlying rock. A heavy, little-jointed sandstone or
limestone which requires blasting, or a loose rock which is full of water
and runs readily may increase to a large degree the relative cost of
stripping.

FIG. 83. Stripping on the Mammoth Seam near Hazleton, Pa. (Photo by E. S.

Moore.)

In the anthracite region of Pennsylvania extensive stripping oper-
ations are carried on, especially in the district around Hazleton where
the Mammoth seam is thick, (Figs. 76 and 83). In some places this
seam runs from 50 feet up to 100 feet or more, where it is duplicated by
folding, and an overburden up to 90 feet in thickness has been removed,
while some of the projected strippings will require the removal of
nearly 200 feet of overburden as, for example at Locust Mountain.
A great deal of coal is obtained by this method which could not be
obtained by underground mining, especially in those areas where

266 MINING OF COAL

the early mining operations left much coal in the ground and a
great deal of it in such condition that underground mining is very
difficult, dangerous or even impossible.

In some of the bituminous fields of the United States open cuts are
extensively worked, particularly in Alabama, Missouri, Kansas, In-
diana, Ohio, Pennsylvania, Illinois and Oklahoma. In Missouri over
one million tons, or 21.6 per cent of the coal mined in that state in
1916 was mined in this way. Over 12 per cent of the coal mined in
Indiana and a considerable amount of that raised in Alabama is worked
by this method.

After the stripping is done the coal is usually dug by steam shovels
of special type, known as rotary shovels, but in a few cases it is dug
by hand.

The main advantages of the stripping method are in the absence
of squeezes, falls of roof and dangerous gases with accompanying
explosions. There is no necessity for timbering or lighting, and the
work may be more easily directed. Experienced men are not neces-
sary except for the management of the steam shovels, and in case of
closing down operations the damage by flooding of the pit is not
usually so great as the damage suffered by an idle mine. The dis-
advantages are the necessity of ceasing work in very stormy weather
and the collection in the open pits of so much water, and, in the colder
climates, of snow. It is difficult to dispose of the overburden in some
regions and the abandoned pits are objectionable, but probably not
much more so than a surface area which is extensively caved after the
mining of shallow seams.

UNDERGROUND WORKINGS

MINE OPENINGS

In order to reach the coal which lies too deep for stripping oper-
ations a tunnel or drift is driven, or a slope or shaft is sunk. A tunnel
is typically open at both ends but the term is often applied to an
opening driven horizontally or nearly so across the measures. In
coal mining, a drift is usually regarded as an opening driven from the
surface in the seam but the term is also used in some cases where the
opening does not reach the surface. A shaft is a vertical mine opening
driven from the surface. If it is driven from one seam to another it

ENTRIES, HEADINGS, OR GANGWAYS 267

. i

is known as a blind shaft. A slope is an inclined opening usually
driven on the coal seam and used as a haulage or other roadway.

Shafts. A shaft should be placed where it will best serve the
maximum portion of the area to be mined and it should be kept away
as much as possible from areas which are faulted, highly squeezed
or subject to flooding. A shaft may be timbered, bricked, concreted
or lined with metal. Timber is commonly employed but many of
the modern shafts in large mines are concrete lined while brick is used
in many mines, especially in Europe. The advantage of brick or
concrete over timber is in their greater durability, in the absence of
danger from fire, and, in the case of air shafts, in the fact that they
offer much less friction to the air currents since the timbers tend to
create local eddies in the current and thus increase resistance to
movement.

The shape of the shaft varies with the conditions. A timbered
shaft is, as a rule, rectangular while a brick or concrete shaft is usually
made circular or elliptical. The size depends chiefly upon the pro-
posed output of the mine, the size of the mine car to be employed
and the possibility of the formation of ice in the compartments in
winter. The width of the cross section may be from 5 feet to more
than double that width, and the length may exceed 50 feet where
there are a large number of compartments used in hoisting a big
output.

In most shafts there is a compartment set apart for pipes and
ladders while the others are used for hoisting.

In sinking a shaft the same methods are employed in coal mining
as in metal mining and include the blasting of the rock and its re-
moval by hoisting with windlass or steam hoist. Where the rock
is not firm or where quicksand or other running ground is encoun-
tered special methods such as piling, freezing or cementing must be
employed. A shield may be used in some cases to protect the work-
men from falling rock.

The laws of most states require at least two separate openings to
all coal mines so that in case of accident men may have a means of
escape.

THE ROOM-AND PILLAR-METHOD

Entries, headings, or gangways. As the term implies this method
consists in working out rooms, chambers or breasts, in the seam, leaving

268

MINING OF COAL

ENTRIES, HEADINGS, OR GANGWAYS 269

portions of the coal between these rooms in the form of pillars to sup-
port the roof. The portion of the seam which is to be mined from a
certain shaft or slope is first split up into a number of sections by
driving passages from the shaft bottom or from the slope as the case
may be, (Fig. 84). These passages are known as main entries or
main headings in the bituminous mines and as gangways in the an-
thracite mines of America, and they usually run to the border of the
property. They are as straight as possible so as to avoid turns in
track or sudden changes in direction of the air currents, and where
used for air courses the perimeter should be as small as possible in
proportion to the area so as to reduce friction of air current to a mini-
mum. The nearer a square is approached the less the perimeter for
the area enclosed. They are about 6 feet high and from 6 to 21 feet
wide, according to the thickness of the seam, the nature of the bottom
and roof of the seam, the amount of output from the mine and other
factors. If the roof and bottom are bad it is more difficult to carry
a wide entry and if the seam is too thin so that the roof must be
brushed down by taking down a lot of draw slate there must be an
entry wide enough to furnish some storage space for the waste rock.
It usually costs much more to drive narrow entries than wide ones
in proportion to the coal taken out as the former operation is classed
as narrow work and a higher charge is made for all work so classed.
The size of the area mined from one shaft where the seam is flat
will run from several hundred to two thousand acres or more depend-
ing upon conditions, and some main entries are, therefore, of great
length. They are timbered, bricked or concreted where necessary
to properly support the sides and roof. Timber is more commonly
used but concrete is now being extensively adopted in the larger
mines for at least the part of the entry near the shaft or slope.

In driving main entries they are usually driven on the dip of the
seam, if the seam is inclined, and if it be nearly flat such factors as
drainage, direction of horsebacks, direction of joints in the coal or its
cleat, and direction of fractures in the roof of the entries affect the
direction. From the main entries cross entries, cross headings, or
butts are driven, usually at right angles to the main passages. There
are some important considerations in laying out the cross entries or
butt headings. They must drain properly to the main headings and
if possible any grade should be used to advantage in hauling the coal.

270 MINING OF COAL

In case a syncline or " swamp " occurs in the mine the headings
should be run so that the rooms may be driven on the rise from the
entry and the coal thus worked down grade to the main haulage lines.
In inclined seams the headings are driven so that they follow closely
the strike of the seam, allowing for drainage, and each section of the
mine in which one or more of these headings is driven off the slope is
known as a lift or level. This term includes all the workings lying
at approximately the same level and connected with the slope or shaft
at the same elevation.

Entry systems: The number of entries varies greatly in the mines
of different regions. There are single, double, triple, quadruple, and
even sextuple-entry systems. The first is seldom used and is not
applicable to a large mine. In it a single entry is driven and it serves
as the haulageway and intake air course. It is inefficient because an
accident in the entry may cut off the circulation of air, the haulage,
and the escape of men from the mine.

The double-entry system is very commonly used in America and as
indicated by the name the main and cross entries are all driven in
pairs. This increases the efficiency of the mine as a double track
increases that of a railroad. If one entry becomes blocked the air
current and the haulage may be shifted to the other, (Fig. 84 and
Plate IX).

The triple-entry system is also frequently used and it has an ad-
vantage in that the central passage may be used as the main haulage
route and at the same time the intake air course. The other two
entries are the return air courses for their respective sides of the mine.

In the four-entry system there are four entries driven side by side;
this system is frequently adopted, especially for gaseous mines and
those with a large output (Fig. 84). For those mines where endless
rope haulage is used it has an advantage as one entry may serve as a
haulage road for loaded cars and the other for empties, while the
other two are the return air courses. Several different arrangements
are possible as one entry may be used for a manway and intake air
course, one as a haulage road and intake and the other two as return
air courses, or they may be divided so that the four entries are oper-
ated as pairs.

In all these systems where two or more entries are used the entries
are connected by cut-throughs , break-throughs or cross cuts, which

ROOMS, CHAMBERS, OR BREASTS 271

are openings about the same width as the entries and driven at right
angles to the entries, through the pillars separating them. When
one of these openings is driven at an inclination less than 90 to the
entry it is known in some localities as a shoofly, (Fig. 84). The
distance between these openings varies with the law requirements of
the region, the gaseous nature of the mine and other local conditions.
In the entries, spaces must be provided for the temporary storage of
cars where they are collected from the working places and made up
into trips. These track areas are known as sidings, partings or lyes,
and where single track is used for haulage the siding where the cars
turn out to pass is known as a turn-out or pass-by.

Rooms, chambers, or breasts. The rooms, chambers or breasts
are openings in the seam turned off the cross-entries and separated
by pillars, (Fig. 84). These rooms are laid out according to a definite
system and at stated intervals. The end of the room where the coal

FIG. 85. Rooms driven at inclination to the entry in double entry mine.

is being mined is known as the face or working face and the side of the
room or entry along a pillar is the rib. The terms inby and outby
serve to indicate the direction in the room, the former meaning toward
the face and away from the entry and the latter the opposite direction.
When a room is begun an opening known as the neck or mouth is
made from the entry and about the same width as the entry. This
is usually at right angles to the entry in flat or steeply pitching seams,
but in gently inclined seams the rooms may be inclined less than 90

272 MINING OF COAL

to the entry and thus secure a more gradual rise for hauling cars to
the face, (Fig. 85). Where the rooms are driven at such an angle
their necks must be longer in order to leave sufficient coal in pillars
to protect the entry. The direction of the room may also be influ-
enced by the fractures in the roof and by the cleat in the coal. There
are several terms describing the relation between the direction of
these joints and the direction of the room. When the face is parallel
to the main, or face cleat, and the rib at right angles to it the position
is known as face on. The opposite to face on is end on, the position

in which the face is at right
angles to the face cleat and
parallel to the butt cleats.
Half on is the term used where
the face of the room makes an
angle of 45 with the face cleats
and short horn where it makes
an angle of more than 45. In
driving long horn the face of the
room lies at an angle less than
45 to the face cleats. These

FIG. 86. - Double room and break-throughs. vari US Psitions have their ad-

vantages under different con-
ditions because the coal breaks more readily and leaves more lump
if mined from a certain direction with relation to the cleats. The gas
may escape from the coal more gradually if the face lies across the di-
rection of the main joints rather than parallel to them.

When the neck of a room has been driven a sufficient distance from
the entry, varying from 6 to 25 feet, the room is widened out on one
side of the neck at an angle of 90 or less, usually less, (Fig. 84).
This side is known as the gob side because the waste rock is usually
stored in it and the track is laid along the opposite side. The width
of the room will depend upon such factors as the weight of overlying
strata, the. character of the roof and bottom and the thickness of the
seam. A common width is about 20 feet, but it may run from 12
feet up to 40 feet or more. The length of the room usually lies be-
tween 150 and 300 feet although rooms are sometimes as much as
600 feet in length. A common length is 250 feet. The presence of
gas will usually affect the length of the room to some extent and tend

PILLARS 273

to shorten it. The rooms are connected by cut-throughs , or break-
throughs, to permit the circulation of air and the movement of the
workmen, and in some cases a series of these in line may serve as a
haulage road. The more gaseous the mine the more numerous the
break-throughs should be. In many fields their number is fixed by
law. In the bituminous region of Pennsylvania they cannot be more
than 35 yards nor less than 16 yards apart.

In some mines double rooms are driven, leaving a pillar of coal be-
tween the double necks, (Fig. 86). The main advantage of the
double room is in the more extensive working face provided. If
there be much waste rock it may be gobbed along the center of the
room leaving the tracks along the ribs on either side.

Pillars. The several types of pillars in a coal mine comprise :
the ordinary pillars left between entries and between rooms or breasts;
chain pillars; shaft or slope pillars; and barrier pillars. A chain
pillar is a long wide pillar left along an entry or gangway from which
rooms are being driven to protect that opening, and it may be cut
through by a number of break-throughs. A shaft pillar or slope
pillar is left around a shaft or slope in each coal seam through which
the shaft or slope passes, to protect the shaft or slope and the build-
ings or other structures on the surface from damage. A barrier pillar
is left along the border of a property to protect adjacent lands on
either side of a property line from caving and from water or gas.
The term is also applied to a pillar left in a mine to protect a certain
portion of the mine from gas or water or to separate for some other
reason this portion from the remainder of the mine.

Size of pillars: The size of any of these pillars depends upon vari-
ous conditions and can only be determined from experience in the
region being worked. The greater the inclination, depth and thick-
ness of the seam, the greater the quantity of water present, the weaker
the roof and bottom, the more friable the coal, the more faulted the
overlying strata, and the longer the pillars must stand, the larger
they must be, other things being equal. The approximate weight
of the overlying strata may be figured by averaging the specific gravity
of the rock and computing the weight of the column of rock of the
proper size and depth, but even then the effects of arching or bridging
of the heavy beds in the series will not be taken into account. The
average specific gravity of sandstone may be taken as 2.3 and that of

274

MINING OF COAL

PILLARS 275

shale as 2.5, which makes a cubic foot of sandstone weigh about 140
pounds and a cubic foot of shale approximately 160 pounds.

The distance between entries is usually made from 20 to 60 feet.
Under certain conditions it is necessary to leave extra entry pillars
to protect the entry, and these may be very wide, sometimes exceed-
ing 100 feet. The room pillars vary from 6 to 90 feet in width in
various mines, depending upon conditions and the methods adopted
in these mines. The pillars are much wider at the stump, which lies
between the necks of the rooms than elsewhere. A common width is
20 to 30 feet for these pillars.

The width of barrier pillars, like that of all others, varies with the
conditions, the three main ones being the inclination and depth of
the seam and the amount of water in the adjacent workings. A rule
generally used as a guide by inspectors and engineers in the anthracite
region of Pennsylvania is as follows: Multiply the thickness of the
deposit in feet by i per cent of the depth below drainage level and add
to this 5 times the thickness of the bed. In the bituminous region of
Pennsylvania the mine law fixes the width of the pillar according to
the conditions relating to water pressure.

In some of the steeply pitching anthracite seams it is probably
impractical to attempt to leave a barrier pillar which will be capable
of supporting the load and holding back the water in deep basins,
when the seams have been extensively mined. The oxidation of
the coal where circulating water comes in contact with it tends to
weaken the pillar in time.

There are many rules for establishing the size of shaft pillars. As
in the cases of the other pillars mentioned it is necessary to leave a
large margin of safety as it is extremely important to protect the shaft
bottom and the structures on the surface from any damage. Among
the rules for the size of shaft pillars which are most generally ac-
cepted is Dron's, which allows for a good factor of safety. Dron's
Rule is as follows: Draw a line enclosing all surface buildings that
should be protected by the shaft pillar. Make the pillar of such a size
that solid coal will be left over the whole area enclosed by this line and
for a distance beyond the line equal to one-third the depth of the shaft.
The formula for computing the diameter of the shaft pillar by this

2d
rule is as follows: D = s -\ , where 5 is the diameter of the circle

276 MINING OF COAL

or square enclosing the structure on the surface and d is the depth of
the shaft, in the same units of measurement.

Some of the other rules employed are as follows:

Andre's Rule : Minimum diameter of circular pillar or side of square
pillar should be 35 yards to a depth of 150 yards. Add 5 yards for each
25 yards of additional depth.

D = 35 + 5

Mining Engineering Rule: Radius of circular pillar or half side
of square pillar, in yards is equal to 20 yards plus one-tenth of the prod-
uct obtained by multiplying the depth of shaft, in yards, by the square
root of the thickness of the seam in yards.

^ ( , d x Vt\

D = 2 [ 20 H ) =

V 10 /

d x Vt\ . d x Vt
40 +

where d = depth of shaft and t the thickness of the seam.

Foster's Rule : Radius of circular pillar, or half side of square pillar
in feet, is equal to 3 times the square root of the product of the depth of
cover, in feet, and the thickness of the seam in feet.

Hughes Rule: For the diameter of a circular pillar or the side of
a square pillar allow i yard for each yard in depth.

Central Coal Basin Rule: Leave 100 square feet of coal for each
foot that the shaft is deep, a main entry of average width being driven
through this pillar. If the bottom is soft the result is increased by one-
half.

D = Vioo d

Modifications of The Room-and-Pillar Method

The pillar-and-stall system. This system is also known in some
places as bord-and-pillar and post-and-pillar, although the systems
are not the same in all respects. The pillar-and-stall system differs
from the method already described in the smaller size of the rooms in
proportion to the size of the pillars. The stalls are narrow rooms
usually 10 to 15 feet wide with pillars about the same size in some
cases. In other cases the rooms are driven about 10 feet wide on
loo-foot centers and the pillars are then split a great number of times.
In some cases double stalls corresponding to double rooms are driven.

ANTHRACITE MINING IN PENNSYLVANIA 277

This system is used to advantage in some seams with bad draw slate
and a bottom rock inclined to heave. In some places the stalls are
driven full width from the entry without a neck. One form of this
system is used in the Connellsville region of Pennsylvania.

The panel system. The principle adopted in the panel system is
to divide the area to be mined into square or rectangular blocks by
entries driven at right angles to each other, (Fig. 87). These blocks
are subdivided into a large number of smaller blocks and thus the

FIG. 87. The panel system.

original section is worked out as a unit. A large solid pillar is usually
left surrounding the panel on three sides, serving as a barrier in case
of fire or accident and controlling the air circulation. The system
has the disadvantage of much narrow work but the advantage of
giving complete control of the ventilation in that section of the mine
and of permitting the block to be handled as a separate unit in case
of accident.

Anthracite mining in Pennsylvania. Since special methods must
be employed in seams dipping more than 10 a description of some of
the methods employed in the anthracite region of Pennsylvania will
serve to illustrate the main variations from those employed in flat-
lying seams. In general the room-and-pillar method is used, but the
rooms are known as breasts or chambers and the entries as headings

2 7 8

MINING OF COAL

or gangways. The breasts are driven to the rise and nearly up to the
next higher gangway, (Fig. 88).

One of the main problems confronting the miner in inclined seams
is that of transporting the coal in the breast from the face to the gang-
way. The following methods are employed: If the seam does not
pitch more than 10 or 12 and the breasts are driven at an inclination

to the pitch the car may
be taken to the face and
lowered by hand, by
mule or motor. These
means cannot be em-
ployed in a seam pitch-
ing more than 5 or 6 if
the breast be driven on
the full pitch. If the
breast be driven on the
full pitch the car may
be lowered by windlass
up to 10 or 12 inclina-
tion. Jig roads are also
used under similar con-
ditions.

The buggy system.
The buggy system is
often used in thick
seams where there is
plenty of head room.
This system consists in

the use of a small car which can be taken to the face by hand or by
aid of a windlass where the seam pitches from 10 to 18. The coal
is loaded on the buggy, taken down the breast and dumped on a
platform, from which it is shoveled into the mine car in the gang-
way. In some cases two buggies are used and the coal is trans-
ferred from one to the other and thus lowered by stages. This
method is costly in labor and coal broken.

Chutes. In seams dipping between 1 5 and 30 the coal is
usually sent down sheet-iron chutes to the gangway. These chutes
are laid in the center of the breast with a row of props along either

FIG. 88. Mining anthracite in Pennsylvania in
steeply dipping seam. (After H. H. Stock, U. S.
Geol. Survey.)

CHUTES

2 79

side and the gob is stored between these props and the ribs. The
men travel along the chute. When the seam dips more than 30
the coal will usually slide of its own weight and it is necessary
to place an obstruction at the bottom of the chute in the neck of the
chamber to hold the coal back. The structure employed is known
as a battery, and a breast with such an arrangement as a battery breast,
(Fig. 89): The coal is drawn out through the battery at such a
rate that plenty of broken coal remains in the breast to permit the
men to stand upon it and work at the face. This avoids the necessity
of building a timber stage on which to work. In some cases the
breasts are driven with double necks and two batteries are then

constructed, (Fig. 90). This arrange-
ment has the advantage where the seam
is steeply inclined, of leaving a large
pillar in the center of the lower end of

FIG. 89. Single battery breast in FIG. 90. Double battery breast,

anthracite mine.

the breast to support the weight on the battery. In the battery
breasts a manway must be provided as a separate opening driven
through the coal or as an opening through the battery. In the
breasts the men travel along the chute which is lined with posts
securely set into the floor and roof of the seam.

In the working of contiguous seams or of seams lying parallel and

280

MINING OF COAL

close together but separated by more than about 3 feet of rock, the
coal in the upper seam is carried to the gangways in the lower seam
through rock chutes, (Fig. 91). If there be less than about 3 feet of
rock separating the seams they are usually worked as one seam with
a parting, and the rock is mined out. Where contiguous seams are
worked the working of the upper seam is usually completed first and
the pillars robbed before the underlying seam is worked beyond the
driving of gangways and airways.

FIG. 91. Method of working contiguous seams through a horizontal rock tunnel.
(After H. H. Stock, U. S. Geol. Survey.)

Pillar Drawing

During the first mining a large portion of the coal is left in the
pillars and it must be extracted later. The process of removing the
coal in the pillars is known as robbing pillars or pillar drawing.
It is one of the more hazardous features of mining operations and

THE LONGWALL METHOD 281

the work should be attempted only by the more experienced
miners. The percentage of coal left in the pillars after the first work-
ing varies from 30 to 65 per cent of that originally in the seam, and
in some cases where the thickness of the seam is favorable, the gas
not excessive, and the roof and bottom good, as much as 98 per cent
has been removed by final working.

There are several systems of robbing pillars and the one adopted
depends largely upon the local conditions. In some cases a break-
through is made at the inby end of the pillar and the pillar is gradually
removed until only the stump is left near the entry. Props are used
to partially support the roof as the coal is removed and as the work
advances the props are recovered and the roof allowed to cave. Care
must be exercised in supporting the roof so as to keep sufficient pres-
sure on the coal to help break it but not enough to crush the pillar.
The roof should be broken at the stumps if possible, so as to relieve
the weight on the entry pillars. Gas should not be allowed to collect
in the gob for an indefinite period as it may escape into the workings
or take fire. Another method of robbing pillars consists in splitting
the pillars one or more times and then drawing them back as described
above.

In some mines the pillars are drawn out in panels and in others
the workings are driven to the edge of the property and the pillars
drawn back on a retreating system. In any case the ends of the
pillars being drawn back should be kept in a nearly straight line so
as to keep the roof supported and also to let it cave in a systematic
manner, (Fig. 84). This lessens the danger to the miners and avoids
the loss of coal.

THE LONGWALL METHOD

There are two main systems in longwall mining and several modi-
fications of these systems to suit particular conditions. The systems
are known as the advancing and retreating systems. In the former
the workings are advanced from the shaft pillar toward the border
of the property and in the latter the main entries are driven to the
border of the property and the workings are then carried back toward
the main shaft. The main features of the longwall method are the re-
moval of practically all of the coal as the face advances and the main-
taining of a continuous working face around the workings, (Fig. 92).
The waste rock is used to fill up the space from which the coal has been

282 MINING OF COAL

removed and the roadways are maintained by pack-walls on either
side of them, made of waste rock. These piles of rock are known as
the road packs and those in the areas between the roads as gob packs.
The main roads run diagonally from the shaft pillar like the spokes of
a wheel, and the intervening areas are subdivided into smaller and
smaller sectors by subsidiary roads.

Overcasts shown thus: X
Curtains shown thus ;

FIG. 92. Plan of a longwall mine showing direction of ventilating current. (After
Swift; from Bull. 13, III. Geol. Survey, University of 111. and U. S. Bur. of Mines.)

In this method little of the coal is blasted from the face, the roof
pressure being used to break it down after the coal is undercut. It
is necessary therefore that the face be advanced uniformly and con-
tinuously.

This method is particularly adapted to thin seams where the roof
settles and the bottom tends to heave, since the waste rock is used
for packing and the coal can all be removed in the first working.
It also leaves the surface in better condition than the room-and-

THE LONGWALL METHOD

283

pillar method because the strata settle more uniformly. A larger
percentage of the coal can be extracted in most cases than with the
other system. Less timber is needed for roadways than in other
methods and as a rule this method brings quicker return for capital
and labor.

FIG. 93. Plan of longwall mine with auxiliary permanent entries. (After S. O. Andros.)

The disadvantages of the longwall method lie in the fact that more
experienced miners are needed to operate the mine successfully. A
section of the mine cannot be controlled as with the other methods
and the mine suffers more from idleness or from irregular work of
men at the face. It is more difficult to get into operation and a great
deal of trouble is often encountered in getting the roof to break prop-
erly around the shaft pillar or at the limits of the property as the case
may be. It is only successful where there is plenty of waste rock,
although in France it is employed where rock must be brought in

284

MINING OF COAL

from the surface in great quantities. There are immense quarries
in central France from which the rock is taken for this purpose,
(Fig. 96). This increases the expense considerably. In the United
States the longwall method is used comparatively little. There are
a good many longwall mines in Colorado and some of the other west-
ern states, a number in Illinois and a few in some of the eastern
states. Certain modified systems used in the anthracite region of
Pennsylvania are known as the chamber longwall, lateral longwall and
block longwall systems. These are operated on a rectangular or sort
of panel arrangement, (Figs. 94 and 95).

Gangway

.o-

) r^ it ^ i ) r )( i i ic

Airway in Coal Only |_

Pillar

Oj
~f

Pillar i

It B -

iYlf

* <5 ** i

p DH

si .?

ra @

fill

Pillar Left in Place

^
^
P

**'

i B ij

f ill * !?

Bl .1 = f.

T I 1 S g 1 i

t Mr* if

S 5' '"fl

i II 1 i j,

F |- | . A

1 H S @

tint

i @ e

Gangway^

p a

Cars

J I If 1 (

f " "^

( J 1

Airway in Coal Only

FIG. 94. Block longwall system. (By courtesy of the D. & H. Company,

Scranton, Pa.)

Mining in thick seams. When seams are very thick it is neces-
sary to mine them in benches or with some sort of shrinkage stope
system. The system which has been most successful is a modified
form of the longwall in which the seam is worked in benches and the
open spaces packed full of waste rock, (Fig. 97).

Breaking the Coal at the Face

Several methods are employed in breaking the coal at the face.
When the longwall method of mining is adopted the coal is undercut

BREAKING THE COAL AT THE FACE 285

by a longwall machine and the roof is allowed to settle gradually so
as to break down the coal. In the room-and-pillar method the coal
is undercut by a coal cutting machine or by miners' picks and is blasted
or wedged down, (Fig. 98). In many cases the coal is sheared as
well as undercut. Shearing consists in making a vertical cut along
the side of the room or entry as the case may be in order to keep the
wall straight and uniform. Some of the latest machines will not

FIG. 95. Development of a longwall operation in the anthracite region.
(By courtesy of the D. & H. Company, Scran ton, Pa.)

only undercut the coal but also shear it, and it is expected that in the
near future they will be so constructed that they will also success-
fully break down the coal. The depth of the channel which is cut
along the bottom of the seam, or along a parting in the coal as the
case may be, may reach 6 feet or more, but it depends somewhat upon
the nature of the coal and roof pressure. When it is done by hand it
must be wide enough to permit a man to lie in it on his side and work

286 MINING OF COAL

a pick, the seam above him being kept from closing down by a short
prop. After the coal is undercut it is shot down or wedged down.
In some cases coal is shot from the solid, and fhis is necessary in
many anthracite mines. This method has the disadvantage of
breaking the coal up so that much more slack and less lump coal
results. There is also more danger in firing owing to the heavy
charges necessary to blow the coal down. The production of a
greater percentage of slack does not matter so much if it is to be
used for coking but it lowers the value of the coal very greatly for
domestic and steaming purposes. A great deal of care and judg-
ment is necessary in placing the holes which are made by augers or
hammer drills, as their depth and arrangement affect the amount of
coal shot down, the conditions in which the broken coal occurs and
the safety of the miners, especially when black powder is used.

Mining Machines

There has been a rapid development in coal mining machines in
recent years. The latest coal-cutter has been so developed that it can
undercut and shear the seam, can cut out a sulphur band or a parting
in the seam and can be operated much more readily than the earlier
types. There are also loading machines which apparently work
quite successfully under certain conditions. The tendency has been
to get away from the pick machines, or punchers and adopt the con-
tinuous cutting types. The application of electricity has been re-
sponsible for a great development in mining machines and it is now
possible to use electric machines in gaseous mines. According to the
latest report of the Department of Mines of Pennsylvania, the per-
centage of bituminous coal mined in this state by compressed air
machines in the year 1899 was 21.22, and in 1917 it was 9.03. In the
same years the percentages mined by electrical machines were 18.38
and 45.14 respectively. In the same years the percentages mined by
hand were 60.40 and 45.83.

The use of cutting machines in the anthracite region has developed
more slowly than in the bituminous region of Pennsylvania, owing
to the difficulty in cutting the harder coal and in moving the machines
on the steep pitches, but the machines are now successfully used in
parts of the region.

MINING METHODS IN FOREIGN COUNTRIES

287

It seems probable that we will see a machine in the not far distant
future which will undercut, shear, break down and load the coal
where the conditions are favorable.

Mining Methods in Foreign Countries

Europe. The longwall method is much more generally used in
Europe than in America, and on the European continent it is used
almost entirely. According to G. S. Rice 1 the typical American room-
and-pillar method is not used in Europe except in a few places in
Wales, where it is known as the pillar-and- (single) -stall method, and

FIG. 96. Open cut at Commentry, France, from which coal has been mined and most
of the rock used to fill the mines. (Photo by E. S. Moore.)

in Upper Silesia where it was formerly used rather extensively but is
now largely abandoned for the longwall method. The pillar-and-
double-stall method was formerly used to some extent in Scotland
and in Wales but it has also been nearly abandoned for the longwall
method. In South Staffordshire a method known as the square-
chamber method has been used in the Ten Yard seam. In this method
the coal is worked by chambers 46 yards wide and up to 200 feet long
with thick pillars between them. Four to six coal pillars are left
standing in rows through the chamber.

1 Rice, G. S., Coal-pillar drawing methods in Europe. Trans. Amer. Inst. Min.
Met. Eng., New York Meeting, Feb. 1921.

288 MINING OF COAL

The bord-and-pillar or stoop-and-room method is common in the
north of England, in Scotland and to a lesser extent in Wales. In
Upper Silesia it is used in a modified form where the hydraulic sand
filling system is in use in the thick seams. The writer has visited
mines near St. Etienne, France, where the modified longwall method
was being used and the waste rock of the mine was supplemented by
rock brought in from the surface so that the space mined out could
be completely filled up as fast as the coal was removed, (Fig. 96).

Australia. 1 On this continent the pillar-and-bord system is very
largely used although the longwall method is found in a number of
mines. In several places both methods are used in the same mine.

FIG. 97. Bench working in thick seams, with stone packs.

In some mines one method is used in one seam and the other method
in an underlying seam, depending upon the thickness of the coal, the
abundance of waste rock and other factors.

Mine Haulage

Haulage in mines is performed by animals, electric motors, com-
pressed air locomotives, steam locomotives and cables. There are ad-
vantages in all these sources of power under certain conditions. Some
companies have successfully taken the cars to and from the face with
a motor while others have found it uneconomical to use a motor for
other purposes than hauling trains of mine cars considerable dis-
tances. In the latter case a mule is used for gathering the cars into
trains. Whether a motor may be used successfully in gathering seems
to depend very largely upon the thickness of the seam and the ease
with which the tracks are kept open and in good condition.

Rope or cable haulage is of two types, endless and tail. In the

1 Power, F, Danvers, Coalfields and collieries of Australia. 1912.

HOISTING 289

former type the cable runs continuously and the car is arranged
so as to grip the cable. This works successfully in some mines but
unsuccessfully in others. The straightness and regularity of the
entries has a good deal of influence on this system. With the tail
rope the cars are hauled in opposite directions by separate ropes.

Conveyors are now being used successfully in some mines, espe-
cially in some of the thin seams in the anthracite region of Pennsyl-
vania. Scrapers have also been used to some extent in gathering

FIG. 98. Sullivan Ironclad alternating current mining machine in operation
undercutting a seam. (By courtesy of the Sullivan Machinery Co.)

coal. A remarkable conveyor, about eight miles in length is being
installed by the H. C. Frick Company for transporting to the river
the coal from several mines. It runs underground and the great belt
is driven by a series of motors connected with each other by auto-
matic control systems. It may revolutionize this type of trans-
portation.

Hoisting

Hoisting of coal is usually accomplished by raising the mine car to
the tipple and dumping it. Some mines, however, have operated

2 go

MINING OF COAL

lo-ton skips very successfully. 1 Some of the advantages claimed for
skip hoisting over a self-dumping cage are: a larger capacity for
coal and rock; smaller shaft necessary; lower rope speed and power
consumption; and fewer men. Some of the objections commonly
made to skip hoisting are: the greater breakage of coal, although
this does not appear to be necessary; excessive dust raised by dumping
at bottom of shaft; necessity of a cage for hoisting men and materials;
difficulty in docking and inspecting the coal; and difficulties in hand-
ling waste rock on the surface.

FIG. 99. Electric haulage. A trip leaving the mine of the Ebensburg Coal Company.
(Photo, by courtesy of J. F. Macklin, Pres. Ebensburg Coal Co.)

Mine Gases 2

Ordinary pure air contains about 20.93 P er cen t by volume of
oxygen, 79.04 per cent nitrogen, 3 parts in 10,000 of carbon dioxide
and small amounts of argon, helium and other gases. Water vapor is
present in varying amounts depending upon temperature and pressure
and the presence of water in the neighborhood. The oxygen is the
most active chemical agent in the atmosphere and it unites with

1 Allen, A., and Garcia, J. A., Skip hoisting for coal mines. Trans. Amer. Inst.
Min. and Met. Eng., New York Meeting, Feb. 1921.

2 Beard, J. T., Mine gases and explosions. John Wiley & Sons, Inc., 1908.

CARBON DIOXIDE 291

metals causing them to deteriorate, as in the case of iron rusting.
Oxygen is given off by plants, but when animals breathe slow com-
bustion occurs as in a fire and the carbon in their systems unites with
the oxygen to produce carbon dioxide. Nitrogen is an inert gas and
serves the purpose of diluting the oxygen of the air.

In some mines the air is fairly pure and an open light may be
carried without danger. In others there is an abundance of methane
and carbon dioxide and dangerous quantities of carbon monoxide
and hydrogen sulphide, making it unsafe to enter the mine at all
with an open light and dangerous to enter it with a closed light unless
the ventilation is good.

Carbon dioxide. Carbon dioxide (CO 2 ) has a molecular weight
of 44 and a specific gravity of 1.529. Being heavier than air it natur-
ally settles to lower levels when with lighter gas, and this explains
why animals may be overcome in low places where this gas has col-
lected while at higher points in the same region they may be quite
safe. It should be borne in mind, however, that this may not always
be true for the location of the gas in mines since the air currents and
the source of the gas may have some influence on its gathering point.
It is a product of combustion from fire and the lungs of animals. It
may also be given off during the decay of vegetal matter and this
explains the presence of a considerable amount of it in the mines where
oxidation of the coal is in progress and where it has been imprisoned
in the coal seam since its formation from the altering vegetal matter.
A certain amount is given off by the breathing of the men and the
horses or mules in the mine and by the burning of the lamps.

Black damp or choke damp is a mixture consisting chiefly of nitro-
gen and carbon dioxide with a little oxygen. 1 It is not explosive or
poisonous but its danger lies in the fact that it excludes the oxygen
so that a sufficient quantity does not reach the lungs of animals.
According to W. G. Duncan, average black damp contains 85 to 95
per cent nitrogen and the remainder is chiefly carbon dioxide. The
average composition of the mixture is about 90 per cent nitrogen
and 10 per cent carbon dioxide. It is, therefore, impossible for an
animal to live or a light to burn in this gas.

The presence of carbon dioxide may be detected by an ordinary

1 Burrell, G. A., Robertson, I. W., and Oberfell, G. G., Black damp in mines. U. S.
Bur. Mines, Bull. 105, 1916.

2Q2

MINING OF COAL

lamp or candle which requires 17 per cent of oxygen, but an acety-
lene lamp is not extinguished until the oxygen is reduced to about 12
per cent. When 3 to 4 per cent of the dioxide is present most people
begin to feel its effects in headaches or other derangements, and real
distress may be caused by 5 to 6 per cent of the gas in the air. Where
carbon dioxide is present owing to exhalation of animals it is not only
this gas which causes the trouble but also the deficiency in the oxy-
gen which has been removed by breathing.

FIG. ioo. Shaft bottom of Jerome Shaft No. 2. Hillman Coal and Coke Co.
(By courtesy of the Hillman Coal and Coke Co.)

Carbon monoxide. Carbon monoxide (CO) is an odorless, color-
less gas with a molecular weight of 28, a density of 14, and a specific
gravity 0.967. It is, therefore, slightly lighter than air. Its rate of
diffusion compared with air is 1.0149 an d its ignition point 650 C.
When mixed with air in any proportions it forms white damp. Un-
like carbon dioxide it is a deadly poison, the effects in some cases being
sudden, in other cases delayed. It requires only about T V of i per

CARBON MONOXIDE

293

cent of this gas in air to cause dizziness, headache, shortness of breath
or other effects, and T \ may be dangerous, while T \ of it is almost sure
to be fatal. The gas attacks the haemoglobin of the blood and 60
to 70 per cent saturation of the blood is fatal. It usually takes from
5 to 6 hours to free the blood after a serious case of poisoning. The
effect on the blood is to turn it a pink color. The best treatment is to
remove the patient into pure air and apply heat to the body by wrap-
ping up in warm blankets or applying hot-water bottles. In serious
cases of poisoning it may be necessary to use pure oxygen mixed with
10 per cent CC>2. To test mine gas for the presence of CO a small
animal such as a mouse or canary bird is used, the latter being the best
indicator. Experiments by the United States Bureau of Mines 1 have
shown that in air containing carbon monoxide canaries and mice be-
haved as follows:

TABLE SHOWING THE EFFECT OF CARBON MONOXIDE
ON ANIMALS

Percentage
in air

Canaries

Mice

Chickens

Dogs

Guinea pigs

O.IO

No. tested 8;
i affected in
12 min., 2
slightly af-
fected in 4
hours.

No. tested 7;
i distressed
in 30 min., 6
showed no
distress in 2\
hours.

No. tested i;
no effect in
2\ hours.

0.15

No. tested 4;
affected in 5
to 30 min.

No. tested i;
affected in
45 min.

No. tested i;
no distress in
45 min.

O.2O

No. tested 12;
i distressed
in 35 min., n
in 2 to 6 min.

No. tested 6;
i distressed
in 40 min., 5
in 6 to 1 2 min.

No. tested 4;
distressed in
10 to 45 min.

No. tested i;
slightly
distressed
in 5 min.

o-35

No. tested 2;
i distressed
in i min., i
in 2 min.

No. tested 2;
i distressed
in 2 min., i
in 3 min.

No. tested i;
distressed
in 4 to 9
min.

0.50

No. tested 8;
distressed
in 2 to 9
min.

It is evident that all animals of the same species are not affected to
the same degree. If an animal becomes accustomed to small amounts

1 Burrell, G. A., Seibert, F. M., and Robertson, I. W., Effects of carbon monoxide on
small animals. U. S. Bur. of Mines, Tech. Paper 62, 1914.

294 MINING OF COAL

of the gas it is more resistant to future attacks. Small animals are
more readily affected than human beings but not in proportion to
their weight. The flame of a safety lamp is not affected by less than
i J per cent of this gas and about 2 per cent is necessary to show a cap.
This cap is similar to that of marsh gas. An instrument known as
the M-S-A Carbon Monoxide Detector has recently been put on the
market; it is very sensitive to this gas and is supposed to indicate
within ten seconds any percentage of the gas from 0.05 to i. Car-
bon monoxide is explosive when mixed with air in proportions of about
I 5-5 to 75 per cent, but the presence of carbon dioxide and marsh
gas affects these limits by respectively raising and lowering them.

Carbon monoxide is formed by incomplete combustion of carbon
in a fire when the oxygen supply is deficient, by the explosion of some
types of blasting powder such as those deficient in saltpetre and by
the partial oxidation of organic material. The first process is the
most important producer of the gas.

Methane. This gas is also known as marsh gas (CH 4 ), and when
mixed with air it forms fire damp. Its molecular weight is 16 and its
specific gravity 0.53. It is thus much lighter than air. It is non-
poisonous, tasteless, odorless and colorless. It will not support com-
bustion but it will burn with oxygen, producing water and carbon
dioxide, when the proportions of the gas vary from i volume of gas
to between 3.5 and 30 volumes of air, the greatest explosive intensity
being reached when the proportions are i volume of methane to 9.5
volumes of air. The cap produced on the flame of a safety lamp is
the means usually employed in detecting the presence of the gas and
the following table shows how the cap develops with the varying per-
centages of the gas present in the air :

Percentage of methane Height of cap and flame

i Base of cap forming

1 2 iinch

2 f to 2 inch

25 | inch and slightly luminous top

2 f finch

3 i j inches

35 15 to if inches

3f Up in gauze

An increase in moisture lowers the explosibility of fire damp and a
mixture of i part of carbon dioxide with 7 parts of an explosive mixture

SAFETY LAMPS 295

of air and marsh gas makes it non-explosive, or i part of nitrogen to
6 parts of a similar mixture produces the same result.

Marsh gas is abundant in some mines but almost entirely absent
in others. It is given off by the coal and it results from the alter-
ation of the vegetal matter in forming coal as indicated in a general
way in the following equation:

C 57 H 56 10 - (3H 2 + C0 2 + 2CH 4 ) = C^A

Lignite Bituminous coal

As previously mentioned, one mine in the anthracite region of Penn-
sylvania has produced as much as 2400 cubic feet of methane per
minute. (For further notes see discussion of gases under the Chemi-
cal Properties of Coal, Chapter II.)

Hydrogen Sulphide. Hydrogen sulphide, or sulphuretted hy-
drogen (H 2 S) occurs in mines in small amounts and when it is mixed
with air the mixture is known as stink damp or stone damp since it
has a very strong and disagreeable odor. It results in very small
amounts from blasting, especially where black powder is used and
it is also set free through the decay of organic matter. The odor of
rotten eggs is largely due to the presence of this gas. It may also
be generated by the action of acids on sulphur compounds. The gas
will not support combustion but it burns in air with a pale blue flame,
the temperature of ignition being 333.3 C. or at red heat. When
mixed with one-half times its own volume of air it burns with ex-
plosive force and with 7 volumes of air it explodes violently. It
produces headache, nausea and the loss of the sense of smell, and if
inhaled in sufficient quantities results are fatal. The amount neces-
sary to produce death in a human being is about i part by volume to
200 parts of air. Canary birds are sensitive to about .05 per cent in air.
Treatment consists in removal to a plentiful supply of fresh air, and in
severe cases a little chlorine gas may be administered to aid recovery.

Hydrogen. This gas may be formed in small amounts in mines as
a result of incomplete combustion in mine fires or in explosions, but
it seldom occurs in noticeable quantities. Other rarer gases, including
some of the paraffin series, occur in very small quantities in mines.

Safety Lamps

Various methods have been devised for the lighting of mines, from
the torch and the flint mill which generated sparks by contact of a

296 MINING OF COAL

steel wheel with a piece of flint, to the high candle power electric light
of the present day. In gaseous mines it is necessary to have a closed
light and this gave rise to the safety lamp which is now found in such
great variety. The structure of the safety lamp is based on the prin-
ciple of a protecting envelope through which air will pass but which
will prevent the gases outside of the lamp from becoming heated to
the temperature of ignition. The first safety lamp was invented by
Clanney in 1813 and air was forced into it through a water seal by
means of a bellows. The Davy safety lamp was invented by Sir
William Davy two years later and had a wire gauze around the flame
to conduct the heat away so that the gases outside of the lamp would
not take fire. Credit is also due to George Stephenson for discovering
the principle of the bonnet 'the same year. The modern lamps are
safely locked so that a miner cannot unlock them in the mine but must
take them to a safe place to be unlocked by a key or an electrical
device. Most of them have a self-lighting device inside which in-
sures greater safety to the men. Oil is the fuel mostly used. The
light is much better in the modern lamp than in the older types since
it has a glass envelope or chimney and the air enters near the base of
the lamp.

The electric cap lamp has made its appearance in the mines during
the last seven years and it gives promise of being very largely used
because of its greater convenience and its efficiency in producing light. 1
It has one serious objection to the miner used to the other safety lamps,
and that is the fact that it does not indicate the presence of harmful
gases.

For open lights in non-gaseous mines acetylene generated from
calcium carbide in contact with water produces a very efficient light
and acetylene lights are very commonly used.

Mine Ventilation

Since a coal mine is certain to contain more or less foul air it is
essential that it be well ventilated. There are two means of ven-
tilating a mine: by a furnace and by a fan. A furnace may be used
in the smaller mines which are not gaseous. It is built of brick at
the foot of a shaft on the main airway, so as to create a strong upward

1 Clark, H. H., Permissible electric lamps for mines. U. S. Bur. of Mines. Tech.
Paper 75, 1914.

MINE VENTILATION 297

draft by convection currents generated by a fire which is kept burning
all the time men are at work in the mine.

Mine fans are of many types. They may be constructed as the disc
fan where the blades are arranged as they are on a windmill or as the
centrifugal type in which the blades are normal to the plane of revo-
lution. The fans are usually run so that they propel the air through
the airways and to all the working places in the mine, but in some
cases the fan may be run as an exhaust fan. It is considered neces-
sary to so ventilate a mine that every man may have a minimum of
150 cubic feet of air per minute if the mine be non-gaseous and 200
cubic feet if it be gaseous. The velocity of the current of air in the
mine workings is measured by an anemometer and the pressure by a
water gage. If the anemometer reading were 1800 feet in three
minutes and the size of the airway 6 feet by 10 feet the volume of air

passing through would be found in the following way: 6 x 10 X -

= 36,000 cubic feet per minute. Fans are as much as 35 feet in diam-
eter and they are capable of delivering from a few thousand up to over
400,000 cubic feet of air per minute, depending upon the size and type
of the fan, the rate at which it is run, and the mine resistance.

In ventilating a mine the foul air and explosive gases are driven out,
but the fresh supply of oxygen tends to oxidize the coal and to set
methane free, sometimes at a rapid rate. The air entering the mine
becomes warmed and the presence of air with the increased tempera-
ture aids the absorption of moisture which is carried out with the air
current, leaving the mine dry and in some cases dusty. The fine coal
dust becomes distributed through the air and acts much the same
as an explosive gas when ignited. 1 It has been shown that the dust
is capable of producing tremendous explosions and it is particularly
dangerous when mixed with gas as this increases the possibility
of igniting the dust by lamps or blasts. The discovery of the ready
explosibility of coal dust has aided greatly in avoiding many bad ac-
cidents. The danger of explosions may be greatly lessened by
sprinkling the mine, and taking other precautions against trouble
such as regulating the use of certain explosives, like black powder
which generates a long flame on firing. There are certain explosives

1 Rice, G. S., and others, Explosibility of coal dust. U. S. Geol. Survey, Bull. 20, 1911.

298 MINING OF COAL

designated as permissible explosives 1 for coal mines and the use of
these has aided in reducing accidents although they are not always
the most suitable from the practical standpoint for producing the best
type of coal for the market. Great strides have been made in recent
years in the direction of greater protection for life and property in coal
mining and the percentage of accidents has been greatly reduced.
Mining has become a relatively safe occupation.

Mine Fires

Mine fires are one of the great causes of trouble in coal mines and
they start by lamps firing gas, timbers or coal, or from blasts or spon-
taneous combustion. If they are taken in their incipient stages they
can as a rule be put out although the safest practice is to take all
precautions against letting them get started. When small they may
be put out with water or a chemical extinguisher but when once well
started they must be flooded or smothered out. In some cases it
may be necessary to flood the whole mine, while in others dams of con-
crete, masonry or wood may be built and the spaces behind them
flooded. In smothering a fire the mine shaft may have to be sealed
up or a portion of the mine may be walled off and sealed so tightly
that the fire dies out for want of oxygen. The sealing is done by walls
of rock and clay, masonry or concrete. Sometimes a wooden wall is
built, and clay, sand or other suitable material is filled in behind it.
The waste or " slush " from a breaker or washery may in some cases
be turned into the mine to seal up the fire. It is often extremely
difficult to seal the area so tightly that no oxygen can enter and
there are some fires which have burned for over half a century
baffling all attempts to extinguish them. When sealed the area may
retain its heat for years, and in some mines the fire which was sup-
posed to be dead has broken out as soon as air was admitted. Great
care must therefore be exercised in reopening a sealed mine or local
area in a mine.

In some cases fires have been extinguished by mining out the seam
around the fire, thus isolating it.

1 Howell, S. P., Permissible explosives tested prior to Mar. i, 1915. U. S. Bur. of
Mines, Tech. Paper 100, 1915.

CHAPTER XI
THE PREPARATION AND USES OF COAL

Introduction

A glance at the statistics of distribution of coal mined in the United
States shows the manner in which the coals of various ranks are di-
vided for consumption. 1 In 1917 the distribution of approximately
80 million tons of Pennsylvania anthracite was as follows: nearly 51
million tons were of domestic sizes; 18 million tons of steam sizes;
6 million tons were used by railroads and over 4 million tons exported.
For the same year about 366 million short tons of bituminous coal,
mined and distributed in this country, were divided as follows:

Used at mines for steam and heat 12,117,159 tons

" in manufacture of beehive coke 52,246,612

" in manufacture of by-product coke S^SQS^SQ

" in manufacture of coal gas ........ 4,959,697

" by electrical utilities 31,692,722

" for domestic purposes 57,104,000

" for industrial purposes 176,365,939

In addition to the coal included in these figures about 153 million tons
were used by the railroads and over 10 million tons were loaded at
seaports for bunker purposes. Approximately 23 million tons were
exported.

For industrial purposes and for the use of the railroads, the two
largest items of consumption, a great variety of coals and grades of
coal may be used. The same holds true for the electrical utilities,
mine consumption and to a certain degree for domestic purposes.
For certain types of industrial operations where special coals are
required as, for example, in smithing, there were 255,000 tons used.
For coking purposes certain limits may be placed on the grade and
ranks of coal used, as low sulphur coals and coking varieties must be
selected.

For domestic purposes the distinctions made lie more in the prep-
aration of the coal for use than in the rank or grade of the coals, since
all ranks from lignite to anthracite are extensively used and some
of the coals are of very low grade. For gas manufacture particular
types of fairly high volatile coals are best.

1 U. S. Geol. Survey, Mineral Resources of the United States, 1917.

299

3 oo

THE PREPARATION AND USES OF COAL

Preparation of Coal for Domestic Purposes

Anthracite. On account of its high heating, low smoke-producing
and long-burning qualities, and its freedom from dirt and dust,
anthracite has long been a favorite domestic fuel. The operation of
preparing it for market has become quite a highly developed me-
chanic art.

FIG. 101. Slate pickers in an anthracite breaker. (Photo by courtesy of R. P. Hutch-
inson of the Bethlehem Fabricators Inc.)

There are two main objects in view in breaking and separating
anthracite, one being that of getting it into uniform sizes so that it
will readily burn in a grate and the other that of cleaning the coal
by washing out the small particles of mineral matter and by removing
the larger fragments of slate by hand or with mechanical separators.
According to Sterling 1 the methods of preparation may be grouped
under three classes, as follows: (i) Dry preparation, used for
lump coal which comes from the mine dry and which readily

1 Sterling, Paul, The preparation of anthracite. Trans. Amer. Inst. Min. Eng., Vol.
42, p. 264, 1912. Also Peele's Handbook for Mining Engineers, p. 1842.

ANTHRACITE

301

separates from the waste rock; (2) Combination of dry and wet
preparation employed when the run-of-mine contains a high per-
centage of impurities, perhaps up to 55 per cent, but also consid-
erable lump coal which can be handled as in (i); (3) Wet prepara-
tion, when the run-of-mine is high in impurities and is discolored
with iron or clay. This type of coal occurs near the surface and in
disturbed zones in the mine.

The coal is taken from the mine mouth to the breaker in the mine
cars or by conveyors, depending upon the relative position of the pit
mouth and the top of the breaker. It is first passed over a sizing screen,
sometimes known as a bull shaker, which sorts the lump from the
smaller material, the former going to a picking table and the latter,
which is often called the mud-screen product, moving along to be
treated by the wet process, (Fig. 101). On the picking table pieces
of rock are removed by hand. If coal and rock adhere the lumps are
removed to a special table where they are broken by hand and the
rock sent to the rock pile.

The cleaned lump goes to a pocket for shipment as lump or to the
rolls to be broken, depending upon the demand for the different
sizes. The rolls, which are furnished with teeth, break the coal into
the sizes indicated by the following table:

TABLE SHOWING MARKET SIZES FOR ANTHRACITE AND
SCREEN OPENINGS IN INCHES

Size of coal

Punched plate

Woven wire

Round

Square

Over

Through

Over

Through

Over

Through ,

Lump

6^
4^
3*

ife

J P

'ei

2
I*

1 3

16
9
T 6

Ji'

3
4

If'

2
if

Steamboat

Broken

Egg. .

Stove

Chestnut

Pea

Buckwheat

Rice

Barley

Buckwheat No. 4

3 02

THE PREPARATION AND USES OF COAL

The percentages of each size allowable in the other sizes and the
percentage of slate and bone allowable in the various sizes is shown
in the following table:

TABLE OF STANDARDS OF PREPARATION IN PERCENTAGE

May contain

Broken

Egg

Stove

Nut

Pea

Buckwheat

Rice

Barley

Of slate

2-5

Of bone

Of next size

larger

Of next size

smaller

ISB

2 5

isR

After screening, the steamboat size is either sent to a pocket and
shipped or sent to other rolls and further crushed, according to the
condition of the market for various sizes. This process is continued
until the whole operation is complete except that certain portions of
the coal are put through the wet process to clean it if necessary. The
course followed is clearly outlined by Ashmead 1 in the accompanying
diagram, (Fig. 102).

The screens used in recent years are largely of the shaker type
rather than the oscillating or gyratory screens. The advantages of
the shaker type, according to Sterling, are: low first cost; ease with
which it may be repaired and maintained; good sizing of smaller
sizes; large capacity; ability to size material not over 150 pounds
in weight in going to the picking room. The revolving screen does
not vibrate the breaker as much as a shaker screen and it performs
exact screening and sizing. It has smaller capacity, however, and
requires more space than shaking screens of the same capacity. Only
about one-eighth of the surface is in contact with the coal at one
time. The first cost and maintenance are high.

There have been some recent developments in the use of jigs, es-
pecially of the plunger type, for separating the slate from the coal,
and mechanical pickers are used a great deal for the same purpose
in dry preparation. Where hand picking is done the moving table

1 Ashmead, D. C., Modernized breaker with hand pickers, spirals, jigs and concen-
trators. Coal Age, Vol. 18, p. 585, 1920.

ANTHRACITE

303

THE PREPARATION AND USES OF COAL

is found to be an advantage. In the automatic mechanical pickers
the moving table is so arranged as to give it a pitch in two directions,
first transverse to the table, and second along the center line. This
requires the moving material to travel up hill and the coal is separ-
ated from the rock, owing to difference in specific gravity and friction

FIG. 103. Cross-section of Alliance Breaker, showing loading method. (After Ash-
mead: Reproduced by courtesy of Coal Age.)

of the coal and slate on the table. The rock discharges at one point
and the coal at another. With the increased efficiency of the cleaning
equipment in the modern breakers it is now possible to save a much
larger percentage of the coal than formerly and some of the culm
banks can be reworked. Several large Pennsylvania anthracite
companies have quite recently installed tables of the Deister-Over-
strom type for washing the barley and smaller sizes of coal. There

BITUMINOUS COAL

305

seems to be a good future in the Anthracite region for the application
of some of the devices so long used for ores, and adopted in some of
the western fields for coal washing and separation.

Bituminous coal. It is becoming more and more a custom to
wash and size bituminous and semibituminous coal for domestic pur-
poses. A cleaner coal and a coal which will burn better and stand
storage better is produced in this way, and mining operations are
aided because some labor in sorting coal and rock underground is
saved. At many mines simple bar screens are used while at others
modern shaker screens have been adopted. The coal is sorted into
various sizes somewhat like anthracite but on a less perfectly devel-
oped plan. The state of Illinois has probably been the most advanced
of the states of the Union in the systematic preparation of bituminous
coal, and now only about 20 per cent of her output is sold as run-of-
mine, the remainder being treated before shipment is made. 1 This
remarkable development in washing and sizing operations in Illinois
is partly due, however, to the fact that very little of the coal in the
state is of coking quality. This is a type which does not need sizing for
market, although it is customary to wash a great deal of coking coal to
reduce the sulphur content. At mines where the coal is only passed
over shaking screens and then sold, four sizes are commonly made;
these are known by the following names:

Name

Size in inches

Per cent of total output

Lump

Over 6

T (J

Eee

Over 3^ through 6

No. i nut

Over if through 3^

No. 2 nut

Over i through if

II?

No. 3 nut

Over f through i

No. 4 nut

Over j through f

No. 5 nut

Through j

The sizes for these different types vary somewhat in different fields.
In some areas the lump sizes run through 8 grades of lump, from 8-
inch lump to ij-inch lump and on down through chunk, egg, nut, pea
and screenings. At some mines mechanical pickers, as well as men
and boys, are employed and some companies wash the coal in addition

1 Andros, S. O., Coal mining in Illinois. Illinois Coal Mining Investigations. Bull.
13, p. 202. Urbana, 1914.

3 6

THE PREPARATION AND USES OF COAL

to screening it. Washing tends to remove clay, slate and iron pyrite
and this is quite an advantage for high sulphur coals for coking.
An elaborate washery was put into operation at the United States
Fuel Company's mine at Benton, Franklin County, Illinois in the
fall of 1918. l It has been the hope of mining men that the greater
part of the sulphur could be removed from coal by washing out the
pyrite. Unfortunately, as previously pointed out in this text, it is
impossible to wash out the sulphur in organic compounds, or the
finely divided pyrite which is almost always present.

FIG. 104. The Loree Breaker. (Photo by courtesy of R. P.
Hutchinson, Bethlehem Fabricators, Inc.)

Storage

The storing of coal is a very important item in many industries.
If it is not stored at times when it is plentiful and transportation
facilities are good, plants may be tied up owing to break-downs in
traffic or mining operations, resulting from storms, strikes or other
causes. Another advantage in storing coal is that it distributes the
demand more uniformly over the whole year and the peak load does

1 Campbell, J. R., Mechanical separation of sulphur minerals from coal. Trans. Amer.
Inst. Min. and Met. Eng., Vol. LXIII, p. 683, 1920. Also, Frazer, Thomas and Yancey,
H. J., Some factors that affect the washability of a coal, p. 768.

SPONTANEOUS COMBUSTION 307

not always fall in the winter when most coal is likely to be needed.
According to Stock the coal should be stored as near the place where
it will be used as possible, although it is practical to store at the mines
temporarily when the car supply is short. The main objections to
storage of coal in large amounts are the breakage, the cost of re-
handling, danger of fire from spontaneous combustion or other causes,
the deterioration from weathering, the difficulty in securing adequate
storage facilities in large cities where the coal may be stored near
the plant in which it is to be used, and the possibility of a sudden
and considerable drop in price. 1

Spontaneous combustion. The cause of spontaneous combustion
is heating of the coal by oxidation and other agencies. Oxidation is
continually going on in coal exposed to the air and there is a general
impression that sulphur in the form of pyrite is responsible for much
of the trouble. This is not the real cause although it may aid the
chemical processes producing the heat. Sulphuric acid is developed
to a certain extent in the weathering of iron pyrite and since it is such
a strong oxidizing agent and generates so much heat on coming in
contact with water the presence of pyrite will naturally have an effect
on chemical action. It should be borne in mind, however, that the
condition in which the pyrite occurs in the coal, whether finely divided,
or coarsely crystallized, will have some influence on its rate of weather-
ing and it is found that the rate varies greatly. Specimens of pyrite
in a collection in a laboratory show great differences in the rate of
alteration. Some will break down in the course of a few years while
others will remain perfectly bright for an indefinite period.

In a recent paper some English writers 2 have claimed that fusain,
(mother-of-coal or mineral charcoal) probably aids spontaneous com-
bustion owing to the ease with which it crumbles to powder and takes
fire. It smoulders in many cases without any evidence of flame.
These writers have also found, as previously mentioned in this work,
that mineral charcoal contains a higher percentage of ash and fixed
carbon than the coal in which it occurs and that it is deleterious to the
production of good coke. It seems possible to the writer, in view of

1 Norris, R. V., The storage of anthracite. Trans. Amer. Inst. Min. Eng., Vol. XLII,
p. 314, 1912. (Full discussion of systems of storage and handling.)

2 Sinnatt, F. S., Stern, H., and Bayley, F., Does fusain cause mine and bin fires, spoil
coke and aid explosions? Coal Age. Vol. 18, p. 384, 1920.

308 THE PREPARATION AND USES OF COAL

the great absorptive quality of wood charcoal, that mineral charcoal
may have the power of occluding within its walls more gases than or-
dinary coal, and the presence of these gases would influence spon-
taneous combustion. This would be a very interesting field for in-
vestigation.

An investigation of the causes of spontaneous combustion with
special reference to Illinois coals was carried out by Parr and Kress-
mann 1 and their conclusions were that the following factors entered
into a consideration of the subject: (i) kind of coal with regard to
its volatile matter; (2) purity of the coal; (3) presence of pyrite and
other sulphur compounds; (4) temperature of the coal; (5) size of
the fragments; (6) presence of occluded gases; (7) presence of mois-
ture; (8) accessibility of oxygen; (9) pressure on the coal.

Regarding the kind of coal, it is found that those high, or fairly high,
in volatile matter such as lignites, subbituminous, bituminous and
semibituminous coal are the only ones which are likely to take fire.
The anthracitic coals have too high an ignition temperature and they
weather too slowly to take fire readily. According to Fayol lignite
as fine dust takes fire at 150 C., gas coal at 200 C., coke at 250 C.
and anthracite at 300 C. or above. He also found that coal absorbed
oxygen about twice as fast as did pyrite.

The pure coals seem to oxidize more rapidly than those with more
foreign matter. The effect of pyrite has already been described above.
The size of the coal is an important factor as fine coal is a much more
rapid absorbent of oxygen than lump and is dangerous in storage.

Occluded gases of an inflammable type, such as methane, no doubt
favor spontaneous combustion, but to what extent is unknown.

Moisture under certain conditions aids the process since it influ-
ences the oxidation of pyrite and coal. Accessibility of oxygen is
without question an important factor.

Pressure is believed to be an important factor in aiding the devel-
opment of heat in coal, but to what extent and in what manner is not
very fully understood.

Some of the remedies suggested for spontaneous combustion are:
storage under water to eliminate oxidation; exclusion of fine coal by
screening, or its regular distribution throughout the pile; keeping

1 Parr, S. W., and Kressmann, F. W., The spontaneous combustion of coal, Illinois
Experiment Station, Bull. 46, 1910.

BRIQUETTING 309

the piles low, only a few feet hign; keeping the coal away from ex-
ternal sources of heat such as boilers, pipes or the sun's rays; keeping
it dry unless completely submerged; and elimination of high sulphur
coals.

The deterioration of coal in storage. From the researches of
David White, previously mentioned, it is shown that oxygen in coal
is practically equivalent to ash in its anti-calorific properties. The
oxidation of coal therefore decreases its heating value. Regarding
the deterioration in storage Parr 1 concludes that very little loss is
suffered if the temperature is not allowed to rise above 180 F. as there
is no appreciable evolution of CO 2 below 200 F. The loss per pound
in heat value is due largely to an increase in weight per unit mass of
coal on account of the absorption of oxygen, and Parr claims that
the weathered coal gave just as satisfactory results in firing, if care
were taken in controlling the fire, as the unweathered coal. In an
earlier article Parr and Hamilton 2 present the following conclusions,
in addition to those previously set forth: Submerged coal does not
lose appreciably in heat value while outdoor exposure results in a loss
in heating value of from 2 to 10 per cent. In some cases the losses
appear to be complete at the end of five months. From the seventh
to the ninth month the loss is not appreciable. Similar results were
obtained by Porter and Ovitz 3 in experiments on Sheridan, Wyoming
coal. They found that this coal lost 3 to 5.5 per cent of its heating
value in about three years in storage, 70 to 80 per cent of the loss oc-
curring within the first nine months. They also found that storage
in air-tight bottom bins had a distinct advantage over covering the
surface of the coal. The slacking of the coal is one of the important
factors in weathering as it tends to destroy its firing qualities.

Briquetting 4

The process of briquetting coal has developed considerably in re-
cent years. It is applied to fuels which are dusty, such as peat, lig-

1 Parr, S. W., Effects of storage upon the properties of coal. University of Illinois,
Bull. No. 39, Vol. XIV, 1917.

2 Parr, S. W., and Hamilton, N. D., The weathering of coal. University of Illinois,
Bull. No. 33, 1907.

3 Porter, H. C., and Ovitz, F. K., Deterioration in the heating value of coal during
storage. U. S. Bur. of Mines, Bull. 136, 1917.

4 Franke, G., A handbook of briquetting. Translated by F. Lantsberry, Charles
Griffin and J. B. Lippincott, 1917.

310 THE PREPARATION AND USES OF COAL

nite, fine slack, and culm. It consists of compressing the powdered
fuel into briquets or little bricks, using pitch as a bond to hold the
particles together. The pressing is done at rather high temperatures.

In recent years much material from the culm banks of the anthra-
cite region of Pennsylvania has been recovered, washed, dried, and
briquetted. Many of the old culm piles contain the coal which is now
sold as barley and buckwheat sizes. According to Dorrance, 1 at the
Lehigh Coal and Navigation Company's plant the culm is loaded into
gondolas of ioo,ooo-pound capacity and taken to a track hopper at
the briquetting plant. It is elevated to the drying plant and passed
through Vulcan rotary kiln driers which are heated by gases from the
furnace. It is screened on vibrating screens of Newago type, the
material passing through the finest screen going to the refuse conveyor.
The refuse from this and later screenings is sent to the mines at Sum-
mit Hill for slushing the mine fire burning there. Commercially-
sized coal separated is sent to the drier building for feeding the fur-
naces. The material from the screens is sent to Damon air separators
and the coal retained from them is sent to the bins and from there to
the mixing-house. Solid coal-tar pitch is used as a binder and it is
fed into rolls and cracked to " pea " and " dust" sizes. This is then
elevated to the pitch-measuring apparatus which feeds the right pro-
portion of pitch to a squirrel-cage pulverizer which in turn feeds it
into a screw conveyor with a measured amount of culm material.
These materials then pass to the briquetting-house and are sent
through the mixers to the presses. In the mixers the material is
heated with superheated steam to about 400 then cooled by a cooling
fan and pressed into briquets. Briquets are used by the railroads and
industrial concerns, while the little balls known as boulets are sold
for domestic use since the larger size does not seem to burn as well
in domestic heaters as the smaller balls.

Experiments have shown that a great number of binders may be
used for briquetting, but some of them cost a prohibitive sum. 2 The
nearness to the source of supply influences to quite a large extent
the choice of the type of binder. The following binders have proven
satisfactory and they are available in many localities: (i) Asphalt,

1 Dorrance, Charles, Jr., Anthracite culm briquets. Trans. Amer. Inst. Min. Eng.,
Vol. XLII, p. 365, 1912.

2 Mills, James E., Binders for coal briquets. U. S. Bur. of Mines, Bull. No. 24, 1911.

PRODUCER GAS

the heavy residuum from petroleum, costing about 45 to 60 cents per
ton of briquets and used in proportion of 4 in 100. (2) Water-gas
tar pitch costing 50 to 60 cents; 5 or 6 per cent is used. (3) Coal-
tar pitch; 6.5 to 8 per cent is used per ton and the cost per ton of
briquets runs 65 to 90 cents for binder. Other substances which
might be used are starch, sulphite and magnesia.

The results of the tests made on briquets by the Bureau of Mines 1
indicate that there is considerable difficulty in burning them in do-
mestic heaters where low temperatures prevail so much of the time,
as the binder either tends to produce a deposit on the interior walls
of the furnace and the pipes which clogs them, or it burns off too
rapidly when the temperature rises quickly. The briquets ignite
readily unless an inorganic binder is used or there is too much im-
purity in the slack from which they are made, and they produce a
large amount of smoke if not properly fired. Their relative efficiency
is high, they are clean and they weather very well. It is concluded,
however, that there is no justification for briquetting lump coal
and the main advantage in the process lies in consolidating coal which
is in too fine a condition or is dusty. Lignite and fine coal, which
does not coke may be profitably briquetted in many cases. Coking
coals are more easily handled without briquetting than non-coking
types since they are not readily lost by running through the grates.
The average cost of briquetting a ton of fuel has been placed at about
$1.00 to $1.80. Recent developments in the briquetting of partially
devolatilized coal, or carbo-coal, indicate that there is probably a more
promising future along that line than in the briquetting of the raw
fuel.

Coals Used in Gas Manufacture

Producer gas. Coals which are used in gas manufacture may
vary greatly in quality and it is difficult to fix limits as to their prop-
erties. Fuels from peat to anthracite have been used for the manu-
facture of producer gas, which is coal gas diluted with air and often
mixed with water-gas. They should, however, be comparatively low
in sulphur and ash and the fusibility of the ash is an important fac-
tor. It should not be low. The size of the coal also has an impor-

1 Wright, C. L., Fuel briquetting investigations. U. S. Bur. of Mines, Bull. 58, p. 191,

312 THE PREPARATION AND USES OF COAL

tant bearing as coarse run-of-mine is not good material. Egg and nut
sizes are desirable and screenings may be used. 1

Illuminating gas. For illuminating gas a coal must be high in
volatile matter so as to yield per short ton at least 10,000 cubic feet
of gas at 60 F. and 30 inches mercury pressure, and the gas should
test 1 6 to 1 8 standard candle power. Cannel coal has long been
recognized as probably the most desirable coal for this purpose.
The quality of the volatile constituents is important as well as the
quantity. The coal should also yield a good proportion of coke.
The sulphur must be low, not above ij and preferably below i per
cent, although coals have been used in some cases which run up to
about 2 per cent. The sulphur unites with hydrogen to produce
hydrogen sulphide H 2 S and with carbon to produce carbon disul-
phide (082). The former is an evil-smelling, poisonous gas and the
latter under certain conditions has a horrible odor. Both of these
gases burn to sulphur dioxide (802) and this gas is not only suffo-
cating and objectionable to man but it aids in tarnishing metal house-
furnishings. The sulphur gases can be removed from the illumin-
ating gas at a rather high and in many cases prohibitive cost. 2

The following figures indicate the general chemical composition of
coals which have been used and are well adapted for gas making :

Cannel Bituminous gas coal

Moisture i . 30- 4 . 50 per cent i . oo- 4 . oo per cent

Volatile matter 30.00-39.00 " 28.00-37.00 "

Fixed carbon 50.00-60.00 " 54.00-61.00 "

Ash 2.20-6.00 " 3.50-10.00 "

Sulphur 0.50-1.05 " 0.80-1.32 "

B.t.u 13,000-14,500 13,200-14,600

Water gas. Water gas is a commercial gas consisting very largely
of carbon monoxide and hydrogen and it is made by dissociating
steam into hydrogen and oxygen, thus permitting the latter to unite
with carbon to form carbon monoxide (CO). Anthracite and coke
have been most generally used for this purpose but non-coking bitu-
minous coals might also be used.

1 Brooks, G. S., and Nitchie, C. C., Gas producer practice in western zinc plants.
Trans. Amer. Inst. Min. and Met. Eng., Vol. LXIII, p. 846, 1920.

2 Odell, W. W., and Dunkley, W. A., Removal of sulphur from illuminating gas.
Trans. Amer. Inst. Min. and Met. Eng., Vol. LIII, p. 660, 1920.

POWDERED FUEL 313

Smithing Coals

No very definite limits have been fixed for the quality of smithing
coals. Semibituminous or " smokeless " coals have been generally
used although anthracite and semianthracite coal have also been
used. Some of the requirements for a first-class coal of this type are
low sulphur, less than i per cent; high calorific value; low ash; and
sufficient coking quality to seal over and retain the fire when articles
are not being inserted or withdrawn.

Coals for Cement and Tile Burning

For a cement-burning coal the requirements are a high calorific
value, 12,000 B.t.u. and upward, and a high volatile content. For
burning brick and pottery, coals of high volatile content and non-
coking qualities are desirable.

For burning porcelain and the finer grades of ceramic materials
low sulphur is essential and low ash desirable. According to Par-
melee 1 the English pottery practice requires a coal which comes near
the following figures: Total sulphur, 1.20 per cent; sulphur in ash
o.i i per cent; and volatile sulphur 1.09 per cent. The practice in
America is about as follows:

For Sanitary ware: Maximum i.o per cent; 0.5 per cent desirable.

For Sewer pipe: As high as 3.10 per cent has been used but 1.2 per
cent should be the maximum and i.i per cent is about present run.

Terra Cotta: i.o per cent is approximate and 0.5 per cent is basis
of contract.

Pottery: i.o per cent contract basis and 1.5 per cent probable
content.

Enameled brick: 1.3 per cent maximum.

Powdered Fuel

Powdered fuel must be ground exceedingly fine and then be blown
into the furnaces with a supply of air adequate to completely con-
sume it. For ordinary steam purposes the sulphur and a reasonable
amount of ash do not greatly affect the qualifications, but for use in
the steel plants the sulphur and ash must be low. The same rules
should govern the proportions of sulphur in such fuel as in coke. The

1 Parmelee, C. W., Effect of sulphur in coal used in ceramic industries. Trans. Amer.
Inst. Min. and Met. Eng v Vol. LXIII, p. 727, 1920.

314 THE PREPARATION AND USES OF COAL

volatile matter should be over 30 per cent and the greater the pro-
portion of combustible gas in the volatile matter the better the quality,
other things being equal.

There is an interesting new development in the use of coal as a
colloidal fuel. 1 The use of this type of fuel is largely in the experi-
mental stage but there may be a large future for it. The colloidal
fuel in which coal has been concerned is very finely powdered coal
suspended in fuel oil. Several types of coal have been used and the
calorific power developed has been high. There seems to be a pos-
sibility of not only suspending the fine coal in the liquid as a mechani-
cal mixture but also of dissolving certain parts of it so that it actually
goes into a liquid condition.

Steam Coals

Coals used in the production of steam include especially those
used on ships, in locomotives and under stationary boilers and they
embrace a wide range in ranks and grades. The ideal steaming coal
is one combining high calorific power with small smoke- and clinker-
producing, as well as fairly long-burning qualities. It should also be
sufficiently high in volatile matter to permit a rapid response to
stimulated firing, as a fireman on a locomotive, for example, may
need a fire which responds rather quickly when heavy grades are
approached. The coal must also be capable of standing storage,
especially when employed for bunkering purposes. The presence
of sulphur will influence its qualities for storing as well as the clink-
ering of the ash since sulphur, especially in the form of mineral sul-
phides, seems to show a marked influence in lowering the temperature
of fusion of the ash if present in quantities over about 2 per cent.
The character of the ash and the methods of firing will also influence
the results to a marked degree. The iron of the pyrite unites with
other elements and produces more fusible compounds. The sulphur
compounds also break up and form new compounds some of which
corrode the furnaces.

Semibituminous, or so-called " smokeless," coal has long been rec-
ognized in America and abroad as the finest type of steam coal.

1 Sheppard, S. E., Colloidal fuels, their preparation and properties. Jour, of Ind.
and Eng. Chem. Vol. 13, p. 37, 1921.

COKE

It has the highest calorific value of any coal and it contains sufficient
volatile matter to make it ignite a little more readily than anthracite.

Some of the best steam coals in America are the semibituminous
coals of Virginia, West Virginia, Maryland, Central Pennsylvania,
Arkansas, and Alberta, Canada. The steam coals of South Wales
have long been famous.

Analyses showing the limits in composition of some of the well-
known types of semibituminous coals in the United States are as
follows i 1

Arkansas

Maryland

Pennsylvania

West Virginia

Moisture
Volatile matter
Fixed carbon. . . .
Ash

0.85- 3.50
II .40-16.60
72.00-77.00
7 4OI2 OO

0.38- 3.40
15.40-27.00
57.20-76.60
4 20 18 so

0.57- 4.50
15 .80-27.20
64.30-78.00
2 4012 2O

0.30- 3.40
13 .IO-22.OO
71.90-79.00
2 OO I I 2O

Sulphur
B.t.u

1.30- 2.8o
13,20014,650

0.80- 4.70

12,76014,900

0.50- 2.IO
1 3,400 IA, 6 SO

0.50- 2.50
14. OOO 14. Q2O

An analysis of high-grade Pocahontas coal would be illustrated by
the following figures: Moisture, 1.31; Volatile matter, 16.30; Fixed
carbon, 77.06; Ash, 5.33; Sulphur, 0.67; and B.t.u. 14,746.

Coking

The coking of coals for the purpose of securing metallurgical coke
is a process which has long been in vogue and it has attained a place
of great importance in our industrial operations. There are, however,
some new phases of this process which bid fair to become of much
more widespread interest than that of simply securing metallurgical
coke. They are the saving of the volatile products from the coal and
the production of solid fuels which will be better suited than coal for
domestic use and for some industrial purposes.

Coke. Coke is the hard residue obtained from heating coals in
the absence of air. It has a dull to submetallic luster, is dark
gray to silvery gray in color and is very porous, or vesicular. There
is sometimes a great variation in the strength of coke made from the
same coal seam. Some of it will support the largest blast furnace

1 Analyses from the Coal Catalog, Zern, E. N., Editor, Keystone Publishing Co.,
Pittsburgh, 1918. This work contains analyses of practically all coal seams in the
country.

3i6 THE PREPARATION AND USES OF COAL

charges while other portions will not. The percentage of coke which
may be derived from coal varies from about 50 to 80 per cent, but a
profitable coking coal should yield on the average at least from 65
to 70 per cent coke.

Coking coals. The question of what physical and chemical
properties determine the quality of a coking or caking coal has not
been fully decided. It is known that certain portions of a coking
coal are soluble in such solvents as aniline, phenol, or pyridine, and
that these soluble constituents constitute the better coking ingredients.
As previously stated in the discussion on coking coal it has been
found by Pishel that coking coals tend to adhere to the sides of an
agate mortar when rubbed with a pestle while non-coking coals do not.
White also shows that there is some relation between the oxygen and

hydrogen ratio and the coking quality. When > 58 the coal

TT TT

generally cokes; when > 55 < 58 the coal may coke; when -- >

5 < 55 the coal is not likely to coke satisfactorily. Exceptions
must be made for weathered coals. A test which is often used, es-
pecially in Europe, to determine the coking qualities of a coal con-
sists in mixing the powdered coal with sand and heating the mixture.
The coking quality is judged from the ability of the coal to cause the
and grains to stick together in a coherent mass, and the greater the
amount of sand the coal can cement the better its coking qualities.
The relative qualities of the various coals are fixed by a scale made
for that purpose. All coals leave a residue but in many cases it is
powdery and incoherent and of no value unless it is briquetted. It
is assumed that a good coking coal should run over 30 per cent vola-
tile matter and have not more than i J per cent sulphur and 0.02 per
cent phosphorous.

The requirements of the American Society for Testing Materials,
for standard foundry coke are that the dry coke shall not exceed the
following limits in chemical composition :

Volatile matter not over 2 . o per cent

Fixed carbon not under 86.0 "

Ash not over 12.0 "

Sulphur not over i . o "

Sulphur in coke. Owing to the fact that the mineral constit-
uents in the coal mostly enter the coke with the ash some of the sulphur

SULPHUR IN COKE 317

is carried into the coke. The statement is frequently made that
approximately one-half of the sulphur of the coal is driven off and the
other half remains in the coke. This assumption has been largely
verified by the recent work of Powell 1 although some factors not always
considered must be taken into consideration in dealing with this
subject. Sulphur in the coal may be in three forms: mineral sul-
phides, as pyrite and related minerals; organic sulphur, in some un-
determined form; and sulphates, in small amounts. The organic
type occurs in quantities ranging from 0.5 to 2.0 per cent and the
quantity is nearly uniform for a seam or locality. Apparently this
uniformity is due to the nature of the plants which grew in that
locality and to the bacteriological and other conditions existing at
that time. Pure pyrite is completely decomposed at 1000 C. and
the resulting products are ferrous sulphide and free sulphur, the
latter uniting with hydrogen if this element be available to form hydro-
gen sulphide. A negligible amount of the sulphur remains in the
ferrous sulphide in the form of a solid solution known as pyrrhotite,
or magnetic sulphide of iron. The sulphur is thus practically equally
divided between the volatile and residual constituents. From his
tests on the carbonization of coals Powell concludes as follows: (i)
At 300 C. decomposition of the pyrite begins with the formation of
pyrrhotite and hydrogen sulphide. The reaction is complete at 600 C.
and reaches its maximum between 400 and 500 C. (2) At 600 C.
the reduction of sulphates to sulphides is complete. (3) Decomposi-
tion of J to J of the organic sulphur takes place to form hydrogen
sulphide. Most of this reaction occurs below 500 C. (4) A small
part of the organic sulphur decomposes to form volatile, organic
sulphur compounds most of which enter the tar. This reaction takes
place chiefly at the lower temperatures of the process. (5) A portion
of the pyrrhotite disappears and the sulphur apparently enters into
combination with carbon. This reaction is most active at 500 or
more. Between 400 and 500 C. the organic sulphur not accounted
for above undergoes decided changes and ceases to resemble the
original sulphur in the coal. It appears therefore that the percentage
of sulphur originally in the coal rather than the form of the sulphur
will be the prevailing factor to be considered. Some carbon bisul-

1 Powell, A. R., Some factors affecting the sulphur content of coke and gas in the
carbonization of coal. Jour. Ind. and Eng. Chem. Vol. 13, p. 33, 1921.

3l8 THE PREPARATION AND USES OF COAL

phide is formed from hydrogen sulphide where it passes over red-hot
coke. If hydrogen is passed through coke at a temperature above
600 C. a marked evolution of hydrogen sulphide occurs although the
coke had ceased to evolve hydrogen sulphide at about 600 C. The
effect of the hydrogen is to aid the decomposition of iron pyrite at a
temperature below 500 C. and the decomposition of organic sulphur
compounds at temperatures above 500 C. Hydrogen over a coke
containing 1.2 per cent sulphur was saturated, when it contained
about 0.25 pounds of sulphur per 1000 cubic feet with the coke at
900 C. Hydrogen can therefore scarcely be regarded as an agent
which could be profitably employed to remove sulphur from coke.

Apparently the gases given off in the coking process play an active
part in removing the sulphur from the coke if they can be relieved of
their load of sulphur and returned over the coke. Less sulphur was
found in the by-product coke when the gases were returned in contact
with the coking mass than in the coke where the gases were drawn
entirely away from the mass. One may predict therefore, that some
method may be devised to eliminate to quite an extent the sulphur in
the coke.

Beehive coking. The earliest forms of beehive ovens, which
get their names from their shape, were built of clay but the modern
ovens are standardized in size and form and are constructed of mas-
onry, brick and tile. Fire brick is used for lining and the space between
the lining and outside walls is filled with waste brick and other ma-
terial to prevent, as far as possible, the loss of heat to the exterior.
The ovens, which are usually 12.5 feet long by about 7 feet high
internally, are arranged in a double row and connected with a com-
mon flue, the opening to which is controlled by a damper. In some
places the hot waste gases are used for producing steam in the power
plant or for heating purposes. The cost of an individual oven in nor-
mal times runs from about $450 . oo to $500 . oo.

The oven is started at first with a wood fire and coal is added grad-
ually for from two to four days to prevent cracking the brickwork.
A small charge may then be added and the front door bricked up,
leaving holes for air. The burning of this charge, which does not
give good coke, is performed to heat the oven and the resulting ma-
terial may be rejected or used to heat other ovens. When the oven
is hot a charge is loaded in after the front door has been bricked up

BEEHIVE COKING

319

about two- thirds of the distance to the top. The charge for a stand-
ard oven is about 5 tons. The proportionate swelling of the coal on
heating varies with different coals.

In many places the coal is crushed to about \ mesh before charging,
unless it be finely divided when it comes from the mine. The charge
is carefully leveled with a leveling bar and the door bricked and

FIG. 105. Beehive ovens at the Isabella plant of the Hecla Coal and Coke Co.
courtesy of the Hillman Coal and Coke Company, Pittsburgh, Pa.)

(By

sealed up within about ij inches of the top, or far enough to admit
just about the right amount of air to burn the gas above the charge.
During the latter part of the process the oven is sealed tightly to
prevent entrance of air, which causes loss of coke by combustion.
The length of time the coke is burned depends upon the purpose to
which it is to be put. The best foundry coke is burned for about
seventy hours but about forty-five hours is the time many ovens are
run for other types of coke.

320 THE PREPARATION AND USES OF COAL

When the charge is burned the " coke-puller " places a sort of
iron sprinkler with comparatively large orifices, in the oven and
quenches the coke, applying upwards of 1000 gallons of water to each
oven. Care should be exercised so that the lower part of the oven
will not be so cooled with excess water that it will not start the fresh
charge when it is added. The coke is then drawn either by hand or
with a drawing machine and is loaded with a fork so that the fines
are separated.

The Coppee type of oven. In an effort to exclude all direct access
of air to the coking chamber Coppee introduced a retort type of oven
in 1 86 1. 1 The oven consists of narrow rectangular chambers about
30 feet long and 3^ feet high. They are built with a slight taper
towards one end to lessen the friction of discharging. The ovens
are charged at the top and the gases pass into a series of vertical flues
into which enough air is admitted to permit the combustion of the
gases. The hot gases move downwards into a sole flue and after
passing under the whole length of the oven they return to a chimney
by the sole flue of the adjoining oven. They pass over boilers to
utilize the heat and then up a chimney. The oven is discharged by
a pusher and the coke is quenched outside the oven. The advan-
tages claimed for this type over the ordinary beehive oven are: greater
yield because of exclusion of air from the coking chamber; shorter
coking period, because hot gases are utilized; saving in oven heat,
because of external quenching and use of mechanical appliances.

By-product coking. The beehive oven has long been recognized
as an extremely wasteful apparatus and the time is rapidly coming
when it will be entirely superseded by the by-product type which will
save all of the volatile constituents as well as the coke. It was thought
for a long time by metallurgists that the coke made in by-product
ovens was inferior to that made in beehive ovens, but the by-product
coke has become quite popular and it has been found that in regular
operation the consumption of by-product coke per ton of pig iron
manufactured is from 100 to 300 pounds less than of beehive coke,
in the same operation. 2 Further, the energy used in coking a ton of

1 Byrom, T. H., and Christopher, J. E., Modern coking practice. Crosby, Lockwood
and Son, 1910.

2 Sperr, F. W. Jr., and Bird, E. H Bv-product coking. Jour. Ind. and Eng. Chem.,
Vol. 13, p. 26, 1921.

BY-PRODUCT COKING

321

coal in a beehive oven is 9,388,000 B.t.u., the equivalent of 671
pounds of coal, or 33.5 per cent of the heating value of the coal, while
in the same operation in a by-product oven the energy expended is
2,408,000 B.t.u., the equivalent of 172 pounds of coal, or 8.6 per cent
of the heating value of the coal.

As pointed out above it is apparent that it is possible to produce
lower sulphur coke from a given coal in the by-product than in the
beehive oven. Coals running as high as 35 per cent volatile matter
have been used in a by-product oven although it is customary to mix
high volatile coals with lower volatile types and thus produce a suit-
able mixture. Kreisinger gives the following figures as representa-

FIG. 1 06. Semet-Solvay coke pusher and cross-section of a regenerative
oven. (By courtesy of the Semet-Solvay Co.)

tive of the composition of the coal from a number of mines used in
making by-product coke: Moisture, 2.77 per cent; Volatile matter,
34.17; Fixed carbon, 56.94; Ash, 8.99; and Sulphur, 1.37. The an-
alysis of the coke runs: Moisture, 0.79 per cent; Volatile matter,
2.80; Fixed carbon, 79.29; and Ash, 17.14. In general, coals used
run from 26 to 35 per cent volatile matter. The sulphur must not
exceed i per cent in first-grade coke, and the ash in the coal must be
less than 8 per cent if used for manufacture of first-grade coke. For
second-grade coke sulphur has been placed at 1.20 per cent as a maxi-
mum and ash in the coal at 10 per cent.

In 1893 the production of beehive coke in the United States was
9,464,730 short tons and of by-product coke 12,850 tons. In 1919
the production of beehive coke was 19,650,000 short tons and of
by-product 25,171,000 tons, 1 showing that the supremacy of the

1 Mineral Industry, p. 116, 1919.

3 22

THE PREPARATION AND USES OF COAL

beehive is rapidly waning. The by-products recovered for the year
1919 amounted to 668,200,000 pounds ammonium sulphate or its
equivalent; 251,000,000 gallons of tar; 84,800,000 gallons of crude
light oil and 367,700,000,000 cubic feet of gas.

The cost of installing a large by-product plant has been one of the
obstacles in the way of a more rapid introduction of the ovens although
they are becoming very numerous, many of them being established

FIG. 107. Semet-Solvay plant constructed for the Chattanooga Coke and
Gas Co. (By courtesy of the Semet-Solvay Co.)

in connection with the large metallurgical plants where the gas and
tar are utilized for fuel. They are also built near cities where the gas
can be utilized. The cost of some of the large plants runs from
several hundred thousand to several million dollars.

The main principle of the by-product oven is the heating of a
chamber full of coal, which is connected with a system of condensers
and stills. It is distinctly a distillation process. There are several
types of ovens, such as the Semet-Solvay, Koppers, Otto-Hoffman,
Otto-Hilgenstock, Coppee, Roberts, Willputte and Klonne. Of these
the Semet-Solvay and Koppers are the most common in America

DERIVATIVES FROM BY-PRODUCT OVENS 323

with the Otto type next. The Koppers has vertical and the Semet-
Solvay horizontal flues (Figs. 106 and 108). The modern ovens are
of the regenerative type, that is, they use the waste heat, and live
gas from the ovens to heat the regenerators which in turn heat the
air drawn through them on its way to aid combustion in the flues,
where the gas from the ovens is used to maintain heat. The direc-
tion of the current of gas or air is reversed about every half hour
and in that way the regenerators are kept hot.

The ovens are arranged in batteries and each oven is a steel cham-
ber surrounded by flues and lined with silica brick. The batteries
vary in size, but 60 ovens make a battery in the large plants and the
largest plants have 640 or more ovens. An oven of a large type is
about 30 to 36 feet long by 10 feet high while the smaller types are
only about 6 feet high. The coke is pushed out of the oven by a
pusher and taken in cars to a quenching bath. As a rule about 8
tons of crushed coal are fed into an oven with a charging machine
and it is fired for from seventeen to twenty-four hours, depending
upon requirements. A large plant will handle between 700 and 800
tons of coal per hour.

Derivatives from by-product ovens. The process of separating
the various by-products from one another is very complicated and a
vast number of derivatives are obtainable. (See chart, Fig. 5.)
The volatile constituents are drawn off the ovens and through con-
densers and scrubbers by means of powerful exhausters. The tar
is practically all eliminated from the other constituents by the re-
duction of temperature. The remaining tar is finally eliminated by
the impinging method employed in tar extractors of the impact type
in which the tar and other constituents are drawn against a combina-
tion of perforated and plain plates, the tar adhering while the more
fluid constituents pass on. The ammonia is removed by scrubbers
in which water absorbs the gas, and the oils are distilled (Fig. 108).

The common products of the ovens are coke, gas, tar and ammonia
liquor. The coke is used for metallurgical, foundry and heating pur-
poses, and the fines from the coke, known as coke breeze are burned
under boilers in power plants or other steam plants. The gas may
be scrubbed and used for illuminating purposes, or it may be used for
heating. In some cases it has been used in internal combustion en-
gines. The tar is used to a large extent as fuel, in road making,

4T^

M *
8 T

(324)

MANUFACTURE OF COKE FOR DOMESTIC FUEL

325

in waterproofing, in paints and for other purposes. By heating it
between 170 C. and 360 C. a number of derivatives may be ob-
tained which include heavy and light oils, creosote, pitch and other
constituents. The most important of the oils are benzol and toluol,
the former of which on distillation gives a number of light oils such as
gasoline and naphtha. The coal-tar dyes and numerous other val-
uable constituents are derived by further distillation. The ammonia
liquor is used chiefly for the extraction of sulphate of ammonia by
treatment with sulphuric acid. The sulphate has extensive appli-
cation in the chemical industries and in the manufacture of fertilizers.

The total value of the by-products from coke produced in the
United States in 1916 was placed at $61,931,595 of which nearly 25
million dollars were obtained from the benzol and toluol. The value
of the coke for the same year was $75,373,070.

The following figures show the amount of coal used for coking in
the United States, the average yield of coke per cent from the coal,
and the value of the coke, for the years 1915, 1916 and 1917:

Coal for ovens

Average percentage yield

Value at ovens

Beehive ovens

1915

42,278,516

65-1

$ 56,945,543

1916

55.084,958

64.4

95,468,127

1917

52,246,612
By-product ovens

63.5

159,599,864

1915

19,554,382

72.0

48,558,325

1916

26,524,502

71-9

75,373,070

1917

31,505,759

71.2

83,752,371

Of the states of the Union, Pennsylvania far surpasses all others in
production, her output being about 60 per cent of that for the country.

Manufacture of coke for domestic fuel. Some coke is now used
for domestic and steaming purposes, but 80 to 90 per cent of all coke
produced is used in the metallurgical industry. There has been a
strong desire in recent years among men interested in fuels to find a
fuel for domestic purposes with properties somewhere between those
of coal and coke.

A process has recently been tried out at Syracuse, New York, by
Donald Markle, for one of the Pennsylvania anthracite companies,
with the object of briquet ting and coking anthracite fines. Culm is

326 THE PREPARATION AND USES OF COAL

washed, the coal crushed, cemented with 14 to 25 per cent of pitch
to form briquets and then burned in an oven. The product is known
as anthrocoal and it is claimed that the experiments tried have pro-
duced a very satisfactory domestic fuel which on test was 20 per
cent more efficient in a kitchen range than chestnut coal.

The development of the process for carbonization of coal at low
temperatures has led to the production of carbocoal, a fuel contain-
ing a little more of the volatile combustible constituents of the coal,
than that contained in ordinary coke, the ratio being about 3 to i.
It, therefore, approaches anthracite as a fuel in burning longer, in
being cleaner, in producing less smoke and in standing storage better
than bituminous or other coals which lie below anthracite in fixed
carbon. It has been shown by experiment in Canada 1 that lignite
may be satisfactorily carbonized and the coked material, which is too
powdery to be used in that condition, briquetted. From a ton of
2000 pounds of this lignite 3150 cubic feet of gas, 10.2 pounds of am-
monium sulphate, 5.3 imperial gallons of tar, and 910 pounds of car-
bonized residue were obtained. The coal used contains 31.8 per
cent moisture. The carbonized products had an available heating
value 75 per cent above that of the original coal.

Bituminous coal has been treated very satisfactorily by carbon-
izing it at low temperature and briquetting the coke formed. From
coals running over 32 per cent volatile matter where carbonized at
850 to 950 P'. the following constituents have been obtained: 2

By-products per ton of coal

Dry tar 34 gallons

Gas 8457 cubic feet

Ammonium sulphate 21 pounds

Light oil from gas 1.87 gallons

Other tar oils . . 19.3 gallons

Pitch, per cent of tar 43

The average analysis of the briquets made from the residue is as

follows:

Volatile matter 3.8 per cent

Fixed carbon 85 . i "

Ash n. i "

1 Stansfield, Edgar, Carbonization of Canadian lignite. Jour. Ind. and Eng. Chem.,
Vol. 13, p. 17, 1921.

2 Curtis, H. A., The commercial realization of the low-temperature carbonization of
coal. Jour. Ind. and Eng. Chem., Vol. 13, p. 23, 1921.

MANUFACTURE OF COKE FOR DOMESTIC FUEL 327

The production of such fuels has been put on a commercial basis
within the last couple of years. A description of a plant at Clinch-
field, Virginia, capable of treating 500 tons a day has been published
by Eshereck. 1 In this plant there are 24 primary, low-temperature,
and 10 high- temperature retorts. The primary retorts are arranged
in four batteries and the crushed coal is fed into them from overhead
bins. The semi-carbocoal is taken from these retorts, which are con-
tinually in operation and carried to storage bins in the briquetting
plant. It is then ground, mixed with pitch, fluxed and briquetted
on heavy roll presses. The briquets are carried on a long conveyor
and then by a steel charging car to the secondary retorts. The
finished briquets are dumped from the secondary retorts, which are
inclined, and later quenched.

The by-products are carried through the same general process of
condensing, scrubbing and distilling as in the other by-product
processes described above. The process outlined is known as the
Smith Process. It is found that the yield of carbocoal runs from 65 to
72 per cent of the coal used, depending upon the character of the coal,
and on account of the low temperatures at which the primary retorts
are heated there is a much greater yield of tar oils than in ordinary
by-product operations. In some cases it is over seven times as great.
There is practically no production of pitch, but the other constituents
are similar in quantity to those derived from a by-product coke oven.

It seems very probable that this method of producing fuel will
have a rapid development and that in the future practically all of
our fuels will be treated in some such manner. It is also probable
that some of the liquid by-products obtained from this process will
be used in our homes as domestic fuel.

1 Eshereck, George, Jr., Prospect that soon no coal will be used without preliminary
devolatilization. Coal Age, Vol. 18, p. 327, 1920.

CHAPTER XII

THE GEOLOGIC AND GEOGRAPHIC DISTRIBUTION

OF COAL

From a geological standpoint coal is distributed through the vari-
ous formations from the Upper Devonian to the Pleistocene although
the latter contains only low-grade coal and the former a very limited
quantity. In the later Pleistocene and the Recent rocks large beds
of peat not yet changed to coal are found in many countries.

The earliest coal deposits known are in the Upper Devonian in
northern Russia and on Buren Island, Norway, and they are coincid-
ent with the first great development of land plants on the earth.
Between the Devonian and Pleistocene there is not a geological system
without at least some coal somewhere on the globe. Certain systems,
however, carry the bulk of the valuable coal. Taking the earth as
a whole the Carboniferous is the most important for high-grade coal
while the Tertiary contains most of the lignite. The Mississippian,
or Lower Carboniferous, as it is known outside of the United States,
carries valuable coal in Virginia, Scotland, Spitzbergen, Russia,
Corea and Manchuria. The Permian is very important in the South-
ern Hemisphere, particularly in Australia, India and Africa, and this
system also carries some coal in Europe, the United States and eastern
Asia. The Triassic is a prominent coal-bearing system outside of
America as it contains the coal of Tasmania, some in Queensland and
New South Wales, Australia, considerable in Hungary, Austria,
Japan, China and South Africa and a small field in North Carolina and
Virginia, in the eastern United States. The Jurassic is not important
in America outside of Alaska and small areas in the Yukon but it
is of great importance in China and Corea, and it is also coal-bearing
in New Zealand and Austria. The Upper Cretaceous is one of the
great coal-bearing periods in the earth's history especially in western
North America and Central Europe, while the Lower Cretaceous, or
Comanchean of some of the United States geologists, except in its

328

GEOLOGIC AND GEOGRAPHIC DISTRIBUTION 329

earlier formations, is probably the most barren of coal of all the
systems from the Lower Carboniferous onward. It carries good
coal in western Canada and in limited areas in the western states, a
little in South Australia, and low grade bituminous coal in Spain.
The abundance of coal in the Upper Cretaceous and Tertiary, follow-
ing its scarcity in the Lower Cretaceous repeats the conditions exist-
ing in the Lower and Upper Carboniferous. The Lower Carbon-
iferous and the Lower Cretaceous were periods of extension of the sea
over the continents, except in the earlier stages of the Lower Creta-
ceous when many lakes and swamps existed, while it gradually with-
drew during the following periods leaving great flat areas covered
with swamps, as in the case of our coastal plains of the present day.
Extension of the sea and marine deposition or, on the other hand, very
high lands with rapid erosion do not go together with coal formation,
but the gradual restriction of the sea and the formation of coal work
together harmoniously.

The period of coal formation begun in the Upper Cretaceous con-
tinued into the Tertiary and most of the lignite of the world was
formed in that period. Every continent contains some coal of this
age and America and Europe have very large supplies. There is
some good anthracite and bituminous coal of Tertiary age but most
of the coal outside of the mountain regions is of the lignite type be-
cause it has not been changed to a higher form by heat or pressure
or by these two agencies combined.

As to the occurrence of coal in rocks older than the Upper Devon-
ian, the question is often asked why coal should not exist in these
older formations. The only explanation is that the land plants had
not reached a stage in their evolution which made them sufficiently
abundant and widely distributed to form extensive deposits of coal.
Deposits of vegetal matter were made in earlier formations, even
back in the pre-Cambrian, as shown by beds of black shales and
deposits of graphite, but these were of quite limited extent and ap-
parently made from aquatic plants. It is also true that from the close
of the pre-Cambrian until the Carboniferous not only the American
continent but some of the others as well were largely covered with the
sea and marine deposits were the main types being formed. It re-
quires proper topographic conditions as well as an abundance of land
plants to produce coal.

330

GEOLOGIC AND GEOGRAPHIC DISTRIBUTION

TABLE OF GEOLOGICAL FORMATIONS USED IN AMERICA,

EUROPE AND AUSTRALIA WITH SPECIAL REFERENCE

TO COAL-BEARING SERIES

America

Great Britain

France

Germany

Australia

R.ecent

Recent

Alluvium

decent

Pleistocene

Pleistocene or

3 leistocene

Diluvium

Pliocene

Pliocan

3 liocene

Miocene

Miocan

Miocene

Oligocene

Oligocan

Oligocene

Eocene

Paleocan

Socene

Cretaceous (Upper)

Cretacique

Kreide

Cretaceous

(Upper)

(i) Laramie

(i) Upper Chalk

Neocretacique

Ober Kreide

(2) Montana

(2) Lower Chalk

(3) Colorado

(3) Marls

(4) Dakota

(4) Upper Green-

sand

(5) Gault

Comanchean or

Cretaceous ( Lower } f Eocretacique

Unter-Kreide

Cretaceous

Lower Cretaceous

(i) Lower Green-

(i) Gault

(Lower)

sand

(2) Wealden

(2) Weald

Jurassic

Jurassique

Jura

furassic

(i) Upper

(i) Oolite

(i) Neojurassique

(i) Malm

(2) Middle

(2) Lias

(2) Mesojurassique

(2) Dogger

(3) Lower

(3) Eojurassique

(2) Lias

Triassic

(Newark series)

Triassic

Friassique

Trias

Triassic

(i) Rhaetic

(2) Keuper

(3) Bunter

(3) Muschel-

kalk

(4) Bunter

GEOLOGIC AND GEOGRAPHIC DISTRIBUTION

TABLE OF GEOLOGICAL FORMATIONS (Continued)

331

America

Great Britain

France

Germany

Australia

Permian (Dunkard)

Permian or Dyas

Permien

Perm

Permo-Carbon-

iferous

(a) Thuringien

(a) Zechstein

(a) Igneous series

Upper Barren

(b) Saxonien

(b) Rothlie-

(b) Upper or

Measures

gende

Newcastle

Coal Measures

/ \ y%

Carboniferous

Carboniferien

Karbon

^6^ .L/empsey
series

(d) Middle Coal

(l) Pennsylvanian

(i) Upper Carbon-

Oberkarbon

Measures

or Upper Car-

iferous

() Upper Ma-

boniferous

rine Series

(a) Monongahela

(/) Lower or

or Upper Pro-

(a) Stephanien or

(a) Ottweiler

Greta Coal

ductive

Ouralien

Measures

(b) Westphalien or

(b) Saarbrucken

(g) Lower Ma-

(b) Conemaugh

Muscovien

rine Series

or Lower Bar-

(a) Coal Measures

ren Measures

- Lower Produc-

tive Measures

(d) Pottsville or

(b) Millstone Grit

Millstone Grit

(2) Mississippian

(2) Lower Carbon-

Dinantien

Unterkarbon

Carboniferous

or Sub-Car-

iferous; Culm,

Kulm or Koh-

boniferous

or Limestone

lenkalk

(a) Mauch Chunk

series

(b) Pocono

Devonian

Devonienne

Devon

Devonian

Silurian

Silurien

Ober-Silur

Silurian

Ordovician

Lower Silurian

(i) Goth-Landien

Unter-Silur

Ordovician

(2) Ordovicien

Cambrian

Cambrien

Kambrium

Cambrian

Proterozoic or

Pre-Cambrien or

Eozoisch or

Algonkian

Archeen

Archaozoisch

Archaeozoic or

Archean

332

GEOLOGIC AND GEOGRAPHIC DISTRIBUTION

The following table shows the geological distribution of the different
types of coal on the various continents and their relative abundance.
More detailed tables are given for the individual continents where the
coal resources of those continents are described.

TABLE SHOWING THE GEOLOGICAL DISTRIBUTION OF
COAL BY VARIETIES

Period

North
America

South
America

Europe

Asia

Africa

Oceania

Quaternary

Tertiary

SBLAB

BLB

BBL

Cretaceous

ABLBS

Jurassic and Triassic

ablb

B 1

ASBL

Permian

A B

B c

Permo-Carboniferous

ABB

AB1

Carboniferous

ABSB

ABcl

Lower Carboniferous .

aBs

ABS

Devonian

A, Anthracite; S, Semibituminous; B, Bituminous; B, Subbituminous; L,
Lignite, including brown coal; C, Cannel. Capital letters are used to indicate
large and important deposits and lower case for small or unimportant deposits
of the same variety

Geographically, coal is almost universally distributed as there are
very few countries which do not have some coal. Even Antarctica
has a considerable supply. There are a few countries, including
Egypt, Thibet and Bolivia, which do not report any workable de-
posits. Norway has little or none outside of Spitzbergen and her
other northern islands. Switzerland has had very small supplies
and they are said to be nearly exhausted. Many other countries
have very little coal in proportion to their political importance.
Such are, for example, Italy, Roumania, Sweden, Brazil and the Argen-
tine Republic. Japan is poorly supplied in proportion to her popula-
tion and she will no doubt expect to control large areas on the main-
land of Asia to take care of her industrial development, because history

GEOLOGIC AND GEOGRAPHIC DISTRIBUTION

333

has shown that the accessibility of large coal supplies is an essential
factor in the great industrial development of any country. A glance
at the table showing the coal resources of the various continents will
show that Africa and South America are not well supplied with coal,
although no doubt further geological work on these continents will
reveal much larger resources than are here indicated. North Amer-
ica is lavishly supplied, and Europe, Australia and eastern Asia have
plenty. The distribution of the coal deposits will have a very im-
portant bearing on the future economic history and commercial
relations of these continents and especially on those of certain
countries. This is well illustrated by the international problems
arising from the distribution of coal during the war and immediately
following it.

The following table will show the coal resources of the world by
continents, in so far as geological data exist regarding them. This
is the best and most complete estimate which has so far been com-
piled.

0) COAL RESOURCES OF THE WORLD BY CONTINENTS
(In million metric tons; i metric ton = i .1023 short tons)

Class A

Classes B and C

Class D

Anthracite and
some dry coals

Bituminous coals

Subbituminous,
brown coals and
lignites

Totals

Oceania . .

6cq

1 33 4.8l

36 27O

I7O 4.IO

Asia
Africa

407,637

11,662

760,098
4.c>.123

111,851
I O<4.

1,279,586
e>7 83Q

America

22,542

2,271,080

2 811 906

5TQC C28

Europe

<?4,346

603,162

36 682

784. IQO

Totals

4.Q6 84.6

3QO2 Q4.4.

^yy/>/ u o

toy/too^

( l ) From the Coal Resources of the World. Twelfth International Geologi-
cal Congress, Morang & Company. For detailed discussion of classes of coal
see Classification of Coals, Chapter V.. The above estimates include all seams i
foot and over in thickness and less than 4000 feet deep; and 2 feet and over in
thickness and between 4000 and 6000 feet below the surface.

The outstanding features indicated in this table are the tremendous
amount of coal in America and anthracite in Asia. The latter is
mostly in China. It seems probable, however, that much coal has

334 GEOLOGIC AND GEOGRAPHIC DISTRIBUTION

been classed as anthracite in China which will turn out to be semi-
bituminous or high-grade bituminous coal. Nevertheless, China far
surpasses all other countries combined in her resources in this variety
of coal. America has little anthracite in comparison with her re-
sources in bituminous and brown coals.

The following table from Mineral Industry shows the coal produc-
tion of the various countries of the world from the year 1911 to 1916.
During the war the production of some countries almost ceased and
since the beginning of the war it has been impossible to secure accurate
data concerning the production of many countries. As indicated by
the table, the output of the United States has increased rapidly and
her production has almost passed the 6oo,ooo,ooo-ton mark. She
has also become the leading exporter of coal since the exports of
Great Britain have decreased from over 75,000,000 tons before the
war to less than 20,000,000 in 1919, while those of the United States
have more than doubled and are now said to be over 30,000,000 tons
per annum. Few of the great industrial countries can look forward
to exporting high-grade coal in very large quantities for an indefinite
period because of the rate of increase in domestic requirements and
the exhaustion of the more accessible seams.

GEOLOGIC AND GEOGRAPHIC DISTRIBUTION

335

0) COAL PRODUCTION OF THE WORLD IN SHORT TONS
FOR YEARS 1911-1916

Country or State 1911

1912

1913

1914

1915

1916

United States 496,371,126
Great Britain 304,518,927
Germany 258,223,763
Austria-Hungary . . 54,960,298
France 43,242,778

534.466,580
291,666,299
281,979,467
56.954,279
45,534.448
33.775.754
25.322,851
21,648,902
16,471,000
16,534,500
14,512.829
10,897,134
7,591,619
4,559,453
2.438,929
1,901,902
1,470,917
1,010,426
982,396

940,174
909.293
73L720
664,334
525,459

622,669
471,259
397,149
335.OOO
330,488
307,461
306,941
324,511
216,140

59, 987

16,938
(a) .12,000

2,998

569,960,219
321,922,130
305,714,664
59,647,957
45,108,544
37.188,480
25,600,960
23,988,292
18,163,856
15,432,200
15,012,178
11,113,865
8,191,243
4,731,647
2,115,834
2,064,608
1,362,334
1,162,497

927,244

772,802
668,524
609,973

453,136
401,199

351,687
301,970

237,728

61,648
49,762

27,653
13,355

513,525,477
297,698,617
270,594,152
(d) 53,396,400
33.360,885
36,414,560
(a) 19,000,000
21,700,572
18,430,974

13,594,984
11,663,865
7,778,706
4,897,360
2,548,664
1,928,540

1,180,825

861,265
691,640
699,217

440,905
404,143

357,515
312,897

391,394

68,130
128,505

32,743

531.619.487
283.570,560
259,139.786
(d) 52,679,712
19,908,892
31,158,400
15,691,465
22,596,750
19,156,404

13,269,023
10,582,889
9,275,083
5,414,475
2,208,624
2,262,148

1,147,186

1,042,748
588,104
727,531

454,432

321,066
318,563

458,934
66,000

597,474,000
287,110,153

50,801,602

(a) 19,900,000
22,189,969
19.325,637
(o) 24,000,000
14,461,678
11,262,420
11,200:370

6.05/.727
2,527,991

I 016,654

1,439,538
463,074

457,262

337,709
35L703

491,532
62,244

Russia 29,361,764
Belgium 25 411,917

Japan 19.436,536

India 13.494. 573

China 16,534,500

Canada . . .11,323,388

New South Wales . .9,374,596
Transvaal (&) 7,112,254

Spain 4,316,245

New Zealand 2,315,390
Holland 1,628,097

Chile i 277 191

Queensland 998,556
Mexico (a) 1,400,000

Bosnia and Herze-
govina 848,510

Turkey 799,168

Italy 614,132
Victoria 732,328
Orange Free State (e) 482,690
Dutch East
Indies (a) 600,000
Indo-China (a) 460 ooo

Sweden 343 707

Servia . 335 495

Western Australia (a) 300,000
Peru (o) 300 ooo

Formosa 280,999
Bulgaria 270,410

Rhodesia 212,529

Korea 138,508

Tasmania (a) 70 ooo

British Borneo (a) 100,000
Spitzbergen . . 44 092

Brazil 16 535

Portugal (a) 10,000

Venezuela (a) 10,000
Switzerland 8,267
Philippine Islands. . (a) 2,000
Unspecified (0)1,016,947

Totals. . 1,309,574,000

( J ) From Mineral Industry, 1917.

(o) Estimated, (b) Transvaal, includes Natal and Cape of Good Hope and figures are only for
coal sold, (c) Approximate. (d) Hungarian production estimated at 10,000,000 short tons, (e)
Represents only coal sold, probably 10 to 12 per cent less than production.

CHAPTER XIII
THE COAL FIELDS OF THE WORLD AMERICA

Introduction

America is here considered as two units North and South.
America undoubtedly has the greatest coal deposits of the world,
but it is a striking fact that so far as our knowledge of the resources
of the two continents extends the southern contains only about
six-tenths of one per cent as much coal as the northern continent.
A better knowledge of the geology of South America will no doubt
extend her known resources but the disparity between the future
supplies of the two continents will profoundly affect their trade
relations.

North America

In a discussion of North America's coal deposits there are included
those of Canada, Newfoundland, the West Indies, the United States,
including Alaska, Cuba, Mexico and Central America. The following
table shows the relative resources of these countries in so far as we
have reasonably definite knowledge regarding them. Mexico has
considerable good coal but her resources are not well known outside
of a few areas explored by American or European companies.

This table shows the great extent of the coal supplies of the United
States in those types of coal which are used so much in the industries.
Canada is also unusually well supplied with bituminous coal and with
lower grades but she is deficient in anthracite and in related high-
carbon coals. This deficiency will probably not be so keenly felt in the
future, however, as it has been in the past, because with the develop-
ment of the use of partially devolatilized fuels such as carbocoal a
substitute for anthracite will be provided in many parts of the country.
The coal deposits of Canada and the United States, especially of the
latter, have been gone over fairly well, and the above estimate of the
resources may be regarded as comparatively accurate. Considerable

336

NORTH AMERICA

337

changes will be made, however, in these figures as more geological
work is done, particularly in those for Canada since there are very
large areas in Canada on which little field work has been completed.

ESTIMATE OF THE COAL RESOURCES OF NORTH AMERICA
(In million metric tons; i metric ton = i .1023 short tons)

Class A

Classes B and C

Class D

Anthracite and
some dry coals

Bituminous
coals

Subbituminous
coals, brown coals
and lignites

Totals

Ne wf oundland .

500

Canada
United States . . .
Central America

2,158
19.684

283,661

i,955,52i

948,450
1,863,452
4

1,234,269
3,838,657
5

Total

21,842

2,239,683

2,811,906

Z, O73, 4^1

Table from The Coal Resources of The World, Morang & Co., 1913. A detailed
statement regarding the different classes of coal may be found in Chapter V
on Classification of Coals. The estimates include all seams i foot and over
in thickness and 4000 feet or less in depth; and all seams 2 feet and over in thick-
ness and between 4000 and 6000 feet in depth.

The geological age of the coals in North America ranges from
Mississippian, or Sub-Carboniferous, to Pleistocene, the main periods
for their formation being the Upper Carboniferous, or Pennsylvanian,
the Cretaceous, and the Tertiary. The table given below shows their
geological distribution.

338 THE COAL FIELDS OF THE WORLD AMERICA

GEOLOGICAL AGE OF COALS OF NORTH AMERICA

Canada

United States

Newfoundland

Mexico

Central America

Trinidad

o3
>
O

New Brunswick

Ontario

Manitoba

Saskatchewan

1
1

Yukon Territory

N. W. Territory

J-

Atlantic Coast
Region

Interior Province

Great Plains
Province

Rocky Mountain
Province

Pacific Coast
Province

Pleistocene

1
1

Pliocene

Miocene

aAB

Eocene

B
L

aa
BB
L

bBL

Tertiary undifferen-
tiated

b
1

AA
BB

Upper Cretaceous

Lower Cretaceous

a
A
B

Jurassic

bBl

Triassic

a
a

Permian

Pennsyl vanian

Mississippian

A. Anthracite; A. Semianthracite; S. Semibituminous; B. Bituminous; B. Subbituminous; L.
Lignite and brown coal. Capital letters indicate important deposits and lower case relatively unim-
portant to unworkable deposits of the same type.

COAL AREAS OF CANADA

PLATE XI. The Coal-fields of Canada. (i

D. B. Bowling Canadian Geological Survey.)

THE COAL DEPOSITS OF CANADA

339

THE COAL DEPOSITS or CAN AD A 1

The production, and the geological age, of the coals of Canada
have been given in the preceding tables and the following table sums
up the distribution and the characters of the coals in the various
provinces as worked out by D. B. Dowling.

COAL RESOURCES OF CANADA

District

Actual Reserve
Calculation based on actual thick-
ness and extent

Probable Reserve
(Approximate estimate)

Area Sq.
Miles

Class of
coal

Metric tons
(i metric ton =
1.1023 short tons)

Area Sq.
Miles

Class of
coal

Metric tons

B 2

2,137,736,000

B 2

4,891,817,000

Nova Scotia . . .

174.31

273 . 5

50,415,000

20,000,000

New Brunswick. .

121

B 2

151,000,000

Ontario

D 2

25,000,000

Manitoba

160,000,000

Saskatchewan

306

D 2

2,412,000,000

13,100

D 2

57,400,000,000

D 2

^26,450,000,000

382,500,000,000

464,821,000,000

Alberta.

25,300

1,197,000,000

56,375

139,161,000,000

B 2 B!

2,026,800,000

B 2 Bi

43,022,600,000

A 2

669,000,000

A 2

100,000,000

A 2 B 2

23,653,242,000

A 2 B 2

40,807,700,000

British Columbia

439 j

118,000,000

5,595

2,300,000,000

D 2

60,000,000

DiD 2

5,136,000,000

1,800,000,000

Yukon

2,840

A 2 Bs

250,000,000

North-West

Territories

300

DiDz

4,690,000,000

D 2

4,800,000,000

Arctic Islands

6,000

B 2 Bs

6,000,000,000

Totals

26,219.31

*4l4,8o4,l93,ooo

82,662.5

801,966,117,000

* 20,000,000 tons deducted for the amount of coal already exhausted in Alberta. Table from Coal
Resources of the World. For details of classes of coal see Classification of Coals, Chapter V. This table
contains all seams of I foot or over to a depth of 4000 feet.

1 For detailed accounts of the coal deposits of Canada see The Coal Resources of the
World, Twelfth International Geological Congress, (Morang & Co.), An Economic In-
vestigation of the Coals of Canada, by J. B. Porter and R. J. Durley, Department of
Mines, Canada; The Coals of Canada, by D. B. Dowling, Memoir 59, Canadian Geol.
Survey, 1915; and The Coal Fields of British Columbia, by D. B. Dowling, Memoir 69,
Canadian Geol. Survey, 1915.

340 THE COAL FIELDS OF THE WORLD AMERICA

In addition to the figures mentioned here there might be added
17,499,000,000 metric tons of coal of Class B 2 which occurs in seams
over 2 feet thick lying at a depth between 4000 and 6000 feet, in the
provinces of Nova Scotia, Alberta and British Columbia.

From the accompanying map (Plate XI) it will be observed that
the coal deposits of the Dominion are almost all located in the ex-
treme eastern and in the western parts of the country. Quebec and
Ontario, the most populous and the most important of the prov-
inces commercially have no good coal and they receive most of their
supply from the United States. Quebec is without coal of any kind
and Ontario has a few million tons of low-grade lignite in the inter-
glacial deposits south of James Bay. Nova Scotia on the east and
Alberta and British Columbia on the west have high-grade coal in
large quantities while Saskatchewan and Alberta have very large
resources in lignite and subbituminous coal.

Nova Scotia. The coal of Nova Scotia is all of Pennsylvanian,
or Upper Carboniferous, age except for thin and unmined seams in
the Mississippian, or Lower Carboniferous. Thin seams occur in
the Millstone grit but most of the coal lies above this formation.
There are five important areas producing coal the Joggins and
Springhill areas in the Cumberland field; the Pictou, Inverness
and Cape Breton, or Sydney, fields. In the Joggins area there are
two seams 3 to 5 feet in thickness, and the beds are inclined at angles
of as much as 50. The coal is of fairly good quality but is high in
ash. This area has been famous for its buried Carboniferous trees
which are abundant in the sandstones of the Coal Measures. The
Springhill area is considerably faulted and it seems to represent the
central part of the basin in which the Joggins seams were laid down.
There are a number of seams of which five can be mined and they
make up a total of about 50 feet of coal, the thickest seam reaching
13 feet. In the Pictou field there is a little coal in the Millstone grit
and in the Permian, but all the workable coal occurs in the Coal
Measures proper, in two large fault blocks. One fault has a down-
throw of about 2600 feet. There are four seams in the Westville
area of this field varying from 6 to 18 feet in thickness and separated
from one another by from 90 to 260 feet of strata including some
beds of oil shales. As a rule the beds dip gently. In the Stellar ton
area of the Pictou field there are 9 seams, some of which are very

NOVA SCOTIA 341

thick. The Main seam varies from about 6 feet to 45 feet in thick-
ness and the Deep seam from 20 to 33 feet. The other seams are
rather thin. There is one bed of oil shale with a coal seam, in this area.
It is 5 feet in thickness and it was formerly mined for the extraction
of oil.

FIG. 109. Allen Shaft, near Stellarton,Pictou coal field, Nova Scotia.
(Photo by H. Ries.)

The Inverness field is largely under the sea. The measures dip
seaward at from 12 to over 75-and the seams mined run about 6 to
7 feet in thickness.

In the Sydney field, which occupies the northern part of Cape
Breton County the Coal Measures dip gently seaward, being disturbed
by only small folds. They have been mined on the slope under the
sea for more than a mile from the shore. The number of seams in
this field varies from i to 12 with an aggregate thickness of coal

342

THE COAL FIELDS OF THE WORLD AMERICA

from i foot to 46 feet. It is expected that the workings will in time
extend nearly 3 miles from the shore.

New Brunswick. In New Brunswick the upper members of the
Pennsylvanian are lacking. The Millstone grit is widely distributed
over the province and it contains a few thin seams of which one is
worked where it runs around 18 inches and over in thickness. The
seams are shallow, the coal is high in ash and sulphur but lends it-
self readily to hand picking. A little anthracite is reported from Le-
preau in St. Johns County.

FIG. no. Coal seam (retouched) in sea cliff on coast of Nova
Scotia. (Photo by H. Ries.)

Ontario. There is a small area of about 10 square miles along
the lower part of the Moose River/ south of James Bay, which is
underlain by lignite. This coal was formed in an interglacial period
and it lies between two beds of boulder clay. It is suitable for future
briquetting operations. There are no Carboniferous rocks in Ontario
and Quebec. The formations are largely pre-Cambrian, except for
some older Palaeozoics in the southern part of Ontario and around
James Bay.

ALBERTA 343

Manitoba. In the Tertiary rocks capping a hill called Turtle
Mountain and in adjacent hills along the International Boundary
there are some seams- of lignite. The eastern part of Manitoba is
covered with pre-Cambrian rocks and the western portion chiefly by
marine Cretaceous.

Saskatchewan. The coal of Saskatchewan occurs in the Ter-
tiary and Upper Cretaceous formations. The Tertiary formations
seem to correspond to the Fort Union lacustrine and land-formation
stage of the Eocene in North Dakota, and they are found in the hilly
country in the southern part of the province. The strata lie prac-
tically flat except for a syncline under the Souris River Valley and the
seams outcrop along ravines and on hillsides. A good deal of coal is
mined in the Souris Valley region and in a number of other places,
and wagon mines are common as many of the western farmers dig
their own coal. The Tertiary coal is practically all lignite and the
maximum thickness of the seams is about 20 feet. The Cretaceous
coals occur in the Belly River formation of the Upper Cretaceous
along the Saskatchewan River, in the western part of the province.
The coal lies from 200 to 300 feet below the surface and there are at
least two seams about 4 feet and 8 feet thick respectively. They
are not uniform in thickness or regular in distribution. This coal
also is lignite. A little lignite occurs in the Middle Cretaceous south
of Lac la Rouge.

Alberta. In the province of Alberta coal occurs in the Kootenay
series of the Lower Cretaceous; in the Belly River series, correspond-
ing to the St. Pierre of the Montana series of the Upper Cretaceous;
and in the fresh-water deposits of the Edmonton formation, corre-
sponding to the Fort Union beds of the Eocene.

The Kootenay series, regarded as lacustrine and terrestial in origin,
contains the best coals of Canada, they being bituminous to an-
thracite. It lies deeply buried beneath the younger sediments ex-
cept where it is brought to light in the folds along the foothills or in
the great fault blocks of the Rocky Mountains. Its thickness varies
from 200 to about 3000 feet. The coal-bearing area in Alberta ex-
tends from tlre International Boundary northward beyond the Atha-
basca River and while little development work or even prospecting
has been done in much of this great area, several very important
mining districts have developed. The most important of these is in

344

THE COAL FIELDS OF THE WORLD AMERICA

the region of Crowsnest Pass on the Crowsnest branch of the Can-
adian Pacific Railway. Mines occur at several places in the Blairmore-
Frank region. A half dozen seams occur, ranging from 3 to 17 feet in
thickness. It was at Frank that the famous landslide occurred which
carried away a section of Turtle Mountain. It destroyed a number
of houses in the town, killing ninety-three people, and it buried
the railroad through the valley, (Fig. in). The track was so deeply

M* . * .

FIG. in. D6bris from the landslide at Frank, Alberta, partly covering
the town. (Photo by E. S. Moore.)

buried that a new line was constructed over the debris which con-
sisted chiefly of great blocks of limestone. The lower portions of
the mountain are composed largely of shales and coal seams, while
the upper portion contains heavy beds of limestone. The mining
operations, which had been carried well through the mountain,
apparently disturbed the overlying strata and a large crack devel-
oped which caused a tremendous mass of rock to break away, slide
down the mountain and across the valley.

In the Coleman area there are three seams as much as 8, 10 and 16

ALBERTA

345

feet in thickness, respectively, within a thickness of 300 feet of strata.
In the Livingstone basin lying a short distance northward from the
Blairmore-Frank region, there are in Cat Mountain as many as twenty-
one seams with a total of about 125 feet of coal. On the west fork of
the McLeod River southeast of Folding Mountains there are four seams

CROWSNEST COAL AREA

SCALE OF MILES

FIG. 112. Map of the Crowsnest coal area. (After D. B. Bowling.)

in the Folding Mountain anticline on the eastern limb and they vary
from 2 feet to 28 feet in thickness. On the western limb a combina-
tion of seams forms one mass as much as 50 feet thick.

In the Cascade area there is a continuous coal field extending for
about 90 miles from south of the Kananaskis River northward to near

346 THE COAL FIELDS OF THE WORLD AMERICA

the Saskatchewan River. This is a great fault block with a fault
running along the western edge of the coal field. In some portions
there are between 15 and 20 seams of coal with a maximum aggregate
thickness of nearly 100 feet. Remnants of a very extensive coal-
bearing area are found along the Bow River and there are mines at
Canmore. At Bankhead, not far from Banff, semi-anthracite and
anthracite are mined, and mines were formerly worked at Anthracite.
These beds have been highly squeezed. Other important areas in
Alberta are the Bighorn, Brule Lake, Nikanassin, Muskeg River,
Shunda Creek, Costigan, and Moose Mountain in the foothills near
Calgary. In Folding Mountain the beds are highly folded so that
they are practically vertical.

FIG. 113. Structure section through the Blairmore-Frank region, Alberta, i,
Devono-carboniferous; 2, Lower cretaceous or Jurassic (Fernie shales); 3, Coal
measures; 4, Equivalent of flathead beds; 5, Volcanic ash and agglomerates; 6,
Upper cretaceous and laramie; 3-6, Cretaceous. Scale 4 miles = i inch. (After
D. B. Dowling, Canadian Geol. Survey.)

The abundance and high quality of the coal in western Alberta and
the adjoining portion of British Columbia make this region the most
promising coal-mining region of Canada. There is a great deal of
good coking coal.

The Belly River formation underlies about 16,000 square miles in
eastern Alberta. The best coal in this formation is being mined at
Lethbridge. The coal improves as the mountains are approached.
Around Medicine Hat two seams, each about 5 feet thick, are exposed
along the Bow River. In the vicinity of Calgary the Belly River
formation is 'struck at depths of from 2560 to 2875 feet and the coal
varies from 4 to 7 feet in thickness. At Edmonton the depth is about
1400 feet and the coal about 6 feet thick. In the Peace River Valley
there is some coal in the Dunvegan series supposed to be equivalent
to this formation. There is much coking coal in the Belly River for-
mation.

ALBERTA

347

The Edmonton (Eocene) series occurs in a large synclinal basin
which runs nearly parallel to the Rocky Mountains and extends over
about 4 degrees of latitude. The dips are steep on the western and low
on the eastern limb of the basin and the basin flattens out to the north-
westward. At Calgary there is a seam of lignite about 13 feet thick

FIG. 114. Peaks behind Canmore, Alberta. About two-thirds of mountain face is
Palaeozoic strata thrust over folded Mesozoic coal measures. (Photo by H. Ries.)

under cover of 1800 feet of poorly consolidated sandstone and clay.
On the North Saskatchewan, west of Edmonton, a 25-foo.t seam out-
crops and on the Grand Trunk Pacific Railway line at the Pembina
River crossing it splits into two seams each 10 feet thick. About
500 feet below this seam several smaller seams occur over several

348 THE COAL FIELDS OF THE WORLD AMERICA

thousand square miles and they are mined at Edmonton, Tofield
and at other places between Edmonton and Calgary. The coal varies
from lignite in the northwestern part of the basin to a subbituminous
and coking coal in the foothills of the Rockies.

British Columbia. 1 The coal deposits of this province are grouped
by Dowling under the five following heads: Southern, Central and
Northern British Columbia, Vancouver Island and Queen Charlotte
Islands. In the Southern district is located the Crowsnest area which
is a basin of about 230 square miles around which lower beds have been
uplifted and then eroded on a large scale leaving the coal field as an
elevated plateau. The coal occurs here, as elsewhere in the Rocky
Mountains, in the Kootenay series of the Lower Cretaceous and
most of the better seams occur in the lower 2000 feet. It is said,
however, that these upper seams are very largely cannel or other high
volatile coals.

The following is a tabulation of the seams in this area:

At Morrissey 23 seams with 216 feet of coal in 3676 feet of measures
At Fernie 23 seams with 172 feet of coal in 2250 feet of measures
At Sparwood 23 seams with 173 feet of coal in 2050 feet of lower measures
At Sparwood 24 seams with 43 feet of coal in 2015 feet of upper measures

At Corbin a seam 80 feet thick is worked. The coal is in places
highly faulted and folded and it is worked from tunnels. The coal-
bearing strata occupy a basin which is in a hill, and on top of the hill
there is so little cover that the coal, which is here 125 feet thick, is
stripped and mined by steam shovels.

The Flathead River area lying about 12 miles north of the Inter-
national boundary gives promise of being a very important field
for its size. It is probably a faulted block with the strata dipping only
about 20 and exposing four seams which are 16, 20, 30 and 50 feet
thick, respectively. The Upper Elk River area north of the Crows-
nest area will probably be an important field as there are as many as
eighteen seams in one section and there is an aggregate of 182 feet of
coal in 1200 feet of strata. One seam reaches 31 feet in thickness.
The coal in this area as in the others mentioned above is high-grade
bituminous coal and it is used largely for coking.

At Princeton on the Similkameen River there is a small basin con-

1 Coal Fields of British Columbia, Compiled by D. B. Dowling, Memoir 69. Geol
Survey, Canadian Department of Mines, 1915.

BRITISH COLUMBIA 349

taining lignite of Oligocene age. There are as many as seventeen
seams in one section and the thickness varies from i foot to 18 feet.
South of Tulameen similar lignite of Oligocene age occurs with two
or three seams from 1 2 to 20 feel thick. In the Nicola and Quilchena
basins there are also Oligocene deposits. Several collieries have been
opened near the mouth of Coldwater Creek in the Nicola basin and in
that region four seams running from 5 to 12 feet in thickness are mined.
The coal is used for locomotives as it is of better grade than the lig-
nite in the other regions. The basin is considerably broken by
faults and it has been overlain by basalt flows.

In the Central British Columbia region a number of coal deposits
occur but many of them have not been proven to be of special im-
portance. In the valley of the Bear River bituminous coking coal
was found along the Grand Trunk Pacific Railway in three seams
running from 4 feet to 9 feet in thickness. It is of Tertiary age. On
the southern tributaries of the Skeena River the Lower Cretaceous
rocks carry a few seams of mineable bituminous coal. In the Telka
River area some thick seams of coal, 19, 24 and 13 feet in thickness
occur. The coals are reported to be of coking quality.

Several areas of coal-bearing rocks occur in the Northern British
Columbia district. In the Groundhog Mountain area on the head
waters of the Skeena, semianthracite coal occurs in Lower Cretaceous
rocks of the Skeena series, resting on Jurassic volcanics. The area
is greatly broken by faults. In the Peace River district there is a
projection of the coal formations described for Alberta. Tertiary
lignites also occur on the Liard and Taku rivers but the deposits are
little known.

The coal seams of Vancouver Island are of Upper Cretaceous age,
according to C. H. Clapp, and they occur in the Nanaimo series which
is supposed to be largely estuarine in origin and is about 10,000 feet
thick. The topographic conditions during its formation were not
uniform and the beds in many cases lack persistency. The series has
in places been greatly folded and faulted. The coal is of bituminous
quality. There are six main basins as follows: Quatsino Sound at
the northern end of the island; Suquash on the east coast; Comox,
Nanaimo and Cowichan, all on the Strait of Georgia; and the Alberni
in the central part of the island. The Suquash, Comox and Nanaimo
basins contain seams which are being worked. In the Suquash

350 THE COAL FIELDS OF THE WORLD AMERICA

basin the beds are little disturbed and regular. The coal is a low
carbon, high moisture, bituminous coal. In the Comox basin the
lower seams lie over an irregular bottom and are quite irregular in
thickness and distribution. In some places the coal is broken and
coked by igneous intrusions. It is bituminous and coking and has
the highest fuel ratio of any of the Vancouver Island coals. In the
Nanaimo field there are many faults and the seams vary very greatly
in thickness and quality within short distances, but they are quite
persistent in extent. A case is cited by Clapp where a seam varies,
within 100 feet, from 2 feet of dirty slickensided coal to 30 feet of
clean coal. There are three seams with an aggregate of 10 feet of coal
which is a high-volatile, coking, bituminous variety. This basin
has produced the larger part of the coal of British Columbia.

The coals of the Queen Charlotte Islands are of two geological
ages Cretaceous and Tertiary, supposedly Miocene. The Creta-
ceous coals vary from high- volatile bituminous to semianthracite and
the Tertiary are subbituminous coals and lignites, some of the latter
of very woody types. Part of the Cretaceous coal is coking. The
semianthracite is unusually high in water and much of it is high in ash.
The main basin lies on the southern end of Graham Island where the
shales have been highly folded between masses of crystalline rocks.
In some places the coal is greatly crushed. The Tertiary coals are
not of much importance.

Yukon Territory. Coal has been mined at five points in the
Yukon: Tantalus Mine, and Five Fingers Mine on the Yukon River;
on Cliff Creek; on Coal Creek, a tributary of the Yukon; and on Coal
Creek, a tributary of Rock Creek. According to the conclusions of D.
D. Cairnes, the coals are Jura-Cretaceous and Tertiary in age. The
Tertiary coals are upper Eocene and they are lignites with con-
siderable resin. In places volcanic rocks are associated with
the soft shales and clays and loosely cemented conglomerates and
sandstones.

There are two coal horizons in the Jura-Cretaceous rocks, the upper
being the Tantalus conglomerates, about 1000 feet thick, and the
lower the Laberge series about 3800 feet in thickness. The coal
seams occur near the top of the latter series which consists of arkoses,
graywackes, sandstones, tuffs, shales and slates. The coal is bitumi-
nous and in most places non-coking. The coal of the lower seam

THE ARCTIC ISLANDS

351

when washed produces commercial coke. Some semianthracite occurs
in the Whitehorse area.

Northwest Territories. There are several coal basins in this
region. One of these in Tertiary rocks, occurs in the Mackenzie
River valley and runs a short distance up the Bear River at Fort Nor-
man. There is probably a lignite area running south up the valley
of the Mackenzie from Fort Norman and an area around the north-
west side of Great Bear Lake. Three seams have been reported with
a maximum of about 16 feet of coal.

FIG. 115. The Tantalus coal mine on the Yukon River. (Photo by E. S. Moore.)

Along the Peel and Horton rivers in the vicinity of the Mackenzie
delta there are Cretaceous rocks carrying thin seams of coal with a
maximum thickness of 4 feet. Some of the seams have been on fire
in the past, producing reddened outcrops which offer striking features
to the traveler. So far as known all the coal in the Territories is
lignite.

The Arctic Islands. Very little accurate information regarding
the coal deposits on the Arctic Islands has been obtained but it is
known that coal occurs at two horizons, in the Tertiary and in the
Lower Carboniferous. The Tertiary coals are lignites and the older

352 COAL FIELDS OF THE WORLD AMERICA

coals are bituminous. It is estimated that some 6000 square miles
on Banks Island and the Parry Islands is underlain with Lower
Carboniferous coals. Only one seam has been found but it is said
to reach a maximum of 50 feet in thickness. Small deposits of Ter-
tiary coal are believed to exist on Ellsmere, Baffin and Bylot islands.
On Ellsmere Island a seam of Tertiary coal 25 feet thick has been
reported from Cape Murchison. Cannel coal and oil shale have been
found on the Parry Islands.

NEWFOUNDLAND

Owing to the prominence of the large and well developed coal
deposits in Nova Scotia little attention has been paid to the Newfound-
land deposits which are not so extensive nor so readily mined as those
in Canada. There are, however, at least two areas of Carboniferous
rocks which carry considerable coal in Newfoundland. One area
is on St. George Bay and the other is about 100 miles northeast of it
in the Humber River valley. In the former area there are, according
to J. P. Howley, as many as nine seams varying in thickness from
i foot to 9 feet. The beds are greatly disturbed and many of the
seams are of small extent.

In the Humber River valley the strata are for the most part older
than the Pennsylvanian and they carry oil shales and material re-
sembling the albertite of New Brunswick. There are, however, in
parts of the district small areas of the Coal Measures which carry
several workable seams running up to about 6 feet in thickness and
some of the seams are greatly folded although in much of this field
the strata are nearly flat. The Newfoundland coals are bituminous
to semibituminous in character.

COAL DEPOSITS or THE UNITED STATES

PRODUCTION

The United States not only has the largest deposits of coal of any
country in the world but she is also developing them at a more rapid
rate than any other country. A preceding table (page 335) shows
the relative production of the countries of the world and the following
table indicates the rank of the various states of the Union in pro-
duction and the value of the coal produced. Pennsylvania has long
been the chief producer in the country.

o *

H S 1

Gfl

>. 1?

PRODUCTION

,S <8 %& 3 "8 3 i

$> f IH M CO 00 W -* C

353

O M ^^ M O VO OO t^t^vo IO O> IO 10 t^- O

VO O^OO TfCTiM ^VO (N IO*H IOM O^^O

vo fO "^ 04 c^ovo Civo Tj-f-oS^^roo fO

(C C C* M" VO* O* M* ^f fO 00* t> M* O* N

M VO^NMVOM M OM

III P$|

ofoc*t--oo*o"iio** >

v5oOM*^&r*5vooo
^- M M 10 Oi M

II - *

^^ S'g s^sa

oot^

8 R

MM lOVOtOOPOMNOl

00 Jo "M ** N

f~ (~0 N ro

t^ N Ol

cfi ^ M T? ro ro

354

THE COAL FIELDS OF THE WORLD AMERICA

CO
p

Q S

o s

249,272,837
283,650,723

10 00

I I

502,519,682
87.578,493

2"S

10 c ro oo

1 I
I I

co oo"

ft!

S 3

Total bitumi
Pennsylvania
anthracite ..

C8 ^

ill

|3l

-.11

o Cali
b) Inclu
Mineral

BITUMINOUS AND ANTHRACITE COAL
A Indicates anthracite coal Q coking coal

Areas

containing workable
coal beds

Areas that may Areas probably containing

contain umrkable Workable coal beds under

coal beds such heauy cover as not

to be qvailable at present

Areas

containing workath
coal beds

PLATE XII. Map of the coal-fields of the United States (U. S. Geol. Survey.

UBBITUMINOUS COAL

UiGNITE

Areas that may Areas probably containing

contain workable workable coal beds under

coal beds such heavy cover as not

to be available at present

I I I I

Areas Areas that may

containing workaSEe contain workable

lignite beds lignite beds

nted by permission from Rles 1 Economic Geology, published by John Wiley & Sons, Inc.)

DISTRIBUTION BY KINDS OF COAL 355

DISTRIBUTION BY KINDS OF COAL

The Geological Survey has adopted, according to M. R. Campbell,
the following divisions in classifying the coal areas of the country,
(Plate XII): (i) Coal province (2) Coal region (3) Coal field (4)
Coal district. The following provinces have been recognized: (i)
Eastern province; (2) Interior province; (3) Gulf province; (4)
Northern Great Plains province; (5) Rocky Mountain province;
and (6) Pacific Coast province. These provinces are subdivided into
regions as follows: The Eastern province is divided into (a) The
Anthracite region of Pennsylvania; (b) The Atlantic Coast region,
including the Triassic fields of Virginia and North Carolina; (c) The
Appalachian region extending from northern Pennsylvania into
Alabama and embracing also parts of Ohio, Maryland, Virginia, West
Virginia, Eastern Kentucky, Tennessee and Georgia. The Interior
province is divided into (a) the Northern region, containing only the
coal field of Michigan; (b) The Eastern region including the fields
of Illinois, Indiana and Western Kentucky; (c) The Western region
including the coal fields of Iowa, Missouri, Nebraska, Kansas, Ar-
kansas and Oklahoma and (d) The Southwestern region, in Texas.
The Gulf province includes (a) The Mississippian region, in the
east and (b) The Texas region to the west. The former includes the
states of Louisiana, Mississippi and Alabama and the latter Arkansas
and Texas.

The Northern Great Plains province includes (a) The Fort Union
region with the lignite fields of North Dakota, South Dakota, eastern
Montana and the subbituminous field of northeastern Wyoming;
(b) The Black Hills region of Wyoming; (c) The Assinniboine region
in Montana; (d) The Judith Basin region in Montana; (e) The
Denver region in Colorado; and (/) the Raton Mountain region of
Colorado and New Mexico.

The Rocky Mountain province is not clearly separated from the
Great Plains province. It includes (a) The Yellowstone region of
Montana; (b) The Bighorn Basin region of Wyoming; (c) The Hams
Fork region of western Wyoming; (d) The Green River region of
southern Wyoming; (e) The Uinta region of Utah and Colorado;
(/) The San Juan River region of Colorado and New Mexico; and
(g) The southwestern Utah region.
The Pacific Coast province is not divided into regions. It em-

356 THE COAL FIELDS OF THE WORLD AMERICA

braces coal fields in Calfornia, Oregon and Washington. It is the
smallest of the provinces.

The following table, prepared by Campbell for the Twelfth Inter-
national Geological Congress, presents the areas of the various prov-
inces, the types of coal in each, and the character of the coal. The
total production of each state to the end of 1917 has been added to
show the extent of exhaustion of the resources. The estimate in-
cludes all seams not less than 14 inches thick and not more than
3000 feet below the surface. A detailed description of the classes of
coal mentioned in this table is found in Chapter V under Classifi-
cation of Coals.

The total estimated tonnage of all kinds of coal for the United States
above 3000 feet in depth is 3,225,394,300,000 metric tons or about
one-tenth more in short tons. The amount produced up to the
end of 1917 was 12,130,805,450 short tons. By adding approxi-
mately 50 per cent of this amount for waste in mining and other
operations the total coal exhausted is approximately 18,196,203,175
short tons. This is almost negligible compared with the coal re-
sources of the country, being slightly more than one-half of one per
cent, but in many fields the output represents the best coal from the
most accessible seams.

bo II

'C c

H.2

DISTRIBUTION BY KINDS OF COAL

gftggJJ-fc ..^oo I

357

Coal below
surface from
3000 to 6000
feet

Anthracite
and Semi-
anthracite
al (Class A

emibitu
ous coal
i Class

Subbitumi-
ous coal (No.
i Class D)

IS !f

O O O lO O O OOOOOl^ 1000 O

ooo^oioor* looiO'OO'O ^0*0

^'CSO'^'OO* IOCS*-* TfM COCSC^

* 8

g &

l-a

358

THE COAL FIELDS OF THE WORLD AMERICA

Illl

m S"

S 8

00 M

i t
i si i

CT> N ro CO M

n.
id

Gulf
Arka
Texas

- . ->..-e

eld
e r

Rocky
Montana:
N. F. Fla
field
Mountain fi
Yellowstone
Red Lodge

uc-
al
917

Total
tion
o end

DISTRIBUTION BY KINDS OF COAL

I ^

oo* rt

3 J

359

001
327
,153

o o

T QJ .fa <

Anthraci
and Semi
thracit

8 o_
* "

ibitum
s coal
No i
ass B)

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Province
tate and Field

^<o T)T! '^ G .S C ! I i'O'S

1 22 li l 1 iiS-jl*

Coas
ingto

gon
ifor

Pacific
Wash
Oreg
Calif

360 THE COAL FIELDS OF THE WORLD AMERICA

GEOLOGICAL AGE OF THE COAL-BEARING FORMATIONS

As indicated in the table (page 338) the coal seams of the United
States range from Lower Carboniferous (Mississippian) to Miocene
in age. The eastern part of the country in a general way may be said
to carry the Carboniferous, Permian and Triassic coals and the west-
ern and Gulf regions the Cretaceous and Tertiary coals. In a gen-
eral way it may be said also that the coals of the east are of higher
grade than those of the west because all the lignite and most of the
subbituminous coal lies in the western part of the country or around
the Gulf of Mexico. The Carboniferous system is the great coal pro-
ducer of the east because at the beginning of that period large areas
in the eastern part of the continent had but recently emerged from
beneath the sea. There were excellent conditions for the develop-
ment of great swamps on the then existing low lands as there are
along the coasts of Virginia and North Carolina today. The west-
ern part of the continent was still largely under the sea at that time
and there is almost no Carboniferous coal in that part of the country.
The age of the coal does not necessarily determine its quality, but,
other things being equal, the older the coal usually the higher
the fixed carbon because it has been longer subjected to pressure.
There is much excellent coal in the West where the younger forma-
tions have been sufficiently squeezed to devolatilize it.
The geological age of the coal according to provinces is as follows:
(a) Eastern province. Semianthracite occurs in the Pocono of
the Mississippian in Virginia, in two small basins southeast of the
main field, in Frederick, Pulaski and Montgomery counties. The
other coals of the Eastern province all occur in the Pennsylvanian,
or Upper Carboniferous, except those in the Atlantic Coast region and
a few seams in the Permian. The coals in the Pennsylvanian run
through the Pottsville, Allegheny, Conemaugh and Monongahela
series. In the southeastern portions of the Appalachian region the
coals are to quite a large extent of Pottsville age. For example,
those of the famous Pocahontas field of Virginia and West Virginia
are of lower Pottsville, those of the New River field of lower and
middle Pottsville and much of the coal of Alabama and Georgia is of
Pottsville age. This formation carries some coal throughout the
whole Appalachian region but outside of the districts mentioned it
is, as a rule, not an important producer. The other formations,

GEOLOGICAL AGE OF THE COAL-BEARING FORMATIONS 361

especially the Allegheny and Monongahela, carry important coals
throughout the region with the exception that the latter formation is
not important in the southern part of the field. The Permian car-
ries coal in Pennsylvania, Ohio and Maryland. In the Atlantic
Coast region of Virginia and North Carolina the coal is Triassic in
age, this being the only coal of that age in the country.

(b) Interior province. The coals are all Pennsylvanian, the most
widespread formations being the Pottsville and the Allegheny.

(d) Northern Great Plains province. The coals in this province
range from the Kootenay of the Lower Cretaceous, around the Black
Hills, to the Fort Union of the Eocene, in which the bulk of the
lignite occurs. There is much difference of opinion among geologists
as to whether most of the coal occurs in the Cretaceous or in the
Tertiary as the dividing line between the two systems is in many places
not distinct. In the Dakotas all the important coal seams, which are
almost entirely lignite, are of Eocene age, but there is a little coal in
the Lance formation of the Upper Cretaceous. In Montana the coal
runs from Jurassic through Lower Cretaceous and Upper Cretaceous
to Eocene, very little of it being Jurassic. The Wyoming coals are
Lower and Upper Cretaceous and Eocene and those of Colorado are
mostly in the Montana series of the Upper Cretaceous with important
beds in the Laramie and a little in the Dakota series. Those of New
Mexico are also of Upper Cretaceous, (Montana) age with the excep-
tion of a very small area of lower Pennsylvanian.

(e) The Rocky Mountain province carries coals from Lower Cret-
aceous to Miocene in age. In addition to the states mentioned under
the Northern Great Plains province, Arizona contains Upper Cret-
aceous coals; those of Utah are mostly in the Montana and Colorado
series of the Upper Cretaceous, and some lignite occurs in the Eocene.
In Idaho the coal is of Upper Cretaceous and Eocene ages.

(/) In the Pacific Coast province the coals are chiefly Eocene in
age but small areas are Miocene.

(362)

PLATE XIV. Structure section through the Mahi

and Shenandoah basins. (By courtesy of J. Bevan.)

PENNSYLVANIA 363

THE COAL FIELDS OF THE VARIOUS STATES 1

Eastern Province

Pennsylvania. 2 Pennsylvania contains the anthracite region in
the east and the bituminous fields in the west and north-central parts
of the state. These two areas were originally connected but they have
been separated by erosion. The strata in the bituminous fields are
as a rule but slightly folded and the faults, although numerous in
some districts, are not of great throw, while in the anthracite region
the strata are characteristically highly folded and there are extensive
thrust faults which complicate the mining operations. There are
some anthracite beds which lie practically flat for considerable dis-
tances. Such are, for example, some of those in the Northern basin
around Scranton and Wilkes-Barre. These have, nevertheless, been
subjected to great pressure but the strata have resisted buckling and
the pressure has been transmitted to the coal seam changing the coal
to anthracite.

Anthracite region: In the anthracite region the coal lies almost
entirely in the synclines as it has been protected from erosion by the
Pottsville conglomerate, or as it is often called, Millstone grit, and the
Pocono sandstones. These formations are brought up in the anticlines
between the basins and between these formations the red Mauch
Chunk shale and sandstone makes a distinct horizon-marker and
indicates the lower limit of all coal. Usually the Pottsville conglom-
erate marks the base but a few seams have been found in it. Some
of the synclines are probably of great depth; over 4000 feet, in the
Southern field. Mining has not so far been carried beyond 2200 feet,
with the deepest shaft only 1850 feet, but it must be in the future.
The region is usually divided into the Northern, Eastern-middle,
Southern and Western-middle fields and these fields contain the
following districts. The Northern includes Carbondale, Scranton,
Pittston, Wilkes-Barre, Plymouth, Kingston and Nanticoke, these
making up the Wyoming trade region. The Eastern-middle field in-

1 For special comprehensive reports see: 22nd Annual Report, U. S. Geol. Survey,
Part III, 1902; The Coal Catalog, E. N. Zern, Editor, Keystone Consolidated Publishing
Co., Pittsburgh, 1918; The Coal Fields of the United States, with map, by M. R. Campbell,
U. S. Geol. Survey; Coal, by E. W. Parker, Mineral Resources of the United States, 1910.

2 Second Geological Survey of Pennsylvania; County Reports and Geologic and
Topographic Survey Commission reports. Also 22nd Annual Report, U. S. Geol. Survey,
The Pennsylvania Anthracite Coal Field by H. H. Stoek.

364 THE COAL FIELDS OF THE WORLD AMERICA

eludes the Green Mountain, Black Creek, Hazleton, Beaver Meadow,
and Panther Creek districts, these making up the Lehigh trade region.
The Southern field includes the East Schuylkill, West Schuylkill,
Lorberry and Lykens Valley districts, while the Western-middle field
embraces the local districts of East Mahanoy, West Mahanoy and
Shamokin. The last two fields are comprised in the Schuylkill trade
region.

The structure of the region is illustrated by the accompanying sec-
tions (Pis. XIII and XIV) and the names of the seams and their
relations to one another are also indicated. The anticlines lie in a
general direction of about N. 70 E. and as a rule the folds are steeper
on the northwestern side of the anticline than on the opposite side
since the thrusts producing them came from the southeast. The
thickest seam is the Mammoth which reaches 50 to 60 feet of com-
paratively clean coal and in some places is doubled by folding so that
over 100 feet of coal occurs in a stripping. Since the cover over this
and some of the other seams is so thin much coal is mined by stripping
off the cover and digging the coal with steam shovels. The depth of
the cover removed varies from almost nothing to 90 feet, although one
stripping will reach almost 200 feet in depth under exceptional
conditions. This is at Locust Mountain.

The best-known seams in the various fields are as follows: In the
Southern field there are the six Lykens Valley seams in the Potts-
ville conglomerate, No. VI being the lowest, and three of these beds
are found also in the Western-middle field. They vary from thin un-
workable seams up to about n feet in the Western-middle field.
There are no workable seams in the Pottsville in the other two fields.

The lowest bed in the Coal Measures proper is the Buck Mountain
bed of the Southern, the Western-middle and Eastern-middle fields.
This bed is thickest in the Western-middle field and it probably
corresponds to the lowest split of the lowest Red Ash bed in the
Northern field. It runs between 3 and 19 feet in thickness. Be-
tween the Buck Mountain and Mammoth seams in the Southern
field there is the Skidmore bed; in the Western-middle field there
are the Seven-foot and Skidmore beds and in the Eastern-middle
field the Gamma bed, the Wharton bed and the Parlor bed.

In the Northern field the lowest workable beds are the three Red
Ash or Dunmore beds, also known as the Powder Mill and Clifford

PENNSYLVANIA 365

beds. Above the Dunmore beds lie the Ross or Clark seam, and the
Twin beds, followed by the two splits of the seam known as the
Mammoth in the other fields. In this field this seam is known as
the Baltimore, Pittston, Fourteen-foot, Big Bed or Grassy Island bed.
Above this big seam lie the Rock bed and the Diamond bed, each
about 3 feet thick, followed by the Hillman or Olyphant No. I, running
up to about 15 feet in thickness. Above this seam is the Kidney,
Diamond or Olyphant No. II which probably corresponds to the
Diamond beds of the southern fields. It is about 5 feet thick in this
field. The Abbott and Snake Island beds lie above it.

In the Eastern-middle field the Mammoth bed which is here
around 58 feet thick is the highest bed of importance and it is stripped
a great deal. In the Western-middle field there are the Holmes
bed, the Primrose bed, the Orchard beds, the Diamond beds and
the Tracy beds, lying above the Mammoth seam which is here
about 60 feet thick.

In the Southern field the Mammoth seam has a number of splits
making up a total of about 1 20 feet of coal and partings. The seams
lying above the Mammoth bed are practically the same as those
just mentioned for the Western-middle field with the addition of the
Clinton beds. About twenty different beds have been worked in
this field.

It has been estimated that over 80 per cent of the coal in the Wy-
oming basin and approximately 75 per cent of that in the other
fields is marketable. The Pennsylvanian rocks are very thick in
the Southern field, the Pottsville conglomerate varying from noo to
1475 feet in thickness and the other formations making up 2500 feet
more. In the Western-middle field about 1200 feet of measures
remains, and in the Northern field a maximum of 2200 feet is found
in the deep basin between Nanticoke and Wilkes-Barre. The aver-
age thickness for the Pottsville conglomerate and the Coal Measures
respectively, in the various fields is placed at the following figures:
Northern field 225 and 1800 feet; Western-middle 850 and 1000
feet; Eastern-middle 300 and 700 feet, and Southern 1200 and 2500
feet.

An interesting feature in the Northern field is the buried valley
between Pittston and Nanticoke in which a large stream flowed
before the glacier passed over the region. When the glacier pushed

03 a

nojnosq;

< 3

(366)

PENNSYLVANIA

367

across the valley in the Pleistocene epoch the valley was filled up
and since the glacier melted away the Susquehanna River has made a
new channel for itself. It has also been suggested that this valley
may have been caused by glacial erosion. Since this pre-glacial
valley is filled with debris which holds much more water than the
solid rock, it is naturally a menace in mining operations and it has
been pretty carefully mapped out.

300-

Homewood Sandstone

Upper Mercer Coal

20- -ZJ^I^I Lower Mercer Coal

200-

100-

> Conoqueneasing

Sharon Coal

Sharon Conglomerate

FIG. 117. Section of the Pottsville
in Mercer County, Pa. (After I. C.
White, U. S. Geol. Survey.)

Upper Free port Coal (E)

Lower Freeport Coal ( D )

Freeport Sandstone

Upper Kittanning Coal (C')
Johnstown Cement

Middle Kittanning Coal (C)

Lower Kittanning Coal ( B)

Ferriferous Limestone
Clarion Coal (A')

BrookvilleCoal(A)

FIG. 118. Columnar section through
the Allegheny formation on the Alle-
gheny River, Armstrong County, Pa.
(After D. White, U. S. Geol. Survey.)

Pennsylvania produces almost all the anthracite mined con-
siderably over 99 per cent in the country. Anthracite was dis-
covered by the earliest settlers about 1762 and used by smiths and
for local purposes for a number of years before active mining began.
The records of shipments begin about 1805, but coal is said to have
been shipped during the Revolutionary War. At first the people
in the towns would have nothing to do with it as they were skep-
tical regarding its value as a fuel.

The Bernice field of Sullivan County is regarded by some as part of

3 68

Feetr

ittle Pittsburgh Coal

Connellsville Sandstone

Morgantown Sandstone

11 -.T-_rJ "Elk Lick Coal

Crinoidal Coal

100-

THE COAL FIELDS OF THE WORLD AMERICA

the anthracite region and the coal is put
on the market as anthracite although it
is more strictly semianthracite. It marks
the transition from the anthracite region
to the bituminous fields farther west.

Bituminous region: 1 The bituminous
fields of the state cover 14,200 square
miles and while the southeastern border
of the area has suffered a good deal of
compression where the intensive folding
found farther east dies out, the beds for
the most part have gentle dips and the
coal occurs in a large number of roughly
parallel synclinal basins. The Broad top
field in Huntingdon and Bedford counties
is a remnant of the Coal Measures folded
down into the mountains in that lo-
cality and it is more disturbed than most
of the other bituminous fields. Owing
to the greater amount of folding which
the eastern portion of the bituminous
area has suffered, much of the coal is
semibituminous in character and the
Clearfield district is noted for its " Smoke-
less coal " of this variety.

The coals occur chiefly in the Alle-
gheny and Monongahela series of the
Coal Measures, between 40 and 50 per
cent of the coal mined coming from the
former series. The Pottsville (Fig. 117)
contains the Sharon and Mercer coals
mined in restricted areas. The Allegheny
(Fig. 1 1 8) is about 300 feet thick on the
average and contains the Brookville, or

1 White, D., and Campbell, M. R., The bitumi-
nous coal fields of Pennsylvania. 22nd Annual Rept.
U. S. Geol. Survey, Pt. Ill, 1902. Also White,
U. S. Geol. Survey, Bull. 65.

Bakerstown Coal

,Masontown Coal

Mahoning

FIG. 119 Columnar section
through the Conemaugh forma-
tion on Dunbar Creek, Fayette
County, Pa. (After I. C.
White, U. S. Geol. Survey.)

PENNSYLVANIA

3 6 9

Waynesburg Coal

300-

200-

Uniontown Coal

100-

Sewickley Coal

A coal, the Clarion or A 1 , the Lower Kit tanning or B, the Middle
Kittanning or C, the Upper Kittanning or C 1 , the Lower Freeport
or D and the Upper Freeport or E. The Brookville coal is
worked in many places in the eastern counties of the bituminous
fields and the Clarion coal is of workable thickness in numerous lo-
calities. The Lower Kittanning is usually Feet
less than 4 feet thick but it is uniform in
distribution and character. It is also known
as the Miller seam. It is a valuable coal
in at least eleven counties. The Upper
Kittanning is characterized by a large
amount of cannel coal in Beaver and Clear-
field counties. The Middle Kittanning is
not relatively important as it is thin and
in many places dirty. The Upper and
Lower seams are well known for coking,
domestic, gas-producing and other pur-
poses. The lower Freeport or Moshannon
seam is a well-known seam, especially in
Clearfield, Jefferson, Indiana, Cambria and
Center counties. This coal is adapted to
almost all varieties of uses. The Upper
Freeport extends over a large area but it
varies greatly in thickness and quality.

The Conemaugh series (Fig. 119) carries
several seams such as the Berlin, Bakers-
town and Coleman but they are compara-
tively unimportant.

The Monongahela series (Fig. 120) con-
tains the famous Pittsburgh seam and the
Redstone, Sewickley and Waynesburg seams. The former seam
occurs in the southwestern portion of the state in Greene,
Washington, Westmoreland, Fayette, Allegheny, Somerset and In-
diana counties. It runs from 4 to 9 feet in thickness and averages
about 7 feet over an area of between 2000 and 2500 square miles.
The coal of this seam is excellent for a great variety of uses. It has
been the famous coking coal of the Connellsville district, and West-
moreland County furnishes one of the best of gas coals from this seam.

..Redstone Coal

Pittsburgh Coal

FIG. 1 20. Columnar section
of the Monongahela forma-
tion in Fayette County, Pa.
(After Stevenson, U. S. Geol.
Survey.)

370

THE COAL FIELDS OF THE WORLD AMERICA

The Redstone seam is about 3 J feet thick. It is mined in a number
of places in the southwestern counties, but on the whole it is not very

important. The Waynesburg seam is
mined in Westmoreland, Washington and
Greene counties. It is about 3 feet thick
on the average but locally it runs 6 feet,
and in places it is a block coal. The coal
is frequently bony.

The Dunkard series of the Permian
system carries the Washington seam which
is worked to some extent in Washington
and Greene Counties. It may reach 10
feet in thickness but, like the Waynesburg
seam, it carries much rock.

Rhode Island. 1 The coal in this state
is interesting chiefly because of the fact
that it has been so squeezed and broken that
some of it has been turned into graphite,
and therefore does not burn. The propor-
tion of fixed carbon is so high compared
with the volatile matter that combustion
will not take place in some of the coal. The
coal is also very high in ash, much of it
running 30 per cent or more. It has been
mined intermittently.

Ohio. 2 Many of the seams mined in
southwestern Pennsylvania continue into
Ohio. They are all bituminous. In the
Pottsville formation (Fig. 122) there are in
ascending order, Sharon, or No. i, the
block coal; Quakertown or No. 2; and

ru, ^"olumnar section Lower Mercer or No. 3. Of these the
through the Dunkard forma- Sharon, which is about 3 feet thick, is the

tion in Greene County, Pa. on }y one o f mu ch importance although the
(After Stevenson, U.S. Geol. m j ned ^ certa ; n ^ The

Survey.)

Sharon has been mined in limited areas, as

1 Ashley, G. H., Rhode Island Coal. U. S. Geol. Survey, Bull. 615, 1915.

2 Bownocker, J. A., The coal fields of Ohio, with map. U. S. Geol. Survey, Prof.
Paper loo-B, 1917. Also, Bull. 9, Fourth series, Ohio Geol. Survey, 1908.

OHIO 371

around Massillon and Jackson. This coal is largely exhausted.
It is characterized by coatings of calcium carbonate on the joints,
known as " white cap." The sulphur is very low and the coal has
been used raw in the blast furnaces in making pig iron. The
Quakertown bed, also known as the Wellston or Jackson Hill bed,
supplies good coal for domestic and steam purposes, and in Jackson
County where it is mined most it runs about 4 feet in thickness.
The Lower Mercer, or No. 3 and the Upper Mercer or No. 30, are
unimportant. They are characterized by lying und^ thin lime-
stones which go by the same name. The Upper Mercer is also
known as the Bedford cannel and in Coshocton County it reaches a
thickness of about 9 feet of which 5 feet is cannel.

The Allegheny series contains the most widely extended and best
beds of the state. The seams in ascending order are the Brookville
or No. 4, the Clarion or No. 40, the Lower Kittanning or No. 5, the
Middle Kittanning or No. 6, the Lower Freeport or No. 6a and the
Upper Freeport or No. 7. The Brookville seam runs from 2 to 4 feet
in thickness and it is not extensively mined as it is impure and thin
over large areas. The Clarion bed lies under the Vanport, or Ferrif-
erous limestone, which is a good horizon-marker. It is of compara-
tively little value. The Lower Kittanning is not of great impor-
tance but it is mined and a very important bed of clay lies beneath it.
The Middle Kittanning is regarded as one of the most important in
Ohio. It usually runs around 3 to 4 feet in thickness; it is high in
sulphur in many places but is widely extended. In the Hocking
Valley field what is known as the Jumbo " fault " causes much diffi-
culty in mining. It is not a fault but an old " cut-out " where a
stream has washed away the vegetal matter and deposited sand and
mud in its place. The Lower Freeport is of little commercial im-
portance except around Steubenville, while the Upper Freeport is a
very important seam. The coal breaks down readily and is not
suitable for transportation but it is a good steaming fuel. Its maxi-
mum thickness is about 7 feet. Lying between the Upper Freeport
and the Pittsburgh bed is the Conemaugh series, about 350 to 500
feet thick. It contains the Mahoning, Mason and Anderson seams,
the latter being equivalent to the Bakerstown of Pennsylvania, but
they are thin and little worked.

The Monongahela, or Upper Productive Measures, contains three

372 THE COAL FIELDS OF THE WORLD AMERICA

seams of importance: The Pittsburgh or No. 8 at the base; the Red-
stone or Pomeroy, or No. 8a; and Meigs or No. 9. The Pittsburgh
is not as extensive or of as good quality as the Middle Kit tanning. It
occurs in the three fields, Belmont County, Federal Creek and Swan
Creek. The coal is used mostly for steam and domestic purposes.
It runs about 6 feet in thickness with several clay partings in many
places, and thin limestones occur in the shales of the roof. In some
areas, as in Jefferson County, the coal is mined with steam shovels.
The Pomeroy was for years regarded as the Pittsburgh bed of Penn-
sylvania but it is now known to be the equivalent of the Redstone.
It runs from 2 to 5 feet in thickness and is high in ash. The Meigs
Creek is an important bed but in many places it is irregular. It is
the equivalent of the Sewickley seam of Pennsylvania. The coal is
used mostly for steam and domestic purposes. It is like many of
the Ohio coals in being high in sulphur, and bands of pyrite frequently
occur. In the Dunkard group of the Permian there are several thin
seams but they are not of importance.

Maryland. 1 The coals of Maryland occur in the following five
basins: Georges Creek, Upper Potomac, Castleman, Upper Youghio-
gheny and Lower Youghiogheny, all confined to Allegheny and
Garrett counties. The Georges Creek basin is the most prominent
producer with most of the remaining coal coming from the Potomac
basin. The coals are mostly semibituminous. The following seams
are recognized: Brookville, Clarion, Lower Kittanning, Upper Kittan-
ning, Lower Freeport and Upper Freeport, in the Allegheny series.
Those of the Pottsville are unimportant. In the Conemaugh the
Bakerstown seam occurs and is of some importance. The Mononga-
hela carries the Pittsburgh seam and the Upper Sewickley, also known
as the Gas coal. The Pittsburgh seam or " Big Vein " has been the
main source of the coal of the state but the other seams are being devel-
oped more and more in recent years. This seam runs about 8 feet
in thickness although in the southern part of the field it reaches 14
feet. The coal is massive and breaks down in large blocks. It fur-
nishes a famous bunkering and steaming coal and can be coked, but
it is not used to any extent for the latter purpose.

West Virginia. 2 Many of the coal seams of Pennsylvania, Ohio

1 Clark, W. B., Maryland Geol. Survey, Vol. V, 1905.

* White, West Virginia Geol. Survey, Vol. II, 1903 and Bull. 2, 1911.

Shale

Coal No. 7 a
Fire clay

Sandstone andjshale |5si5

Coal No. 7
Fire clay
Limestone

Gray shale

Buff limestone
Black band iron ore
Fire clay
Limestone
Coal No, 6 b

Shale and limestone

Coal No. 6 i
Fire clay

E2~==J 0-50

0-50

Gray or black shale |=f=^E-=| 5-50

Coal No. 6
Fire clay
Limestone

Gray or black shale |EE:^=|

Coal No. 5
Fire clay

Shale and sandstone fe~t

Limestone
Coal

Fire clay
Sandstone
Coal No. 4

Shale and sandstone

Coal No. 3 b
Shale and sandstone
Coal No. 3 a
Limestone with iron oi

Fire clay 5-15

Shale and sandstone

Coal No. 2
Fire clay

Shale

Sandstone

Gray shale

Coal No. 1
Fire clay

Conglomerate

540

Grof.

Stripe vein
Brush Creek

Mahoning

f Upper Freeport
I Cambridge
] Big Vein
I Waterloo

StillwelHoften
conglomerate)

Lower Freeport
Hatcher
Steubenville
Whaa

Upper Ktttanniiig
(not mined.in
Ohio)

(Hocking Valley
Straitsville
Middle Kittanning
Sheridan

Mineral-Point
Lower Kittanning
Leetonia
New Castle

Gray ferriferous;
Putnam Hill.
Upper Clarion

Brookeville
f Homewood
\ Piedmont

Tionesta
( Bruce

\ Upper Mercer
( Lower Mercer
\ Flint Ridge canne

Upper Massillon

f Wellston
1 Quaker.tow.n

Lower Massillon

{Brier
Massil
Jacksc

Hill

Massillon
Jackson Shaft

STRATA

SECTION FEET

Limestone
Sandstone
Coal No. 13

Stwidstoiu* andLsh.a.1
CoalNoU2

Limestone

Black shale
Coal No. 8
Fire clay
Limestone

30-70

U-30

Shale and sandstone pE^^'S 110
t-t^l^&l

Shale

Crinoidal limestone

Shale

Coal NO. 7 b

Fire clay

Shale and. sandstone

Shale

Coal No. 7 a.

Fire clay

LOCAL NAME

Macksbure
Waynesburg

Meig Creek
Sewickley

Redstone in
Pennsylvania

Pittsburgh

Norwich
Patriot

f Grof.
< Stripe vein
Brush Creek*

FIG. 122. Columnar section of the Carboniferous formations in Ohio.
Hazeltine, U. S. Geol. Survey).

(After
(373)

374 THE COAL FIELDS OF THE WORLD AMERICA

and Maryland extend into West Virginia, the main one being the
Pittsburgh bed. This state is the second most important producer
in the Union and her production is increasing rapidly. The main
fields of West Virginia are the Fairmont or Clarksburg, the Piedmont
or Elk Garden in the northern part of the state, and the New River,
Kanawha and Pocahontas fields in the southern part. The Piedmont
field is a narrow field lying in the Potomac basin to the east of the
others and it carries semibituminous or " smokeless " coal in the
following well-known veins: Pittsburgh, or " Big Vein," Thomas,
or Upper Freeport, and Davis, probably Upper Kittanning. The
Pittsburgh seam reaches a thickness of n feet.

Much of the coal from West Virginia, especially in the southern part
of the state, occurs in the Pottsville formation and this formation
seems to increase in relative importance in the states to the south-
west. The seams in the Pottsville in ascending order are the famous
Pocahontas seams, Nos. 3, 4 and 6 of the Pocahontas field. Poca-
hontas No. 3, known as the Thick seam and lying at the base of the
Pottsville, reaches 12 feet in thickness though usually running around
6 feet. Pocahontas No. 4 also runs about 6 feet in thickness and
No. 6 is not mined to any great extent. It runs up to 5 feet in thick-
ness. The coal of this field is semibituminous, low in ash and sulphur
and therefore suitable for mixing with high volatile coals in by-product
ovens. It is a wonderful steam coal. In the New River field the
lower and middle Pottsville, known as the New River group, carry
the Fire Creek, Beckley, Welch, Sewell and laeger seams. Of these
the Sewell, varying from 2 to 5 feet, the Beckley about 4 feet and the
Fire Creek, 3 to 7 feet, are the most important and most largely mined
seams. The coal is semibituminous and coking. In the Kanawha
field the group of rocks named after the field is of Upper Pottsville
age. The seams are the Eagle, Powellton, Gas, Alma, Cedar Grove,
Chelton, Winifrede, Coalburg and Stockton. Of these the Eagle,
Gas, Cedar Grove, Coalburg and Stockton are important. Some of
these beds reach 1 2 feet in thickness. The Cedar Grove and Stockton
carry cannel and the Coalburg and Stockton are known as the splint
coals. The coal of the Kanawha field is bituminous to semibitumi-
nous. It is coking, some of it is excellent gas-producing coal, and in
general it is of high grade.

In the Allegheny series the Lower Kittanning, Lower Freeport and

VIRGINIA 375

Upper Freeport seams are found. The first seam is important in
three of the fields and reaches 7 feet in thickness. The Upper Free-
port is important in the northern part of the state, in places reaching
9 feet. These coals are good steaming and by-product coking coals,
used chiefly for mixing with other types. In the Conemaugh the
Bakerstown seam is worked to some extent in the Potomac basin.

In the Monongahela the Pittsburgh, the Redstone, Sewickley and
Waynesburg seams all occur in the northern fields only, the Pitts-
burgh in the Fairmont, Panhandle and Piedmont fields. The Pitts-
burgh seam averages 8 feet 6 inches, of which 7 feet are mined. It
is a lump coal, high in sulphur in places, but much used in beehive
coking where sulphur is low. It is a high grade bituminous steam-
ing and domestic fuel. The Sewickley is an important seam reach-
ing 10 feet in thickness. It is a good coal, containing much min-
eral charcoal. The Waynesburg is mined but little.

Virginia. 1 Virginia is said to have produced the first bituminous
coal in the United States, coal having been discovered in 1700, min-
ing begun in 1787 and shipments make in 1789. This coal occurs in
the Atlantic Coastal region in rocks of Triassic age and in a syn-
clinal basin much cut by faults and so intruded by igneous rocks that
in places- the coal has been changed to natural coke. The coal is
bituminous to semianthracite and some of it is of high grade. Some
seams are very thick, but mining conditions are bad and mining
has only been carried on intermittently. This field extends into
North Carolina.

The other fields of Virginia are the Pocahontas or Flat Top field, a
continuation of the field of the same name in West Virginia, and the
Big Stone Gap field which extends into Kentucky. In Frederick
County there is a small isolated field, and another in Pulaski and
Montgomery counties. In these fields the coal is of Mississippian age,
and in the Pocono formation. This is geologically the oldest coal in
the country. The coal is semianthracite to anthracite and of good
quality. It is mined when thick enough to work, and some seams
reach 4 feet or more in thickness.

1 U. S. Geol. Survey, igth Annual Kept., Pt. II, p. 393, 1898, Geology of the Rich-
mo,nd Basin, Virginia, by N. S. Shaler and J. B. Woodworth; also Bull, in, 1893, Geology
of the Big Stone Gap Coal Field of Virginia and Kentucky by M. R. Campbell; Mineral
Resources of Virginia by Watson, Bulls. 9 and 12.

376

THE COAL FIELDS OF THE WORLD AMERICA

FIG. 123. Outcrop of the "Big" seam at Pocahontas, Va. with crossbedded
sandstone above it. (Photo by H. Ries.)

FIG. 1 24. Breaker for semibituminous coal at the Merrimac Mine, Mef rimac, Va.

(Photo by H. Ries.)

KENTUCKY 377

The seams mined in the other fields are, in ascending order, the
Darby, Jawbone, Kennedy, Imboden, Lower Banner, Upper Banner
and Pocahontas No. 3. The Pocahontas No. 3 is a continuation of
this seam from West Virginia and here it is of the same quality and
averages about 9 feet thick. The other seams occur chiefly along
the extreme western part of the state. The Upper Banner and the
Imboden are very important and the latter is a specially good coking
coal. The other seams are all mined to a greater or less extent and
some of them run as high as 10 feet in thickness. They are Potts-
ville in age and of bituminous character.

Kentucky. 1 The coal fields of Kentucky occur along the south-
east and the northwest borders of the state, the southeastern portion
being included in the Eastern province and the northwestern in the
Interior province. The coal-bearing rocks of the southeastern part
of the state are Pottsville and Allegheny. The Pottsville is about
500 feet thick and carries a large number of coal beds. There are
about a dozen workable beds, the main ones being the Flag, Fire
Clay, Hazard, Keokee, Leonard, High Splint, Dean, Harlan, Miller's
Creek and Elkhorn. These seams range in thickness up to about 9
feet. The Keokee is equivalent to the Darby seam of Virginia.
The High Splint as the name indicates, carries splint coal, an im-
portant gas coal. The coals are bituminous. Some seams are good
coking and particularly good gas coals. There is a good deal of can-
nel coal in this field forming seams, or bands and lenses in the bitumi-
nous seams.

In the northwestern section of the state the main seams are known
as Nos. 9, ii and 12, of which No. 9 is equivalent to No. 5 of Illinois.
No. 9 is the most important producer. It averages about 5 feet in
thickness and lies within 300 feet of the surface. In places this seam
is badly faulted. No. 11, lying higher up, is more irregular but
thicker in places than No. 9, being about 6 feet thick. No. 12 is
worked in some areas. The coals are bituminous and higher in
volatile matter than those to the east. They are also high in sulphur
and ash.

1 Annual Kept., Inspector of Mines of Kentucky, 1902. Also Ky. Geol. Survey,
series 2, Pt. XI, Vol. IV, by Moore; and Bull. 18, 1912 by Fobs. For analyses see Ky.
Geol. Survey, New series, Chemical Reports.

378 THE COAL FIELDS OF THE WORLD AMERICA

Tennessee. 1 The Tennessee coal beds occur in the following
basins: Wartburg, Walden, Sewanee and Cumberland. In the
last-named it is said the Coal Measures are over 3000 feet thick and
that they contain almost 100 feet of coal. The Wartburg basin has
three or four beds which are now worked, one of which, the Brice-
ville, is about 4 feet thick. In the eastern part of the Walden basin
the beds are sharply upturned, but for the most part the coals of
Tennessee lie quite flat. The best known seams in the state are the
Sewanee, Jellico and Coal Creek. The coals are all bituminous and
most of them are suitable for steam, domestic purposes and gas manu-
facture. The Coal Creek coal is used in coking.

Georgia. 2 Only 167 square miles are underlain with coal in this
state and the coal is all of Pottsville age. The Walden basin of
Tennessee crosses through Georgia into the Warrior and Blount
Mountain basins of Alabama. The Lookout basin extends into
Walker County, Georgia. In this basin the coal is of high quality,
being semibituminous to semianthracite and low in sulphur. Part
of it is coked. The rest of the coal in the state is bituminous.

4000

FIG. 125. Structure section in the northern part of the Cahaba Coal Field, Ala.
(By Charles Butts, U. S. Geol. Survey.)

Alabama. 3 The Coal Measures in crossing from Georgia widen
out in Alabama and form four important basins, the Coosa, Ca-
haba, Warrior and Plateau basins. The Coosa basin is a deep syn-

1 Hayes, C. W., The Southern Appalachian Coal Field. U. S. Geol. Survey, 22nd
Annual Rept. Pt. Ill, p. 227, 1902. Also Resources of Tennessee I, No. 5, by Ashley.

2 McCallie, Georgia Geol. Survey, 1904.

3 Butts, C., The northern part of the Cahaba Coal Field, Ala. U. S. Geol. Survey,
Bull. 316, p. 76, 1907. Also reports by McCalley on the Warrior Field, 1900 and by
Gibson on the Coosa Field, Ala. Geol. Survey, 1895.

MICHIGAN

379

cline of unexplored depth about 60 miles long by 6 wide. It con-
tains a large number of seams. Two seams are worked, the Eureka
and the Coal City. This basin is considerably faulted and folded.

The Cahaba basin covers about 350 square miles and is very deep,
the coal beds probably extending more than 3000 feet below the sur-
face, (Fig. 125). The thickness of the Coal Measures is usually
considered about 5500 feet. There are about ten seams mined and
the coal is bituminous and coking.

The Warrior is the most important of the basins. The best known
seams are the Pratt and the Mary Lee as they furnish most of the
coal mined in the Birmingham district, and this coal furnishes the
coke after washing. The Pratt seam in places reaches 16 feet in
thickness. Besides these two seams 16 other beds are worked in
this basin. The Plateau field is small and undeveloped but it con-
tains many good beds. The coals in Alabama are all of Pottsville

age and bituminous in character.

T/tc Interior Province

Michigan. 1 The coal basin of Michigan contains a compara-
tively flat-lying, slightly faulted series which includes the Potts-
ville and Allegheny formations of the Pennsylvanian and which is

FIG. 126. Structure section in Bay County, Mich., from the Amelith Mine to the
Central and Michigan mines. It shows glacial drift overlying the eroded surface of
the Coal Measures. (After Lane, U. S. Geol. Survey.)

overlain by glacial drift. There are seven coal-bearing horizons of
significance and these are known as the Lower Coal, Lower Rider,
Saginaw, Middle Rider, Lower Verne, Upper Verne and Upper Rider.
The seams are very irregular in thickness and character and they
change rapidly from place to place (Fig. 126). The coal is of bitu-

1 Lane, A. C., The Northern Interior Coal Field. U. S. Geol. Survey, 22nd Annual
Report. Pt. Ill, p. 313, 1902. Also Geol. Survey, Michigan, Vol. VIII, Pt. 2.

300

100

Rallsford Shale
Red

Shaly Limestone

^\ Conglomerate

(380)

Sandy Shale
Conglomerate

Fie. 127. Columnar sections of the Coal Measures in Illinois.
(Illinois Geol. Survey.)

ILLINOIS 381

minous rank, is non-coking and dry and is used for steam, producer
gas, domestic, and related purposes.

Illinois. 1 Illinois has the largest area of Carboniferous coals of
any of the states as nearly three-fourths of the state is underlain by
Coal Measures. The basin is comparatively flat with from 1500
to 2000 feet of measures near the center. The seams are faulted in
many places by small faults and near the Kentucky border the beds
are caught in overturned folds and considerably faulted. The fields
are covered with glacial drift so that prospecting is often carried on
with difficulty, shafts being necessary to reach the coal. The shafts
in the state run from 25 feet to 1000 feet in depth but the majority
are probably less than 300 feet. The beds as a rule are extensive
and persistent. The coals are both coking and dry but the coals
which will coke are high in sulphur, the average running around 3
per cent for many of the mines, and they are therefore unsuitable for
commercial coke. They are used mostly for domestic, steam and
locomotive purposes. Much of the coal is washed and sized. The
longwall method of mining is used to a considerable extent in this
state.

In geological age the coals are Allegheny and Pottsville. The
most important seams are Nos. 2, 5, 6, and 7. No. i seam and a
few others occur in the Pottsville and are worked in the southern
part of the state, No. i probably corresponding to the Mercer
horizon farther east. No. 2 occurs in the Carbondale formation,
which is regarded as equivalent to the Allegheny, and is a very per-
sistent bed averaging around 4 feet in thickness. It is regarded by
some as equivalent to the Clarion coal of Ohio and Pennsylvania.
In places it contains many sulphur balls. These concretions are
also common in No. 5 and in the roof shale above that seam. No. 5
runs about 4 to 5 feet in thickness and is an important seam. No. 6,
or the "Belleville" seam, is probably the most persistent in the
state, and in the western part is mined to a depth of about 800 feet.
It runs from 5 to 6 feet in thickness over large areas and in places it
reaches 9 feet. No. 7 is mined around Danville and is from 5 to
7 feet in thickness. It contains much sulphur which can be read-

1 Ashley, G. H., The Eastern Interior Coal Field, U. S. Geol. Survey, 22nd Annual
Report, Pt. Ill, p. 271; Bulls, i to 15, 111. Coal Mining Investigations, at University
of Illinois, also Bulls. 4, 8 and 16, Illinois Geol. Survey.

382 THE COAL FIELDS OF THE WORLD AMERICA

ily separated by picking and washing. Another higher seam, No. 8,
is mined in some localities.

Indiana. 1 The coal beds of Indiana occur along the western
border of the state and the coal is all of bituminous rank. It occurs
in the Pottsville and Allegheny formations as in Illinois. Work-
able coal is found at eight horizons at least and six of these are
producing. The main seams are known as the Lower and Upper
Block, the Minshall, and seams Nos. 2, 3, 4, 5, 6, and 7. No. 8 is
thin. The lower coals, including the Block and Minshall seams,
are of Pottsville age and are characterized by being non-coking,
pure and dry coals which break into rectangular blocks. The seams
usually run about 3 feet in thickness as an average. The other
seams are classed as bituminous coals of Allegheny age and they
run from 3 to 10 feet in thickness with 5 feet a very common figure
and the beds very persistent. The shafts run from 50 to 450 feet
in depth for most of the field.

Iowa. 2 The coal fields lie in the southern and central part of the
state and cover about 12,500 square miles. The beds are of lower
Pennsylvanian age, as in Illinois and Indiana, and they occur in the
Pottsville and Allegheny formations. These are represented by

s.w.

FIG. 128." Ideal cross-section of the formations in Mahaska County, Iowa, illus-
trating the character of the Coal Measures in Iowa. (After H. Hinds, Iowa Geol.
Survey.)

two series of rocks, the lower, or Des Moines, and the upper, or
Missouri group. The Missouri group contains much limestone and
little coal, the Nodaway bed being the only one mined, and it fur-
nishes less than i per cent of the coal mined in the state. It is 16 to
20 inches thick and fairly persistent. The Des Moines group, al-
though consisting chiefly of shale and sandstone, has a thin lime-
stone bed near the middle. It carries a well-known seam, the Mystic
or Centreville bed, which is persistent and extends over into Mis-

1 Ashley, G. H., Stratigraphy and coal beds of Indiana Coal Field. U. S. Geol. Survey,
Bull. 381, p. 9, 1908; also Indiana Dept. of Geol. and Nat. Res., 33d Annual Rept. 1909.

2 Hinds, Henry, The coal deposits of Iowa. Iowa Geol. Survey, Vol. XIX, 1908.

MISSOURI 383

souri. The lower part of the Des Moines group carries a number of
beds and while they locally run up to 10 feet or more the average
is about 5 feet in thickness. The seams are characterized by their
lack of persistency and their sudden changes in quality. They lie
nearly flat and while faults are numerous they are not large. The
coal is dry, non-coking, comparatively high in sulphur and used al-
most entirely for domestic and railroad purposes. The coal field
is covered with glacial drift so that there are few outcrops and pros-
pecting is difficult. For this reason little is known about many of
the seams. Much of the coal lies 400 to 500 feet below the surface.

Missouri. 1 The same geological series occur in Missouri as in
Iowa, the Pennsylvanian rocks being divided into the upper, or Mis-
souri group and a lower, or Des Moines group. The upper is quite
largely a limestone series and carries little coal. Most of the seams
occur in the Des Moines group. Those near the base are very ir-
regular and lack persistency while the seams associated with the
thin limestone beds higher up in the group are very persistent and
comparatively regular. The main fields are the Bevier where the
Bevier seam is 3 to 6 feet thick; the Lexington with a seam 14 inches
to 2 feet thick which is mined by the longwall method; the South-
western field; the Novinger field with a seam 3^ feet thick and prob-
ably equivalent to the Bevier seam; the Marceline where a 29-inch
seam is mined; and the Mendota where the coal lies at about the same
horizon as that in the Lexington and the bed is supposed to be equiva-
lent to the Centreville seam of Iowa. It is not mined to any great
extent. There are a number of " pockets " of coal lying in isolated
areas east of the main field. Some of these are very thick but limited
in extent, Parker mentioning one where the coal is 80 feet thick
and consists of ordinary bituminous coal and cannel.

The seams of Missouri mostly lie nearly flat and the faults, while
numerous, are small. There are many horsebacks, concretions and
other obstructions in mining. Owing to the shallowness of the seams
in parts of the state, approximately 20 per cent of the annual output
is produced by the use of steam shovels. The coals are not high grade
as they are high in sulphur, moisture and ash. They are used as
domestic and steaming fuels.

1 Hinds, H., Missouri Bur. Mines and Geol., Vol. XI, 2nd series, 1912.

384 THE COAL FIELDS OF THE WORLD AMERICA

Kansas. 1 About 20,000 square
miles are underlain by Pennsyl-
vanian rocks in this state and it
is estimated that nearly three-
fourths of the area will prove pro-
ductive. The field lies in the
eastern portion of the state and
the most important and best-
known localities are in Cherokee
and Crawford counties which fur-
nish over 90 per cent of the coal.
The geological series are much
like those of Iowa only less dis-
tinctly marked, with limestone
more abundant in the lower series
and the coal distributed more
widely through the various forma-
tions. The thickness of the meas-
ures is about 3000 feet and on
the whole the beds lie nearly flat,
(Fig. 129). The Cherokee seam is
the main bed and it varies from 3
to 10 feet in thickness with an
average of about 40 inches. This
coal is washed and it may then
be coked but most of it is used for
locomotive and domestic fuel.
Much coal is mined by stripping
methods where it lies near the
surface. The weathered coal from
the pits is non-coking because of
oxidation. It is used raw in some
of the zinc furnaces.

In the Leavenworth district a

1 Howarth and Crane, Kansas Geol.
Survey, Vol. Ill, 1898. Also the Western
Interior Coal Field by H. F. Bain, U. S.
Geol. Survey, 22nd Annual Report, p. 339,
1902.

ARKANSAS

385

thin seam is mined at a depth of 700 to 1150 feet. This is the only
deep mining, according to Parker, which is carried on in the Western
Interior field. Another area occurs in the Osage County district where
a seam is mined at a horizon about 2000 feet above the Cherokee
bed.

A small lignite field also occurs in Kansas with coal of Cretaceous
age which is mined for local consumption.

Oklahoma. 1 The rocks carrying coal in . NMIESOF
Oklahoma apparently represent most of the COAL BEOS
Pennsylvanian formations. There are two main
fields, the Cherokee and the Choctaw, the latter
much the more important. The coals vary from
ordinary bituminous to semibituminous. Some
of the coals are coking and a number of ovens Paris
are operated, but most of the coke is too high in
sulphur for iron furnaces. There are about ten Charleston,
workable seams of which the following are the
best known: Hartshorne, Dawson, Henryetta,
McAlester, Cavanal and Witteville, upper and
lower. The Henryetta is the most important
seam in the Cherokee field and averages about
3 feet in thickness. The Hartshorne seams H"
run from 2 to 7 feet in thickness and the
McAlester coals about 4 feet. The strata are
much folded and faulted in parts of the fields,
and many of the mines carry considerable gas.

u PP er

Hartshorne

Fort Smith
375-425

Spadra
400-500

EG. 130 . Generalized
columnar section of the
coal-bearing rocks of Ar-
kansas. (After Collier,
U. S. Geol. Survey.)

Gulf Province

Arkansas. 2 The coal beds are well exposed
in this field and they have suffered consider-
able folding, faulting and erosion. They are
of Pennsylvanian age, Pottsville to Allegheny,
and the coals vary, even in the same seam,
from bituminous to semibituminous and semianthracite, the fuel
ratio increasing from about 5 on the western side of the field to

1 Taff, J. A., The Southwestern Coal Field. U. S. Geol. Survey, 22nd Annual Rept.,
Pt. Ill, p. 367, 1902.

2 Collier, A. J., The Arkansas Coal Field. U. S. Geol. Survey, Bull. 316, p. 137, 1906.

386 THE COAL FIELDS OF THE WORLD AMERICA

nearly 8 on the east. There are three seams, of which the Harts-
horne, corresponding to the seam of the same name in Oklahoma, is
the most important. This seam is about 8 feet thick and it
supplies nearly all the coal of the state. Other seams which are
mined a little are the Charleston, lying about 700 feet above the
Hartshorne and the Paris about 1000 feet above the latter seam.
There is some lignite lying in the lowlands southeast of Little Rock.
It is mined to a small extent but is practically undeveloped. It is
of Tertiary age and listed under the Gulf province.

Texas. 1 There are three fields in Texas with coals of three differ-
ent ages and grades. One of the fields in the north-central part of
the state belongs to the southwestern field of the Interior province.
The coal is Pennsylvanian in age and mostly of bituminous rank al-
though there are portions of it which might be more properly classed
as subbituminous. The Pennsylvanian is here divided into the fol-
lowing divisions in ascending order: Millsap, Strawn, Canon, Cisco
and Albany. The structure is simple, the basin dipping gently north-
westward and westward. There are three workable seams, two of
which are worked. They are thin, in few places more than 2 feet.
No. i seam is in the Millsap and the Cisco formation carries two
workable beds, one known as No. 7 which is the highest bed worked.
The coals are high in sulphur and ash and are therefore used mostly
for railroad and other steaming purposes.

The Eagle Pass field is a small one on the Rio Grande and it ex-
tends over into Mexico. The strata are considered to be of Upper
Cretaceous age and the coal is subbituminous in rank. The beds run
from 5 to 6 feet in thickness and dip steeply in parts of this field.

The large lignite field extends across the state from the Sabine
River to the Rio Grande. The rocks are of Eocene age and the coal
varies from woody lignite to subbituminous grade. The latter oc-
curs in the Laredo field along the Rio Grande where the rocks have
been compressed by the uplift of the Sierra Madre Oriental, a little
to the southwest, in Mexico. Campbell has pointed out that in the
southern part of the state the lignite consists chiefly of trees and
other coarse fragments of plants while in the northern part there is a
much greater proportion of spores, seeds and other related vegetal

1 Dumble, E. J., Texas Geol. Survey, 1892. Phillips, W. B., and Worrell, S. H.,
The fuels used in Texas. Bull. University of Texas No. 307, 1913. (Numerous analyses.)

NEW MEXICO 387

matter in the coal. The lignite occurs in the three upper divisions of
the Eocene at comparatively shallow depths and the beds vary from
a few inches to about 25 feet in thickness. Those being mined usually
run between 4 and 8 feet, except in Webb County where the coal
is subbituminous and the seams mined are less than 3 feet thick. The
lignite field belongs in the Gulf province. The known field is much less
than the probable field as the seams are largely unprospected. The
lignite is largely used for domestic purposes, for steam, and in gas
producers.

The Northern Great Plains and Rocky Mountain Provinces
These two provinces are considered together here since many
states are included in both of them.

Arizona. Arizona is not yet a producer and has not been well
prospected, but it contains several fields and a large reserve of coal
of subbituminous quality. It is of Cretaceous age. The main area
is the Black Mesa field, a flat, open, synclinal basin with coal in thin
benches. The other field of which something is known is the Deer
Creek field in the copper-bearing region of the state. This forms a
simple synclinal basin with the rocks greatly broken and the coal of
little value in the southwestern part. Two beds of workable thick-
ness running from 24 to 30 inches are reported by Campbell.

New Mexico. 1 This state contains coal varying in rank from
subbituminous to anthracite, the latter occurring where the coal has
been locally metamorphosed by igneous intrusions as in the Cerillos
field. There are five fields: (a) The Raton field of Coif ax County,
which is an extension of the Trinidad field of Colorado and will be
discussed under that state; (b) The San Juan River region, in-
cluding the Gallup and Monero producing districts, and extending
into Colorado; (c) A little-known area in Valencia, Bernalillo and
Sandoval counties; (d) The Los Cerillos field in Santa Fe County;
and (e) The Whiteoaks field in Lincoln County. Outside of the
Raton field the coal is practically all subbituminous and all the
coals of the state are regarded as of Upper Cretaceous age, chiefly
Montana, except in a very limited area near Pecos, carrying lower
Pennsylvanian coal. 2 Near Monero the coal is bituminous. Some

1 Storrs, L. S., The Rocky Mountain Coal Field. U. S. Geol. Survey, 22nd Annual
Rept. Pt. Ill, p. 449. Also U. S. Geol. Survey, Bulls. 285, 316, 381, 471 and 531.

2 Gardner, J. H., U. S. Geol. Survey, Bull. 381, p. 449, 1908.

3 88

THE COAL FIELDS OF THE WORLD AMERICA

of the fields, as for example the Carthage field, are complexly faulted
and igneous intrusions are common.

Colorado. 1 This state is the largest coal producer west of the
Mississippi. The fields of the state are as a rule divided into the
Eastern, the Park and the Western groups. The Eastern group con-
tains the following fields: Trinidad, Canon City and South Platte.
The Park contains the South, Middle and North Park. The Western
group is the largest and includes the Yampa field in the north, the
Danforth Hills, White River and Grand Hogback to the north of
Grand River, the Glenwood Springs basin, Crested Butte and Grand
Mesa just south of the Grand River, Book Cliffs near Grand Junc-
tion and the Durango field in the southwestern part of the state.

1000

2000

3000 Feet

FIG. 131. Section between Occidental and Oakdale mines, northwest of La Veta. Colo.
(After G. B. Richardson, U. S. Geol. Survey.)

The coals are subbituminous in the North Park field and Denver re-
gion, partly bituminous and partly subbituminous in the Durango
field, partly bituminous and partly anthracite in the Uinta Basin
region, and partly subbituminous, partly bituminous, and partly
anthracite in the Yampa field. The other fields all contain bitumi-
nous coals of varying grades. The anthracite and other high-carbon
coals occur in those areas where the coal has been highly compressed
or heated by igneous rocks and thus devolatilized. The same seam
may carry coal ranging from bituminous to anthracite, the latter
near the igneous rocks.

The age of the Colorado coals is mostly Upper Cretaceous, the
bulk of the coal occurring in the Mesaverde formation of the Mon-

1 U. S. Geol. Survey, 22nd Annual Rept., Pt. Ill, p. 427. Also Bulls. 297 (Yampa)
316 (Danforth Hills, Book Cliffs and Durango) 317 (Book Cliffs) 381 (Denver Basin,
South Park, Colorado Springs, Trinidad) Folio No. 9 (Crested Butte).

COLORADO

389

tana series. Some is Laramie, a little Dakota and a small amount
of Eocene age.

The Trinidad field forms part of the Raton Mountain area which
extends over into New Mexico. It is divided into the Trinidad
district to the south and Walsenburg district to the northeast. The
rocks are of Laramie age and the coal-bearing series varies in thick-
ness from 1500 to 3000 feet. In this field there are as many as eight

,_ - ,^' x ' v x '</;~\ v A "* r\. s ^ V s " / / \* *"" v -N X -" \ > ^ ^ ' s ./ i yS-N ^^/ x"^ / \ /^x ^ v ""-t ^ . N| _ f* .

-SCALE IN FEET

FIG. 132. Sills of igneous rock in "Laramie" formation and bed of natural coke,
in Purgatory Valley, near Trinidad, Colo. (After G. B. Richardson, U. S. Geol.
Survey.)

workable beds, varying from 2 to 14 feet in thickness in the lower coal-
bearing group of beds, which is about 250 feet thick. These beds
lie just above the Trinidad sandstone, and about 500 feet above the
sandstone is the middle coal-bearing group carrying at least four
seams, 2 to 4 feet thick. Lying about 1000 feet, on the average,
above the Trinidad sandstone, is the upper coal-bearing group of
shales carrying several seams, but these are unimportant so far as
known.

3QO THE COAL FIELDS OF THE WORLD AMERICA

The coal from the Trinidad field is bituminous, that from the
northern part being non-coking while that from the southern makes
an excellent coke. An interesting occurrence in the Walsenburg dis-
trict is the niggerhead coal described on page 235. The coal in some
of the seams adjacent to igneous rocks forms peculiar spherical struc-
tures known locally as " niggerheads " and consisting of quite high-
grade coal. Such bodies have been found in a few cases in other
fields where igneous rocks have intruded the coal seams. In some
places considerable natural coke, or carbonite, has been formed by
igneous rocks in the Trinidad field. The structure of this region
varies from places where the beds are practically flat and undis-
turbed to others where they are highly folded, faulted and intruded
with igneous rocks.

The Canon City field is a small one containing bituminous coal
in the Laramie formation. The rocks vary from flat-lying to
steeply dipping.

The South Platte field includes the counties around Denver and
contains subbituminous coal of Laramie age. The beds are com-
paratively flat except where the strata are more closely folded near
the mountains along the western border. The beds are fairly thick
in parts of the field and there are four of them in most places. The
coal is not of high grade and it is used chiefly for domestic and steam
purposes.

The North Park field is reported to carry very thick coals of bitu-
minous rank, some seams as high as 30 feet in thickness, but little
mining is done. No mining is now carried on in the South Park
field although some mines were operated during the last century.

The Yampa field occupies a large synclinal basin with several
minor anticlines and synclines running nearly parallel across it. The
strata are in a few places greatly disturbed by faults, but as a rule
the faults are of little importance. Most of the basin is not badly
folded. The coal-bearing series is the Mesaverde of the Montana
series of Upper Cretaceous. This series is about 3500 feet thick
and it is overlain by approximately 2000 feet of Lewis and Laramie
strata, the Laramie carrying thin beds of coal. The thickness of
the seams varies up to about 12 feet. In the Anthracite Range,
especially around Pilot Knob, there is some anthracite and natu-
ral coke produced by action of the igneous rocks which sometimes affect

UTAH 391

the coal for a distance of 50 feet or more. The coals in this field
vary from subbituminous to anthracite.

In the Danforth Hills and Grand Hogback fields, which represent
part of the Uinta basin region, there is one coal-bearing horizon,
the Mesaverde, and this is a distinct ledge-making formation be-
cause of the sandstone which it contains. The structure of this
region is simple as there are broad basins with minor folds, and
faults are not numerous. There are as many as seven seams varying
in thickness from 4 to 48 feet, making an aggregate thickness of
coal of about 108 feet. Some of these seams are separated by over
1000 feet of intervening strata. The mines through this region are
subject to much trouble with explosive gas and spontaneous com-
bustion of the coal.

In the Crested Butte district of the Uinta Basin region consider-
able anthracite has been formed by igneous activity and both bitu-
minous coal and anthracite occur in this field.

The Durango field, lying in the southern part of the state, extends
over into New Mexico in the San Juan River region and of the 73,900
square miles in this field only 1900 lie in Colorado. The coals in
this field vary from subbituminous to bituminous. Their geological
age is Upper Cretaceous, Dakota, Montana and Laramie. The
Mesaverde formation of the Montana carries the best coals, the
seams averaging around 5 or 6 feet in thickness. The Dakota coals
are not of much inportance, and while the seams in the Laramie are
very thick one reported to be as much as 80 feet the coal is
of an inferior quality to that from the Mesaverde formation. The
coal from several localities in the latter formation makes good coke.
The structure of the basin is comparatively simple except around
Gallup and in the southern end of the basin where the rocks have
been highly disturbed.

Utah. 1 The Uinta Basin region contains the largest area of coal
lands in the state and it extends across the Colorado boundary from
the Crested Butte district. The beds are deeply covered, going well
below 3000 feet in the centre of this basin, and probably out of reach
of mining operations. The coals are bituminous and coking. Prac-
tically all the coal mined in the state comes from the vicinity of

1 U. S. Geol. Survey, 22nd Annual Rept., Pt. Ill, p. 453. Also, Bulls. 316, 341, 415
and 47 1.

392

THE COM. FIELDS OF THE WORLD AMERICA

Sunnyside, Castlegate, Winterquarters and Clear
Creek. There are about 20 seams in this dis-
trict, with a maximum individual thickness of
about 20 feet. The seams occur in the base of
the Mesaverde (Montana) of the Upper Creta-
ceous. In the Coalville field, which is a small
one, two seams running about 7 to 14 feet in
thickness are mined. The coal is in the Colorado
series.

The other field is the Colob Plateau field which
carries a seam in the Colorado series from i to
10 feet thick. The coal varies from bituminous
to semianthracite and impure anthracite. Be-
cause of the closely folded nature of some of
the strata much of the coal is of poor quality.
In Kane County cannel occurs, and a little an-
thracite is found in Iron County.

Wyoming. 1 Wyoming probably contains the
second largest resources in coal of any state in
the Union, North Dakota coming first. The
coals of Wyoming are, however, of higher grade
than those in North Dakota since the coal in the
latter state is all lignite and that in the former
is not below subbituminous, while a considerable
amount of it is bituminous in rank.

The following regions are recognized: Black
Hills and Powder River regions of the Great
Plains province; the Bighorn Basin, Wind River
Basin, Green River Basin, Hams Fork region,
and the Hanna field, all of the Rocky Mountain
province. Of these areas the Powder River
region is the largest. It lies between the Bighorn
Mountains and Black Hills and runs from the
Platte River to the Montana boundary. It
represents the extension of the Fort Union
region of North Dakota. About 11,000 square

1 U. S. Geol. Survey, 22nd Annual Rept., Pt. Ill, p. 439.
Also, Bulls. 225, 260, 285, 316, 341, 381, 47i and 531, and
Prof. Paper 56.

NORTH AND SOUTH DAKOTA 393

miles are underlain with coal beds more than 3 feet thick. The rocks of
the field are of Fort Union (Eocene) age and they consist of a lower mem-
ber of 2500 to 2800 feet of dull-drab, bluish and brown shales and sand-
stone interbedded with many coal seams. The upper member is sub-
divided into the Tongue River, Intermediate and Ulm coal-bearing
groups. The sandy beds are in many places only slightly consoli-
dated. In the Tongue group which is about 800 feet thick there are
at least seven seams ranging from 5 to 32 feet in thickness. The
Ulm group is 900 to 1150 feet thick and there is a distinct horizon-
marker in the lower part of the group in the form of a shell bed which
in some places is directly overlain by a coal seam and in other places
separated from it by 30 to 40 feet of sand. There are two workable
beds in this group, the Arvade, 5 to 10 feet thick, and the Felix,
6 to 30 feet thick. The Ulm group contains the Lower Ulm or Healy
bed, 10 to 1 5 feet thick. The coal is all lignite and is used for domestic
purposes, steam, and producer gas. The structure of the basin is
very simple and the beds lie almost horizontal.

The main mining centers of the state are in Uinta and Sweet-
water counties. These areas furnish medium-grade bituminous coal.
Subbituminous coal is mined in Sweetwater, Carbon, Sheridan, Con-
verse, and Bighorn counties.

The coals of Wyoming vary in age from Lower Cretaceous, of the
Kootenay series in the Black Hills region, through the Mesaverde
formation in the Montana series of the Upper Cretaceous, to the
Fort Union of the Eocene. The older coals are of much higher grade,
as a rule. At Cambria a bituminous coal is mined from the Lower
Cretaceous rocks. In the Bighorn, Wind River, Hams Fork, and
Green River regions the coals are of Upper Cretaceous (Montana
and Laramie) and Eocene age. They vary from lignite through
subbituminous to bituminous and are non-coking. They are used
for domestic purposes, steaming and producer gas.

North and South Dakota. 1 North Dakota probably has the
largest reserve of coal of any state in the Union. The coal of the
Dakotas is, however, all lignite. It is estimated that nearly 35,000
square miles in North Dakota and 11,000 in South Dakota are un-
derlain with coal-bearing beds and that North Dakota contains 633,-

1 U. S. Geol. Survey, 22nd Annual Kept., Pt. Ill, p. 456. Also, Bulls. 285, 341, 381,
471, and 531.

394

THE COAL FIELDS OF THE WORLD AMERICA

329,800,000 tons of lignite. The coal is almost entirely in the Fort
Union beds of the Eocene. The beds run as high as 30 feet in thick-
ness and many of them are continuous for many miles. The Lance
formation contains a little coal, but in most places the seams are too
thin to work. The latter formation does not appear in the northern
part of North Dakota but is extensively distributed around the border

FIG. 134. Lignite seam, Williston, N. Dak. (After F. Wilder, photo. Reprinted by
permission from Ries' Economic Geology, published by John Wiley & Sons, Inc.)

between the Dakotas. The lignite is mined only along the main
lines of the railroad's and chiefly for domestic purposes, steaming
and producer gas.

Montana. 1 This state contains extensive coal lands. The Fort
Union Basin of the Dakotas extends into this state and contains
over half as much lignite as North Dakota in nearly the same
area. The other areas in Montana are the Bull Mountain field,
the Assinniboine region, the Judith Basin region, the Flathead River
field, the Mountain fields, the Yellowstone region and the Red Lodge-
Bridger field. The Bull Mountain field, which is being developed,
contains rocks of Fort Union and Laramie age or slightly older. The

1 U. S. Geol. Survey, 22nd Annual Rept., Pt. Ill, p. 460. Also, Bulls. 316, 341, 356
(Great Falls Field) 381, 531, 647 (Bull Mountain), University of Montana, Bull. 4, by Rowe.

CALIFORNIA 395

structure of the synclinal basin is simple. The coal varies from
lignite in the Tertiary rocks to subbituminous and low-grade bitu-
minous in the older formations. There are 20 seams over 2 feet
thick and the " Mammoth " seam runs from 8 to 15 feet.

The field which is most largely worked is the Red Lodge-Bridger
field where coal has been mined for a good many years. There are
seven seams running from 3 to 12 feet in thickness. The coal is
high-grade subbituminous, fairly high in moisture, and it soon breaks
down or " slacks " when exposed to the air.

The Great Falls field in Cascade County, forming part of the
Judith Basin region, produces considerable coal at Sand Coulee,
Stockett and Belt. The coal is bituminous and dirty and it occurs
in the Kootenay series of the Lower Cretaceous. The seams in some
places reach nearly 15 feet in thickness. The North Fork Flathead
River field is considered to contain unimportant bituminous and sub-
bituminous coals of Jurassic age as well as the Cretaceous coals. The
Assinniboine region is represented by the Milk River Field. The
strata belong chiefly to the Montana group and are buried under
glacial drift. All the coal in this field occurs in the Judith River
formation of the Montana series except a little lignite in the Fort
Union. The coal beds are, as a rule, lenticular and they run up to
9 feet in thickness. Faults and folds are common in this region.
The coal is of fairly good subbituminous grade. In many areas in
this state, as in the other western states, the coal beds have been
burned, leaving slag and reddened rock. This is partly due to the
ease with which the coal ignites.

The Pacific Coast Province 1

California. 2 The coal fields of California are very limited and
there is no prospect of her ever becoming a great coal-mining state.
The fields are also widely scattered, the main ones being as follows:
lone Mine in Amador County, Mount Diablo of Contra Costa Coun-
ty, Coral Hollow of Alamada County, Priest Valley and Trafton of
San Benito County, and Stone Canyon of Monterey County. The

1 Smith, G. O., The coal fields of the Pacific Coast. U. S. Geol. Survey, 22nd Annual
Kept., Pt. Ill, p. 473, 1902.

2 Campbell, M. R., Coal of Stone Canyon, Monterey County. U. S. Geol. Survey,
Bull. 316, p. 435, 1907-

396 THE COAL FIELDS OF THE WORLD AMERICA

coal in Stone Canyon is of bituminous rank with a composition
approaching cannel. A bed 10 to 14 feet thick has been exploited.

The coals in the southern part of the state are bituminous and non-
coking; those in the northern part are lignite, and those lying be-
tween these fields are subbituminous. Practically the only coal pro-
duced in the state, in some years at least, is lignite, which comes
chiefly from the lone Mine, Amador County. The coal is of Eocene
and Miocene age. The coal industry of all the western states where
fuel oil is found in abundance is vitally affected by that commodity
and will continue to be so affected as long as oil is abundant.

Oregon. 1 Oregon has very little coal and comparatively little
mining has been done. In the Coos Bay field, in the southern part of
the state, mining has been carried on and coal is shipped from the
Beaver Hill and Newport mines. The coal is subbituminous in
grade. The coal in this field is difficult to mine and much of it lies
below sea level. In the Eden Ridge field, also of Coos County,
the coal is bituminous and coking as the strata have suffered more
squeezing than in other parts of the county. The coal is shaly and
dirty. A number of other small fields in the state contain thin or
impure coal seams, but there is no development in these fields. The
Oregon coals are used for domestic and steaming purposes.

Washington. 2 There are five coal fields, confined to the western
and central parts of this state. They are the North Puget Sound in
Skagit and Whatcom counties, South Puget Sound in Pierce and King
counties, Puget Sound basin lying just east of Seattle, the Roslyn
field in Kittitas County on the east flank of the Cascade Mountains,
and the Southwestern field in Lewis and Cowlitz counties.

Washington is the only state in the Pacific province containing
coking coals. These coals are in the North and South Puget Sound
fields. The coals of this state range from subbituminous rank to
anthracite. Coal has been mined in Washington since about 1860,
the first mined being lignite, but spontaneous combustion closed oper-
ations. The bituminous coals are used chiefly on the ocean-going
ships and the subbituminous for domestic purposes.

1 Diller, J. S., Coos Bay Coal Field. U. S. Geol. Survey, igth Annual Rept., p. 309,
1899.

2 Washington Geol. Survey, Vol. II and Bull. 3. Also U. S. Geol. Survey, Bulls. 531
and 541.

ALASKA 397

The coals in King County lie under a heavy mantle of glacial
drift. They are of Eocene age, like the other coals of the state,
but owing to the compression which they have suffered in mountain
building they have been changed from lignite to subbituminous and
bituminous rank. In this county the beds have been highly folded
and broken so that in parts of the field mining is difficult. The
ash in the coal is high. Pierce County carries the best coals in Wash-
ington so far as known, as coals are bituminous, semibituminous
and even anthracite where the rocks have been highly squeezed,
broken and intruded by igneous rocks. The bituminous coals will
coke.

In the Roslyn field the beds lie regularly, and it is easy to mine
the Roslyn seam, running between 2 and 3 feet thick. There is
also another seam known as the " Big " seam which is full of part-
ings and very dirty. It reaches nearly 20 feet in thickness. The
coal is bituminous.

The Puget Sound field is characterized by the tremendous number
of coal seams which the formations contain. In one place there
are about 125 seams, the majority of which are unworkable. This
indicates a great number of changes, probably rapid ones, in the
climatic or topographic conditions, or both, during the formation
of these beds.

Alaska 1

The coal fields of Alaska are but partially known, as so little ge-
ological work has been done on this tremendous area. More or
less work has been done on certain regions and fields, and a rough
estimate of the character of the coals and their resources may be
given. The accompanying map and the following table show the
geographical and geological distribution of the coals, so far as known.

The following fields or areas are recognized: Bering River, Matan-
uska, Cook Inlet, Alaska Peninsula, Nenana, Northern Alaska and
many other less-known fields and areas.

1 Brooks, Alfred H., and Martin, George C., Coal resources of the world. Inter-
national Geological Congress, Vol. II, 1913. U. S. Geol. Survey, 22nd Annual Rept.,
Pt. Ill, p. 515, 1902; and Bulls. 284 and 314.

398 THE COAL FIELDS OF THE WORLD AMERICA

STRATIGRAPHIC POSITION OF ALASKAN COALS*

System

Series

Character of coal

Principal distribution

Quaternary

Pleistocene

Lignitic

Yukon basin and

other parts of Al-

aska.

Pliocene

Lignitic

Yakutat Bay and

other localities.

Tertiary

Miocene or Eocene

Anthracitic and bi-

tuminous. Chiefly

Bering River.

Eocene

lignitic, also some
bituminous and sub-

Throughout Alaska,
notably on Cook In-

bituminous

let, in Matanuska

Valley and Yukon

Basin.

Cretaceous

Upper Cretaceous

Subbituminous and

Alaska peninsula, Yu-

bituminous

kon and Colville

basins.

Jurassic

Lignitic, subbitumi-

Near Cape Lisburne

nous and bituminous

and in Matanuska

Valley.

Carboniferous

Pennsylvanian

Subbituminous

Yukon River.

Mississippian

Bituminous

Twenty miles south

of Cape Lisburne.

' Table by A. H. Brooks and G. C. Martin, Coal Resources of the World.

The Bering River is an important field lying 25 miles northeast
of Controller Bay. The coal beds run from 3 to 25 feet in thickness,
in the Kustaka formation which is about 2000 feet thick and of
Miocene age. The field is greatly folded and faulted and in many
places, especially in the eastern and western ends of the field, the
coal beds are so badly crushed as to ruin the coal. The coals vary
from anthracite, averaging about 81 per cent, to semibituminous
with 72 per cent fixed carbon. Some of the bituminous coal will
coke.

Another important field is the Matanuska, lying along the valley
of the Matanuska River, about 25 miles from Knik-Arm. The
measures are deeply covered with gravel in parts of the field. The
rocks are of Eocene age and in the eastern part of the field highly
folded and faulted. It is probable that the field will cover about 100
square miles. The seams range from 3 to 32 feet in thickness. In
the west end of the field the coal is lignite and in passing eastward
it changes to bituminous coal and anthracite. Some of the coal is
high in ash but the average content is favorable.

In the Cook Inlet field lignite occurs in the Kenai formation of

ALASKA

399

the Eocene. There are fifteen or more seams running from 3 to 7
feet in thickness. On the Alaska Peninsula lignite occurs in the
Kenai formation, but better coal is found in the Chignik formation of
the Upper Cretaceous around Chignik Bay and Herendeen Bay. In
this formation the coal is subbituminous and bituminous of fair
quality, but little is known of the extent of the seams.

LEGEND

COAL AREAS AND THEIR
POSSIBLE EXTENSION

SMALLER COAL AREAS "

AREAS KNOWN TO CONTAII
ANTHRACITE AND HIGH
GRADE BITUMINOUS COAL
AREAS THAT MAY CONTAIN
ANTHRACITE AND HIGH
GRADE BITUMINOUS COAL

[AREAS KNOWN TC
L [LIGNITE

FIG. 135. Alaska, showing distribution of coal deposits. (After A. H. Brooks.
Reproduced from "Coal Resources of the World." Published by the 1 2th Interna-
tional Geological Congress, Toronto, Canada.)

In Northern Alaska there are three coal-bearing formations: one
is Carboniferous, supposedly Mississippian, containing high-grade
bituminous coals with low ash content; another is Jurassic with a
large number of beds of subbituminous coal running as high as 1 2
feet in thickness; and the third is Tertiary, carrying lignite. The
older beds are considerably folded and faulted but those in the Ter-
tiary are quite flat.

In the Nenana field there are a number of beds running from 3
to 30 feet in thickness. They occur in the Eocene, and the coal
is mostly lignite.

400

THE COAL FIELDS OF THE WORLD AMERICA

The table given below is a summary of the estimates of Brooks
and Martin for the coal fields of Alaska, in so far as information is
available.

ESTIMATE OF TONNAGE OF COAL IN ALASKA*

Regions

Area in
square miles

Estimated amount of coal in metric tons
(i metric ton = 1.1023 short tons)

Total

Known
coal fields

<u %

Lignite

Sub-
bituminous

Bitumi-
nous

Semibitu-
minous

Anthracite
and
semianthra-
cite

Pacific Coast..
Interior Region
Arctic Slope...

458
440
312

8,585

4,493
3,059

1,971,000,000
9,731,000,000
910,000,000

485,000,000
53,000,000
3,143,000,000

2,000,000

14,000,000

1,293,000,000
60,000,000

1,931,000,000

5,682,000,000
9,798,000,000
4,113,000,000

Totals

1,210

16,137

12,612,000,000

3,681,000,000

16,000,000

1,353,000.000

1,931,000,000

19,593.000,000

* This estimate is based on seams 3 feet or more in thickness and lying less than 3000 feet deep for high-
grade coal (anthracite to semibituminous), and less than 2000 feet deep for lower grades (bituminous to lignite).

MEXICO

The coals of Mexico are but little developed. Only one state
produces any quantity and submits regular reports of production.
There are several regions, according to R. T. Hill 1 , which contain coal,
and the coals are of three geological ages: Tertiary, Upper Creta-
ceous and Triassic. The Tertiary lignites represent a continuation
of the deposits of that age in the United States, but so far as known
they are of no importance in Mexico. The Triassic coals occur in
two districts, the Mixteca district in the south where there are a
large number of seams of workable thickness but too high in ash
to be valuable, and the Santa Clara field where the coal is semi-
anthracite and anthracite because it has suffered much from com-
pression and igneous intrusions. Natural coke and graphite in suffi-
cient quantity to be mined have resulted from these disturbances.
The seams run 4, 8 and 10 feet in thickness.

The producing fields are all Montana (Upper Cretaceous), in age
and they occur in Coahuila. They are known as the Eagle Pass,
Sabinas and Barroteran fields. There is a small production from

1 Hill, Robert T., The coal fields of Mexico. Coal Resources of the World, Vol. II,
P- 553-

WEST INDIES 401

the Eagle Pass field, which is situated in the vicinity of Eagle Pass,
Texas and Porfirio Diaz in Mexico. This field is a continuation of
the field of the same name in Texas. In the Sabinas field there
are two beds 4 to 6 feet thick, of good, coking, bituminous coal.
A clay seam between the beds causes some difficulty in working.
The Barroteran field is a continuation of the Sabinas field along
the north side of the Santa Rosa Mountains. In this field the
seam is 8 feet thick with 14 inches of clay and shale and it is regular
and persistent. The coal is bituminous and coking. A number of
American companies are working mines in Mexico in the Sabinas
and Barroteran fields and a considerable number of coke ovens are
in operation.

CENTRAL AMERICA 1

The only countries in Central America reporting any coal re-
sources are Honduras and Panama. The former country reports
5,000,000 metric tons, all lignite except about 1,000,000 tons of
bituminous coal in the district of El Paraiso. The beds run from i
foot 6 inches to 4 feet in thickness, but they have never been mined.
Panama has a little lignite in the province of Bocas del Toro on the
coast and in the interior. That on the coast is largely submarine
and under porous strata while that in the interior is too high in sul-
phur to be valuable. It is interesting to note that the sulphur is
said to increase as the volcano Chiriqui is approached.

WEST INDIES

Cuba has no coal and the only resources reported for the West
Indies are found in Trinidad. The coal has not been exploited,
but there are two districts in which it is known to occur. These
are near Manzanilla and Sangre Grande on the east coast. In the
former area the coal is lignite, the seams thin, not exceeding 4 feet,
and the deposit is poor in quality. In the Cunapo district, near
Sangre Grande prospects are a little better. There are two seams
of subbituminous coal, one of which is 5 feet thick and can be traced
fcr a considerable distance, but they lie on an irregular bottom and
are probably not of much importance.

1 Coal Resources of the World.

402 THE COAL FIELDS OF THE WORLD AMERICA

South America

South America is apparently deficient in good coal deposits, and
very little definite information has been collected on her coal re-
sources as the best available data place her actual reserve at 2,089,-
000,000 metric tons and her probable reserve at 32,010,000,000 tons.
The geological ages of the coals are Permo-Carboniferous, Creta-
ceous and Tertiary, (Plate XV). The following countries are reported
to carry at least some coal: Colombia, Venezuela, Ecuador, Peru,
Bolivia, Argentina, Brazil and Chile. The coals vary from anthra-
cite to lignite in character.

Colombia. 1 Coal is found in several departments of the country,
but worked in few. Mines are operated in the vicinity of Bogota in
the Departments of Cundinamarca and in Boyaca and to a lesser ex-
tent in the Department of Antioquia. The coal is bituminous and
most of it is used locally for railroads, and for domestic and metal-
lurgical purposes. According to Gamba the largest fields are in
the districts of Cauca and Valle where there are three seams of medi-
um-grade bituminous coal, with an aggregate thickness of 6 feet
6 inches and estimated resources of 20,000,000,000 metric tons in
seams over i foot thick and less than 3000 feet deep. Little or no
mining has yet been done in these departments. The Departments
of Cundinamarca and Boyaca have the same number of seams with
the same aggregate thickness of coal and resources of 6,000,000,000
metric tons. The same number of seams with the same aggregate
thickness contain 1,000,000,000 metric tons in Antioquia. No es-
timate of the resources of the Department of Narino is available,
but they are believed to be very large as there is supposed to be a
large unstudied field in the vicinity of the Putumayo River. These
figures make a total estimate of twenty-seven billion tons in the
best-known fields. Miller and Singewald 2 quote Ospma as saying
that in the western coal area there are as many as six seams, one
as much as Q| feet thick. Most of the coal is a hard compact lignite
except where it has been subject to considerable metamorphism. Ap-
parently this coal is a subbituminous coal, as the term is used in the
United States.

1 Gamba, F. P., Coal resources of Colombia. Coal Resources of the World, 1913.

2 Miller, B. L., and Singewald, J. T. Jr., Mineral deposits of South America, p. 357,
1919.

CARIBBEAN

SEA

ritiba
Alegre
Pardo
lota.

Valparaiso f^ ;Mendoza

Santiao / Buenos Ai

Conce
Cuiriuina ni / San Rafael

SOUTH AMERICA

3CALE OF MILES

200 400

800 Statute Miles to 1 Inch

Capitals -.' Other Cities

Mesozoic Coals
Paleozoic Coals

Longitude

from 60

Greenwich

PLATE XV. Coal fields of South America. (Reproduced from "Coal Resources of
the World," published by the i2th International Geological Congress, Toronto,
Canada).

(403)

404 THE COAL FIELDS OF THE WORLD AMERICA

F. Lynwood Garrison 1 mentions some peculiar coal from Ca-
cagual on the Taraza River. There are several seams varying from
a few inches to 5 feet. The coal is compact and glassy and it re-
sembles cannel. It possesses a distinctly laminated structure and
it can be lighted with a match. It burns with a glow like punk and
not with a long flame as cannel does. This coal has the pe-
culiarity of being overlain by rich gold-bearing gravels. Analyses
show its composition to be as follows: Moisture, 13.6 to 15.36;
Volatile matter, 38.10 to 47.41; Fixed carbon, 44.40 to 32.67; Ash,
3.80 to 4.56 and Sulphur, 0.54 per cent. Garrison also quotes anal-
yses by Percy which show coals from Colombia with oxygen and
nitrogen combined varying from 12.06 to 22.12 per cent.

The better coals of Colombia are of Upper Cretaceous age. There
is considerable lignite of Tertiary age, but little is known regard-
ing it.

Venezuela. According to Miller and Singewald 2 coal is widely
distributed in Venezuela north of the Apure and Orinoco rivers and
the Llanos. The age is doubtful, probably Cretaceous and Tertiary.
All the coals are lignites or subbituminous except for one area of
semianthracite. There are numerous seams, the thickest reported
running up to about 10 feet. Some of the areas in the Balcelonia
district have been highly folded.

Ecuador, Peru, Bolivia. Ecuador does not report any operating
coal mines but this country has a little coal of good quality, varying
from lignite to anthracite. The places so far mentioned are at
Cojitambo, Mangan and Biblian in the province of Cafiar. Anthra-
cite occurs at San Antonio de Pomasqui, north of Quito. It is of
Tertiary age.

Peru has rather extensive coal-bearing areas running through the
Andes Mountains. The quality of the coal varies from low-grade
bituminous to anthracite. Her resources have been placed at ap-
proximately two billion tons, of which seven hundred million are
anthracite and semianthracite. The age of the coal is Cretaceous
or Tertiary. According to Borlkjof 3 , anthracite containing from 84
to 87 per cent fixed carbon, occurs in Cajabamba province, and in

1 Garrison, F. Lynwood, Mining and Scientific Press. Vol. 98, p. 219, 1909.

2 Op. cit., p. 542.

3 Borlkjof, J. Camilo B, The coal deposits of Peru. Eng. and Min. Jour., Vol. 88,
p. 983, 1919.

ARGENTINE REPUBLIC 405

Chota, about 140 miles from the Pacific, there are four anthracite
beds from 13 to 65 feet thick. There is estimated to be 700,000,000
tons of coal in this area. There is a large amount of coal in the Depart-
ment of Lima and in the Province of Chamcay, at Checras. In the
provinces of Parquin and Quiruragra there is a bed which reaches a
thickness of 13 feet and the resources are estimated at 720,000,000
tons. This is the largest and most important field in Peru. It is situ-
ated near the Cerro de Pasco copper camp and coal is being mined by
this company. A number of coal mines are worked in Peru, some
of them being highly gaseous. It seems probable that Peru will be
found to contain much larger reserves than those mentioned above
and that she will be quite an important producer of high-grade coal
in the future.

Practically nothing is known regarding the coal deposits in Bolivia
beyond the fact that they seem to be of small importance and to
be Permo-Carboniferous in age. A few outcrops of impure seams
occur on Lake Titicaca but little work has been done on them. The
inhabitants of that country, most of which lies at an elevation of
over 8000 feet above sea level, suffer a great deal from cold owing
to the great altitude and the scarcity of fuel.

Brazil. A number of coal mines have been operated from time
to time in Brazil, but so far very little coal sufficiently free from
slate and low enough in sulphur and ash to make a good industry
has been found. The extensive report of I. C. White 1 shows that
only by laborious picking, washing and briquetting can a satisfactory
fuel be obtained. The most favorable localities are in the south
near the Uruguay border. The coal occurs in the Rio Bonita beds
of the lower Permian which are correlated with the lower Karroo
of South Africa.

Argentine Republic. No coal deposits of importance have been
found in this great country. Thin seams are found in a number
of places, as the Permo-Carboniferous rocks outcrop along the eastern
border of the Andes and a seam has in recent years been exploited
at Salagasta in the province of Mendoza. It is reported that a
seam 10 to 12 feet thick was struck at a depth of about 2000 feet.
The coal is fairly low-grade bituminous. In Mendoza there are

1 Final Report of I. C. White,Chief of the Brazilian Coal Commission, Rio Janiero, 1908.

400 THE COAL FIELDS OF THE WORLD AMERICA

some beds of Albert! te which somewhat resembles coal but is a solid
derived from petroleum.

Chile. 1 There are two provinces in Chile which contain coal
fields of importance and in which coal is being worked. These
are Arauco and Concepcion. In the former the places where mines
are worked are Maquehua, Arauco, Pilpilco Cuyinco, and Lebu
and in the latter Penco, Lirquen, Coronel and Lota. The seams
worked vary in thickness from 0.70 meter to 1.85 meters. At Coro-
nel eight seams are mined and at Arauco six seams. In the Penco
district the coal is mined to a considerable extent beneath the sea.
The strata are little folded as a rule but normal faults are fairly
numerous. The age of most of the Chilian coal is Tertiary, probably
Oligocene or Miocene, and it is of bituminous rank; much of it being
of inferior quality. The coal resources of Chile are estimated at
2,082,000,000 metric tons.

1 Michado, Miguel R., Le Charbon du Chili et sa Distribution Geographique. Coal
Resources of the World, Vol. II, p. 581.

COAL AREAS OF EUROPE *

A A Ah ^S y t' v p Be /[ r J ^ ^\ ,

S^wl &{t*>, ( X

Sary.* ^tr^tJ "X-v

PLATE XVI. The Coal fields of western Europe. (Reproduced from "Coa

Toroni

:es of the World." Published by the i2th International Geological Congress,

CHAPTER XIV

THE COAL FIELDS OF THE WORLD EUROPE
AND ASIA

Europe 1

Europe was the mother of the coal-mining industry, which still
flourishes on that continent, although in some respects America
has surpassed her in the development of mining operations. Al-
though her resources are small compared with those of America,
Europe is well supplied with high-grade coal and she is more careful
to utilize a greater proportion of it than we have been in America.

The table given below shows the actual and estimated resources
of coal in the various countries of the continent and the accompany-
ing maps picture the area and distribution of the coal fields (Plates
XVI and XVII.)

This table indicates that the German Empire controls by far the
largest coal resources of the countries of Europe. Great Britain
comes second, Russia in Europe third, Austria fourth and France
fifth. Italy has almost no coal in comparison with her population.
Russia has a large estimated tonnage of anthracite almost twice
that of the United States and second only to China. The figures
given for Roumania do not properly indicate her probable reserves.
The annual production of European countries is given on page 335.

Great Britain. 2 Great Britain has long been one of the leading
coal-producing states of the world and she is surpassed in production

1 For comprehensive descriptions of the coal deposits of Europe see Atlas general des
Houilleres (Text and Atlas) by E. Gruner et G. Bousquet, Comite Central des Houil-
ISres de France, Paris, 1911. Also Coal Resources of the World, International Geological
Congress. Vol. I.

2 For comprehensive reports see the Coal Resources of Great Britain by A. Strahan,
Coal Resources of the World. Also various Memoirs of the Geological Survey of England
and Wales on individual fields. Analyses of British Coals and Coke and the Character-
istics of the Chief Coal Seams worked in the British Isles, by Greenwell and Elsden.
Colliery Guardian, London, 1907. Reports of the Royal Commission on Coal Supplies,
1905.

407

408 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA

*COAL RESOURCES OF EUROPE IN MILLIONS OF METRIC TONS
(i metric ton = 1.1023 short tons)

Actual Reserve

Probable Reserve

Total

Class of Coal

BandC

Anthra-
cite in-
cluding
some dry
coals

Bitumi-
nous coals

Subbitu-
minous
coals,
brown
coals and
lignites

Great Britain and Ireland:
England

8,672
2,500
172

B 79,869
B 31,402
B 18,876
B 8

B 46,030
B 195
B 1,685
B in

Wales

Scotland .

Ireland

Portugal

11,344
20

1,008
42

130.155

B 2,016
C 2,016
B 358
C 386

394

148
437

48,021

B 296
C 296
B 567
C 431

373

189,533

Spain:
Asturias

Other fields

France:
North of Ardennes Massif. .

Eastern
Armorican Massif

1,050
520

4,776

B 2,600
C 670
B 3

B 2

B 233
C 114

394
301

585
1,690

7
890

103

1,590

B 6,260
C 420
B 13
C 630
B 24
B 1,079
C 632

373
1,331

8,768

Central Massif

Alps

Lignite areas

Italy

581

3,622
159

301
51

2,690
143

270

9,058

C 30
3,923

B 7,oco
B 1,000
B 3-ooc

i,33i

48
30
358
50

17,583

243
40
388
50
4,402

Greece

Bulgaria

Denmark (Faroes)

Netherlands

Belgium

Campine:
Limburg

D'Anveres

Namur

11,000

EUROPE
COAL RESOURCES OF EUROPE (Continued)

409

Actual Reserve

Probable Reserve

Class of Coal

Total

BandC

Anthra-
cite in-
cluding
some dry
coals

Bitumi-
nous coals

Subbitu-
minous
coals,
brown
coals and
lignite

Germany:
Saar district

16,548
56,344
B 718
B 10,325
B 225
B 10,458
B 247

3,ooo

6,069
75
169

157,222

B 2,226
B 155,662

3,676
293
99

Westphalia

L Silesia

U Silesia

Saxony

Left of the Rhine

Other districts
North German States

Hesse

94,86s
B 4
B 2,970

B 2

B 106
B 57

9,313
354
12,231

1,700
58
3

37,599

315,110
B 109
B 38,012

B 43
B 8
B 2,525

B 18,014

B 253

4,068
1,250
663
1,976
426
36

1,578
43
25

423,356
i,7i7
53,876
3,676
529
39
H4

Bosnia and Herzegovina
Servia

Roumania

Russia;
Dombrova (Poland) .

Donetz . .

S. W. Russia

W. Urals

Caucasus

B 57

37,599

20,792
8,750

1,646

60,106
8,750

Total for Europe

13.046

236,716

24,427

41,300

456,446

12,255

784,190

* From the Coal Resources of the World. Estimate based on seams more than I foot thick and less
than 4000 feet deep and on seams more than 2 feet thick and between 4000 and 6000 feet in depth. For
detailed description of the classes of coal, see Classification of Coals, Chapter V.

410 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA

TABLE SHOWING THE GEOLOGICAL AGES OF EUROPEAN COALS

England and Wales

Scotland

Ireland

Portugal

Switzerland

.5
1

Denmark

Netherlands

Germany

Hungary

Austria

Bosnia-Herzegovina

Roumania

Sweden

Norway

"N
'5.

Russia m Europe

Pleistocene

Pliocene

Oligocene

Eocene . .

Tertiary undifferen-
tiated

Upper Cretaceous

)

Lower Cretaceous

Jurassic

Triassic (Rhaetic)

)

Permian

Upper Carboniferous
(Pennsylvanian) . . .

A
S
B

i
B

a
B

A
S

Sub-carboniferous
(Mississippian)

A
S
B

A
Be

Upper Devonian

A, Anthracite and semianthracite; S, Semibituminous; B, Bituminous; B, Subbituminous; L,
Lignite. Capital letters indicate important deposits and lower case relatively unimportant deposits of
the same type.

GREAT BRITAIN 41-1

only by the United States. She has given us many of our mining
methods and many of the principles involved in our mining apparatus
as well as a wonderfully efficient and hardy class of mining men.
Her coal supplies have been one of the very important factors in the
attainment of her high position in the industrial and commercial
world, and she has exported coal lavishly to those countries less
favored by nature in coal deposits than she. The tables given
above show that she is exhausting her supplies at a much greater
rate in proportion to her resources than any of the other great com-
mercial countries with the exception of France. The conclusion of
the Royal Commission on Coal Supplies in iSyi 1 was that there
was enough coal in sight to continue the existing rate of production
for 1273 years, but that, considering the probable rate of increase
in production, there was sufficient coal to last between 325 and 433
years. The latter figure would be much too high if the rate of in-
crease should continue a few years longer.

Several very thorough reports have been prepared on the coal
resources of the islands and the available supplies are very well
known. The fields are usually divided into two groups, known as
(a) the Visible and Proved fields; and (b) The Concealed and as
yet unworked fields. The first group includes those fields where
the Coal Measures are not deeply buried by later formations, and
the second group those fields where they are deeply covered but where
they are known to exist in synclinal basins. In computing the re-
sources it was assumed that a thickness of i foot of coal represents
960,000 tons per square mile, or 1500 statute tons per acre. The
various fields with the number and thicknesses of the seams, the
character of the coal and the resources of each field are set forth
in the following table compiled by Strahan.

1 Reports of the Royal Commission on Coal Supplies, 1871 and 1905.

412 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA

O O

g O

o o

I 58

cC | to

I M

P?<

CQPQPQ pq

,367

S-a

S 8
||l

111!

o S

s ?8S S a

O'MN

PQ PQ pq PQ pq PQPQ

pq < pq'pq pq w pq pq pq pq pq pq pq pq pq pq pqpq

pq <j <j pq pq pq pq pc ipq pq pq pq pq pq pq pq pq pqpq

1 4 4|

ia^ * BS

5555 .8.8.2 5 5 i 33

GREAT BRITAIN

413

In addition to the totals given above there are calculated to be
6,207,847,000 metric tons of actual reserve in seams running over 2
feet in thickness and lying at depths between 4000 and 6000 feet.

THE COAL RESOURCES OF SCOTLAND
(Including seams of i foot or over to a depth of 4000 feet.)

District

Coal Seams

Actual Reserve
(Calculations based on actual
thickness and extent)

No.

Thickness
(Aggregate)

Area,
sq.
miles

JClass of Coal

Metric tons
(Metric ton =
1.1023 short tons)

Clackmannan and Perth

17
38
40
6

37
25
Few
13
7
27
8
8

20 to 50 feet
100 to 140 ' '
75
I3l

105
59
Small
43
i6J
80
40
45
Unknown pos-
sible reserve
5

41
148
130
61

128 i
135
58
275
73
33

26J
2

B 2 ,B 3
B 2 ,B 3
B lt B 2 , B 3

BJ, BI

B. B 3
A lt A 2 , BI, B 2 , B 3
B 2
A lf A 2 , BI, B 2 , B 3
B 2
A., BI, B 2
B 2
Bi.Bi

916,243,044
5,263,432,444
4,252,000,000
683,663,883

3,143,148,115
1,600,629,550
324,187,635
3,051,734,030
134.965,370
1,337,992,870

1,000,000

Under the Firth of Forth

Edinburgh, Haddington and
Peebles

Stirlingshire
Dumbartonshire

Lanarkshire
Renfrewshire

Ayrshire

Dumfriesshire

Argyllshire (Marvern) . . . .

Sutherlandshire

21,376,493,625

1 For description of classes of coal see under Classification of Coals, Chapter V.

In addition to the actual tonnage reserve for Scotland mentioned
in the above table there are probable reserves of 1,685,000,000 metric
tons in seams over 2 feet thick lying between 4000 and 6000 feet in
depth in the Firth of Forth, and in the Fife and Kinross districts.

The coals of Great Britain are all of the higher ranks, bituminous,
semibituminous and anthracite. In England and Wales they all
occur in the Coal Measures proper, or the Pennsylvanian as the
term is used in the United States. In Scotland the Lower Carbon-
iferous (Mississippian) carries good coal and there are thin workable
seams in the Calciferous sandstone. The latter is a formation in
the lower part of the Lower Carboniferous and should not be con-
fused with part of the Devonian of America.

414 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA

In England and Wales the Millstone grit is well developed and in
some places it is very thick, reaching about 5500 feet in thickness
in Lancashire. As in America it consists of quartz conglomerate
and micaceous, arkosic sandstone. It carries small seams of coal.
In Scotland^it is in most places comparatively thin and it is a sand-
stone known as " Moor rock. " This rock also carries thin coal
seams.

The Coal Measures reach a maximum thickness of between 10,-
ooo and 12,000 feet in Wales and in the midst of the series there
is a sandstone and conglomerate known as the Pennant grit. It
is in many places almost barren of coal but in others there are a
number of good seams. In a few localities it carries pebbles of coal
showing that vegetal matter had already formed coal which could
be eroded when this formation was laid down. In many of the coal
fields, fire clay or " seat earth " is found beneath the coal seams,
leading early writers to consider that this was always an accom-
paniment of coal seams. Iron ore, in form of the carbonate, often
known as "black band, " occurs in a number of the fields. This
ore owes its origin to the presence of abundant carbon dioxide de-
rived from decaying vegetation in the waters when the iron was
laid down.

Cannel coal is abundant in some fields, and some of it carries
numerous fish remains showing that the spores which formed the
coal were laid down in ponds of open water where fish could live.
A peculiar coal known as Torbanite, which is a boghead, has long
been mined at Torbane Hill, Scotland. It is similar to an oil shale
in the products derived from distillation but it is nevertheless a
type of coal. Its status was once fixed by law in an important suit.

Some fields are greatly faulted as, for example, the Cumberland
field, and others are extensively intruded by basalt and other igneous
rocks, especially some of the Scottish fields and the Coalbrook-
dale and Dudley fields of England. Mining has been carried on
in England to a great depth, in some places exceeding 3000 feet.

South Wales. 1 -- This famous coal-field occurs in parts of Mon-
mouth, Glamorgan, Brecknock and Carmarthen counties. It oc-
cupies a syncline with steeply dipping strata on the southern limb.

1 Strahan, A., and Pollard, W., Coals of South Wales with special reference to the
origin and distribution of anthracite. Memoir Geol. Survey, England and Wales, 1915.

SOUTH WALES 415

The Coal Measures, which reach a thickness of nearly 12,000 feet,
may be divided into three divisions: a lower consisting mainly of
shales and containing the bulk of the coal seams; a middle series
known as the Pennant series consistly chiefly of sandstone and coal-
bearing only in the western part of the field; and an upper series
consisting mainly of shales carrying coal seams. The anthracite
occurs near the northwestern and western part of the field and the
same seams occur as bituminous coal in the southern and eastern
portions of the field with the well-known semibituminous, smoke-
less steam coals lying between the two extremes, (Fig. 33). In
one part of the field the anthracite reaches an undetermined depth.
There is one condition which remains almost constant throughout
the field and that is the higher fixed carbon of the coal in the deeper
seams. In any section there is in almost every case a nearly uni-
form increase in the fuel ratio with depth. This has not, however,
been responsible for the origin of the anthracite. Strahan and Pol-
lard concluded that they could find no satisfactory explanation for
the occurrence of the anthracite in one part of the field, semibitu-
minous in another part and bituminous in another, as there are no
igneous intrusions, there is no particular difference in the character
of the vegetation forming the coal in different parts of the field,
and the depth of burial or the length of time since burial will not
account for the changes. They also doubt that pressure could cause
the difference, but the writer believes that this is the only satisfactory
explanation. The relative proportions of the various varieties of
coal have been placed as bituminous 30.42 per cent; semibituminous,
or steam coal, 47.31 per cent; anthracite 22.27 P er cent.

In Glamorganshire the number of seams varies from twelve at the
eastern end with an aggregate of 42 feet of coal to about forty in
the western part with 120 feet of coal. In Pembrokeshire the Pennant
series is found throughout the field. The number of seams in the
eastern part runs from eight with 21 feet of coal to eighteen with an
aggregate of 33 feet in the western part. The strata are highly dis-
turbed and the coal is all anthracite.

It is believed that there is a large deposit of coal under Swansea
and Carmarthen bays. A large fault with a throw of approximately
3000 feet runs under Swansea Bay and cuts the coal field so as to
duplicate the measures.

41 6 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA

Ireland. 1 There are several coal fields in Ireland, the largest
being the Leinster field covering 95 square miles in Kilkenney, Carlow
and Queen counties. The coals occur in the Coal Measures and the
seams which are worked are quite thin, varying from i foot 8 inches,
to 4 feet. The Ballycastle field, 4! square miles in area, in County
Antrim, contains seams 4 to 6 feet thick in the Lower Carboniferous.
Numerous intrusions of dolerite cut this field. The Tyrone field
carries a number of seams in the Coal Measures running up to 9
feet in thickness and the Gortnaskea seam is 6 feet thick with 22
inches of cannel. Other fields are the Lough, Allen and the Tipper-
ary, besides other very small and scattered areas. In very few
places in Ireland have the Coal Measures been covered by later
rocks, and tremendous areas of these rocks have been eroded from
the island.

France. 2 France is deficient in coal for her future need as a
great manufacturing country, and during the Great War she was
cut off almost entirely from her best coal fields, which lie in the
northeast. The coal areas have been divided into five regions by
M. Defline as follows: (i) North of Ardennes Massif; (2) Eastern
area; (3) In Armorican Massif; (4) In Central Massif; (5) In Alps,
Maures, Pyrenees and Corsica.

The most important area is that of Valenciennes where the quality
of the coal varies from anthracite to high volatile bituminous. The
beds occur in the Westphalian series of the Coal Measures. There
are a large number of seams, in the north basin as many as 69, but
none are very thick, 2 meters being near the maximum. Parts of
the Coal Measures have been faulted beneath the Silurian and Dev-
onian formations and in the Pas-de-Calais basin the strata are ex-
tensively faulted and folded, (Fig. 73). A considerable amount
of coal lies more than 4000 feet from the surface. The Boulonnais
basin which is a continuation of that of Valenciennes is concealed
by Cretaceous and Jurassic strata and the coal has been reached by
borings. This basin is very small.

1 Cole, B. A. J., and Lyburn, E. St. John, The coal resources of Ireland. Coal Re-
sources of the World, Vol. II, p. 629.

2 Defline, M., Les ressources de la France en combustibles mineraux.' Coal Resources
of the World, Vol. II, p. 649. Reports on individual coal fields in the publications of the
Department of Public Works, Paris under the head of Etudes des Gttes Mineraux de la
France.

FRANCE 417

The basins in the east include Pont-a-Moussqn and Ronchamp.
The former is a prolongation of the Saarbruck basin and the Coal
Measures are completely concealed beneath Triassic and Permian
rocks at a depth between 2000 and 3000 feet. The measures belong
to the Stephanian and Wesphalian series and, judging from borings,
there are from one to seven seams with a maximum aggregate of
about 20 feet of coal, although the coal-bearing strata have not
been penetrated. Ronchamp field is in the small basin overlain
by Permian strata. The Coal Measures belong to the Stephanian.
There are 3 to 6 meters of bituminous coal in three seams.

FIG. 136. Coal mine near St. Etienne, France. (Photo by E. S. Moore.)

The basins in the Armorican Massif include the Cotentin, Maine,
Basse-Loire and Vendee. In the first field the coals are Stephan-
ian and are of little importance since they are thin and of poor
quality. The Maine field, in Brittany, contains coals of Dinantian
or Lower Carboniferous age. The coal is an impure anthracite and
occurs in very irregular seams, one reaching 60 meters in thickness
at one point. The Basse-Loire field is also of Dinantian age and the
rocks are highly folded and faulted. The coal is of poor quality.
The Vendee field is of Westphalian age and the coal beds overlie
gneiss and schist.

In the Central Massif there are a great number of small areas

41 8 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA

of which the St. Etienne basin, near the town of that name, is the
most important. The Coal Measures rest on granite and gneiss
and belong to the Stephanian series. The coal contains from
7 to 35 per cent volatile matter. There is one seam known
as the Grande Couche which reaches a thickness of 15 meters in
this field and 20 meters in the Commentry basin. The number
of seams runs as high as thirty-five in the St. Etiehne basin.

The other fields in this region are all small, and the rocks are of
Stephanian age. The Commentry basin is one of the most inter-
esting. It is 9 by 3 kilometers in diameter, and is characterized by
the large size of the boulders in the conglomerates in the Coal Meas-
ures. Some writers have suggested that these may be of glacial
origin and others that they may be due to torrential streams carry-
ing the material into a lake. It was in this basin that Fayol found
the trees with tops headed downwards, which he regarded as evi-
dence of drift origin. Some of the conglomerate in the Coal Meas-
ures carries pebbles of coal apparently derived from previously ex-
isting coal seams.

In the Alps seams of highly folded and for the most part inferior
anthracite outcrop at various points from Briancon to the Little
St. Bernard and run over into Italy and Switzerland. The seams
are irregular in extent and thickness and reach a maximum thick-
ness of about 10 meters.

Lignite occurs in an important basin known as the Fuveau basin,
also in less important areas in the Vosges Mountains and in the
Rhone basin. The Fuveau deposits are of Upper Cretaceous age
and the seams run up to 2 meters in thickness. The lignite in the
Vosges Mountains is Triassic and Jurassic in age and that in the
Rhone basin is Upper Cretaceous and Tertiary.

Spain and Portugal. 1 -- The most important coal-bearing provinces
of Spain are Asturias and Leon in the northwest and Teruel in the
east. In age the coals are Upper Carboniferous, Cretaceous and
Tertiary, and they vary from anthracite to lignite. In Asturias
there are as many as eighty seams with 112 feet of coal, but as a rule
the seams are not numerous and none of them are very thick. The
older coals are anthracite to bituminous and the Cretaceous and
Tertiary coals lignite or subbituminous.

1 Coal Resources of the World.

ITALY 419

Portugal has little coal. Near S. Pedro de Cova there is a folded
area of Coal Measures carrying anthracite, and near Tigueira the
upper Jurassic strata contain bituminous coal of medium quality.

Switzerland. 1 This is an old mining state in which coal has
been mined for over two and a half centuries. The reserves for the
future are not over 80,000 metric tons. The coal is Carboniferous,
Jurassic, Eocene and Pleistocene in age and on account of the ex-
cessive folding and compression which the rocks have suffered most
of it has been changed to anthracite and some of it even to graphite.

FIG. 137. Highly faulted and squeezed coal seam in the mountains of
Switzerland.

There is a little lignite of Eocene and Pleistocene age. The reserves
of Switzerland in metric tons are placed at 4000 tons actual and
50,000 tons probable reserve in anthracite, and 500 tons actual and
25,000 tons probable reserve in brown coal, or a total of 79, 500 metric
tons. Much of this coal is difficult to mine owing to disturbances
which the rocks have suffered.

Italy. 2 Italy has but little coal and all but about i per cent
of the coal produced is lignite or subbituminous in rank. Anthracite
of Carboniferous age occurs in many places in highly folded rocks
but most of it is of little economic importance. Most of the lignite
and subbituminous coal mined comes from Tuscany and Umbria
but these coals are widely distributed throughout the country. Beds
up to 30 meters in thickness are reported as occurring in Tuscany.
The age of the coal is Carboniferous, Triassic, Eocene, Miocene and
Pliocene.

1 Coal Resources of the World.

2 Coal Resources of the World.

420 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA

Belgium. 1 This country is comparatively well
supplied with high-grade coal. The seams all
occur in the Coal Measures which are divided
into the Upper or Stephanian and the Lower or
Namurian series, the former carrying the bulk
of the coal in the Flenu and Charleroi forma-
tions. There are three fields in Belgium: (a)
Dinant field in the southern part of the country
and including numerous isolated small basins
within a large syncline; (b) Namur field in the
central part of the Haine-Sambre-Meuse trough;
and (c) Campine field in the north. The Dinant
fieldas unimportant. The Campine field contains
the largest estimated reserves, they being placed
at 8,000,000,000 metric tons. This field has not
yet been worked as the coal lies deep and our
knowledge is confined chiefly to borings. The
Namur field is estimated to contain 3,000,000,000
metric tons reserve, and while there are numerous
seams they seldom exceed 2 meters in thickness.
The structure of the basin is complex, (Fig. 138).
In 1910 the average thickness of the seams worked
was 0.65 meters. The coal is chiefly bituminous
with some cannel. Part of this basin is very deep
and the deepest coal mines in the world, about
3900 feet, are found here. About one half of the
coals of Belgium are coking.

Netherlands. The Coal Measures in the
Netherlands, which only outcrop in the south
and east, are of the same age as those of Belgium
and those of Westphalia between which they form
a connecting link. The strata occur as great
fault blocks. There are five possible fields of

1 Renier, Armand, Les ressources houill&res de la Belgique.
Coal Resources of the World. Vol. Ill, p. 801. Also, Stanier,
X., Des rapports entre la composition des charbons et leurs con-
ditions de gisement. Annales Mines Belgique, V. 1900; and
Denoel, L., carte et tableau synoptique des sondages du bassin
houiller de la Campine. Annales Mines Belgique, IX, 1904.

GERMANY 421

which two are comparatively well known: (i) South Limburg with a
maximum aggregate of 38 meters of coal of anthracite and bituminous
rank; (2) South Peel of which little is definitely known but which
is likely to be a comparatively large field. The other fields are
known only by a few test borings. The coals are anthracite,
semibituminous and bituminous with a good deal of gas coal.

Denmark. Denmark has no coal production although before
1880 lignite was mined on Bornholm Island from Jura-Trias forma-
tions. There are nearly fifty seams but all are thin. On the Faroes
Islands and in Iceland coal of Tertiary age, which has been changed
locally from lignite to anthracite by basaltic flows and intrusions,
is mined for local use.

Germany. 1 Germany contains the largest supplies of coal of
any of the European countries so far as known. The coals are of
Carboniferous, Permian, Cretaceous, Tertiary and Pleistocene ages.
The Tertiary and Pleistocene coal is lignite, or Braunkohle, and
the Carboniferous is bituminous coal, or Steinkohle. There are six
districts containing Carboniferous strata, as follows: (i) Saar; (2)
Westphalia and Rhine province; (3) Lower Silesia; (4) Upper Silesia;
(5) Saxony; and (6) Left of the Rhine. Saxony contains some Permian
beds. There are considerable areas of Cretaceous coals which are
but little known and there are four districts containing lignite. The
latter are: (i) Prussia and the North German States; (2) Saxony with
Oligocene and Miocene beds; (3) Bavaria; and (4) Hesse, the latter
two containing coals in undifferentiated Tertiary formations.

The Saar district includes parts of Alsace-Lorraine, Prussia and
the Palatinate in which a large area of the Coal Measures (Ott-
weiler and Saarbruck formations) together with Permian and Meso-
zoic formations have been folded into a large anticline. Erosion has
removed the upper beds so that the Coal Measures are well exposed
except in the southwest portion where they are deeply buried and
much water in porous strata causes trouble in mining. The total
thickness of coal worked amounts to over 40 meters and the forma-
tions are divided in vertical section according to the types of coals
which they contain, as follows: The fat coal, the lower flaming coal
group, the upper flaming coal group, and the dry coal group. The

1 Die Kohlenvorrate des Deutschen Reiches. Coal Resources of the World. Vol.
Ill, p. 821.

422 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA

rocks have been extensively faulted and intruded by igneous rocks,
(Fig. 139). There are many deep mines in this district.

There is a connection between the coal-bearing formations along
the Rhine, in Westphalia, Holland, Belgium and France. The coals
occur in the Upper and Lower Carboniferous. In Westphalia and on
the right side of the Rhine the beds are gently folded and but little
faulted. On the left side of the river they are extensively faulted.

SECTION THROUGH THE SAAR COAL BASIN
(.AFTER HEISE-HERBST)

Neunkirchen Lebach

Lean CoalB Group Upper Lower Fat Coals Group

5 10 15Kio.

FIG. 139. Section through the Saar basin.

The Coal Measures are buried to a depth of 700 meters in some
places by Triassic, Cretaceous and Tertiary formations, and thick
deposits of quicksand in the latter formations have made special
mining methods necessary. On the left side of the Rhine the coal
may reach a maximum aggregate of 32 meters, while on the right
side the maximum thickness is about 30 meters with a maximum
of thirty-three seams.

The main feature in the Lower Silesian districts is the depth of
the basin, which exceeds 2000 meters in the center, and the Coal
Measures are deeply covered by Cretaceous and other rocks. The
basin is extensively faulted and crushed and igneous intrusions are
abundant, with the result that considerable coal has been coked
by natural processes. The mines are very gaseous. The coal is
chiefly Upper Carboniferous but to some extent Lower Carbonifer-
ous in age. The coal is described as being platy (probably splint
coal), fibrous and dull, and some of it is cannel coal.

Upper Silesia is a very important field, the second in Germany in
importance. It is noted for the number and thickness of its seams.
They are not so deeply buried as those of the Lower Silesian dis-

AUSTRIA 423

trict, not being over 150 meters below the surface, but the Carbon-
iferous strata are very thick. They reach 7000 meters in the south-
western part of the district. The coals are Upper Carboniferous
in age and the strata may be divided into a lower marine group
(Randgruppe) and an upper brackish group (Muldengruppe) . It
is near the base of the latter that the thick coal seams occur. In
the western part of the district there are said to be 477 seams con-
taining an aggregate of 272 meters of coal, 124 of these seams being
workable and carrying 172 meters of coal. In the eastern part are
105 seams of which 30 are workable, and they contain 62 meters of
coal. The Upper Silesian field extends into what were formerly
parts of Russia and Austria. It is highly folded but little faulted.

Coal mining has been carried on in Saxony since the tenth century
and the better seams are practically exhausted in the Lower Car-
boniferous strata. The coal is now procured on a small scale from
the Upper Carboniferous and Permian formations.

Lignite occurs extensively in Prussia and the North German States,
especially in the Saxony-Thuringia district. The beds range from
Eocene to Miocene in age. These lignites have been extensively
employed for briquetting and for the production of by-products, such
as gas, oils and paraffin.

Brown coals running from Miocene to Pleistocene in age occur in
parts of Bavaria, and a small deposit of Oligocene age in this prov-
ince is believed to be of undoubted drift origin.

Austria. 1 There are three main coal-bearing areas in Austria.
These are in the Alps, at the foot of the Alps, and in northern Austria.
In the Alps there are coals of Carboniferous, Triassic, Jurassic,
Upper Cretaceous and Miocene age. The Miocene coals are lig-
nites, the seams reaching a maximum of 12 meters in thickness.
The others are bituminous and occur for the most part in thin seams
although mined in many places. Along the foot of the Alps impor-
tant reserves of lignite occur in the Miocene rocks.

In parts of what was formerly northern Austria extensive depos-
its of lignite of Oligocene and Miocene age and also considerable
beds of Upper Carboniferous coal are found in the middle Bohemian

1 Petrascheck, W., Die Kohlenvorrate Osterreichs. Coal Resources of the World,
Vol. Ill, p. 1013.

424 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA

fields. Thick and numerous coal seams occur near the Prussian
boundary but they are covered deeply in most areas by later rocks.

Hungary. 1 Hungary, so far as known, is deficient in coal depos-
its. She has lignite, subbituminous and bituminous coal. The lig-
nite and subbituminous coals occur in the Jurassic, Cretaceous, Ter-
tiary and Quaternary formations and the bituminous coals in the
Carboniferous and Jurassic. The brown coals or lignites are the
only really important coals commercially. A considerable amount
of the lignite formerly belonging to Hungary is in Croatia and Slav-
onia.

Bosnia and Herzegovina. 2 The deposits of these states, like those
of many other countries in southern Europe, have not been fully
developed. Coals occur in Carboniferous, Permian, Triassic, Creta-
ceous and Tertiary formations, but the principal resources of these
provinces are in the lignites of Tertiary age in the Zenica-Sarajevo,
the Ugljevik-Priboj and the Baujaluka areas in the vicinity of Sa-
rajevo, in Bosnia. In the Tuzla basin northeast of Sarajevo there
are important Pliocene lignites with seams reaching 10 to 20 meters
in thickness.

Serbia. 3 Like the last-named states, Serbia has coal ranging
from Carboniferous to Tertiary in age. The upper part of the Coal
Measures lies on crystalline rocks and carries a few seams of mine-
able coal which in many places is impure and requires picking and
washing. The Upper Cretaceous carries good seams of coal and
also rests on crystalline rocks. The Jurassic coals are dirty but
otherwise of fair quality. The Cretaceous and Tertiary coals are
lignites. The mineral deposits of Serbia are as yet poorly devel-
oped.

Roumania. 4 The most important coal deposits of Roumania are
the Pliocene lignites and subbituminous coals of the Comanesti
basin. A little anthracite is mined in the Carboniferous of the Carpa-

1 De Papp, Charles, Les Ressources Houilleres de la Hongrie. Coal Resources of the
World, Vol. Ill, p. 961.

2 Katzer, F., Die Kohlenvorrate Bosniens und der Hercegovina. Coal Resources
of the World, Vol. Ill, p. 1075.

3 Milojkovitch, F. A., Die Kohlenvorkommen Serbiens. Coal Resources of the World,
Vol. Ill, p. 1093.

4 Marzec, L., and Tanaseseu, I., Les Reserves de Charbon de la Rumanie. Coal
Resources of the World, Vol. Ill, p. 1107.

TURKEY 425

thians. There is also some Mesozoic coal. The anthracite coal is
of little importance. Roumania has apparently not developed her
coals to any great extent and very little seems to be actually known
regarding her real reserves.

Montenegro. This state carries some good bituminous coal of
Carboniferous age, one seam on the Albanian frontier reaching over
6 feet in thickness. Little attempt has been made to develop min-
ing operations.

Greece. Coal is mined in Greece only at Coumi, but lignite
deposits of Tertiary age are widely distributed. The actual reserve
is placed at 10,000,000 metric tons and the probable reserve at three
times this figure. With the redistribution of lands in Europe, Greece
will receive from Turkey in Europe the principal coal field of that
country, lying near Keshan. This coal is of bituminous rank and
some of it resembles a hard cannel. There is also considerable Ter-
tiary lignite on the Marmora coast and at Telvino and Triano.

Bulgaria. 1 Bulgaria has extensive seams of coal although they
have not been developed and little attempt has been made to estimate
her reserves. The coals are of three varieties, anthracite, bituminous
coal and lignite. The anthracite lies in the Isker valley and while it
is comparatively dirty and the seams are thin the volatile constitu-
ents are less than 4 per cent. It is Carboniferous in age. Bitumi-
nous coal of Cretaceous age-is found in much-folded rocks in the Balkan
basin. This coal is used in making briquets and in coking. It is
very gassy. The seams are comparatively thin.

The Tertiary lignites and subbituminous coals are widely dis-
tributed and there are six main fields. In some places seams range
up to 12 feet in thickness.

Turkey. 2 Turkey has retained practically no coal lands in Eur-
ope. In Asia Minor there are a number of important fields of Car-
boniferous and Tertiary age. Along the Aegean and the Sea of
Marmora there are good Miocene and Pliocene lignites which are
mined locally. On the Asiatic coast of the Black Sea there
are bituminous coals in the Lower Carboniferous, or Culm,
and in the Westphalian and Stephanian series of the Coal Meas-
ures. The seams are numerous although not thick, and mining has

1 Bontchew, G., Coal Resources of the World, Vol. I.

2 Dominian, Leon, Coal Resources of the World, Vol. I.

426 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA

been carried on at a number of places. Some areas have been greatly
faulted. There is considerable coal, some of it anthracite, in the
eastern part of Asia Minor, in the provinces of Bitlis and Erzoom.
In the latter province lignite is mined. Lignite is also mined in
Syria, near Beirut. Coal has been mined to a small extent in Meso-
potamia.

Poland. The Dombrova basin contains many thick seams, es-
pecially those in the Reden group of rocks where one seam reaches
12 meters in thickness. The rocks are Carboniferous in age, (Penn-
sylvanian) and the system is thick. Much faulting has occurred.
The upper seams contain much ash and in many places the coal
is mined in open pits as the measures lie near the surface in parts
of the basin. The coal of Paleozoic age is bituminous, but the
northern part of the basin contains extensive lignite deposits which
are also mined. Other smaller basins which are not well known
occur in this country,. as well as in a small corner of the Upper Silesian
field which lies mostly in Germany.

Russia. 1 As indicated in the table showing the resources of Eur-
ope our information regarding the coal fields of Russia is rather in-
definite since very little knowledge has been gained concerning the
actual reserves. There are apparently very large resources in an-
thracite. The best-known basin is the Donetz which has furnished
most of the coal mined. This is the most important Russian area
and there are about 135 workable seams in the Lower and Upper
Carboniferous strata in this field. This basin is so folded and faulted
as to make mining conditions difficult in many areas. The fuel is
bituminous coal and anthracite, the latter forming about 13 per cent
of the output (Plate XVII.)

The Lower Carboniferous rocks form a great arc where they out-
crop and approach the surface in the Moscow district. The main
seams occur in the central part of the basin and they are known
chiefly from borings because they are deeply buried by Carboniferous
limestones. The coal is chiefly bituminous but some boghead, or
cannel coal occurs.

Considerable bituminous coal mining is carried on along the west
slope of the Ural Mountains in folded Lower Carboniferous rocks.

1 Tschernyschew, Th., and others, The coal fields of Russia. Coal Resources of the
World, Vol. Ill, p. 1149.

COAL AREAS OF RUSSIA

^Paleozoic ] jMesozoic Fi^ Tertiary
^ ^3

SO Longitude 35

East 40

50 100 200 300 400

L- i-

from 45 Greenwich 50

PLATE XVH. The coal fields of European Russia.

(427)

428 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA

Similar conditions exist in Siberia along the east slope where in ad-
dition to bituminous coal there is a great deal of lignite mined in the
Mesozoic and Tertiary formations and some anthracite is dug from
closely folded basins in Carboniferous rocks.

The Caucasus district contains coal of Jurassic and Miocene age,
the former bituminous coking coal and the latter lignite. The Tur-
kestan coals are of little importance so far as known but they are
in age Carboniferous, Rhaetic and Jurassic. The coals vary from
coking bituminous to anthracite.

Among the other districts, those of Sudjensk and Kuznetzk give
promise of being important as there is over 100 feet of coal in about
seventeen seams. The coal varies from high- volatile gas coal to semi-
anthracite and is Carboniferous in age. Numerous undeveloped
areas of Permian coal-bearing rocks are known to occur along the
Yenisei River but they have not been extensively prospected. The
coals are bituminous in character.

Considerable amounts of coal of Jurassic and Tertiary ages, vary-
ing from bituminous coking coal to lignite, occur in the Irkutsk
and other basins. The Russian Sakhalien carries coals of Upper
Cretaceous to Pleistocene age and of bituminous to lignite in char-
acter. Finland is without commercial coal deposits although small
quantities of anthracite have been found. Tertiary lignites are
widely distributed over European and Asiatic Russia.

Sweden, Norway and Spitzbergen. 1 Sweden has only a small
coal field, in the province of Skane, in the south. The fuel is high-
volatile bituminous to subbituminous coal and it occurs in Jura-
Trias formations (Rhaetic-Liassic) associated with fire clays. The
seams vary from 6 inches to 3 feet in thickness. The coal is mined
at a number of places and the estimated reserves amount to about
115,000,000 tons. Sweden's production of coal supplies less than
8 per cent of her requirements and the remainder of her supply is
imported.

Norway has no coal except a little on some of the northern islands.
On Ando Island a seam of high-ash cannel coal, i meter thick occurs
in Jurassic rocks. It has not been mined. Buren Island contains
coal of Devonian age not yet worked. This is probably the oldest
known coal in the world.

1 Coal Resources of the World.

^y> v i /

. I O / *^ *\ ^ '

Hfll .Ct V

COAL AREAS OF ASIA

Tertiary Coals
Mesozoic Coals
Paleozoic Coals

Longitude 80 East

PLATE XVm.

from 90 Greenwich

Coal fields of Asia.

titiL

ASIA 429

Spitzbergen has been known for many years to contain consider-
able deposits of good coal, and mining operations have been carried
on for a number of years by several small companies and by one large
American concern. The island is almost covered with snow and ice
most of the year, but sufficient information has been collected to
fix the age of the coal deposits as Carboniferous, Jurassic and Ter-
tiary. The only valuable Carboniferous coal so far located is at
the head of Ice Fiord, where a seam 7 meters in thickness occurs.
The Jurassic coals so far as known are unimportant. The Tertiary
coal occurs near the base of the Miocene and is a good quality of
subbituminous to bituminous coal. It is mined on Advent Bay
by an American company. All shipping must be done during about
three summer months owing to the unfavorable weather conditions.
The ground is said to be frozen to a maximum depth of about 400
meters but the Tertiary rocks in this area are thick and the mining
operations are carried on without great hardship in spite of about
four months of continual darkness. On account of the scarcity of
coal for domestic and industrial purposes in that part of the world
the Spitzbergen output finds a ready market.

Asia

Asia is well supplied with coal although little is yet known re-
garding very large areas of that continent. The following table
indicates the resources of the continent by countries and provinces
in the various kinds of coal, and the accompanying map of the con-
tinent shows the distribution of the coals, (Plate XVIII.)

This table brings out two important points. One is the enormous
resources of China in anthracite, although it seems probable that
considerable coal classed as anthracite may be nearer semianthracite
and semibituminous coal than true anthracite. In any case China
leads the world by a tremendous margin in -this commodity. The
other point is the lack of definite knowledge regarding the continent's
coal deposits. A few of the other countries, especially Siberia, un-
doubtedly have large reserves which are little known.

430 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA
'COAL RESOURCES OF ASIA (IN MILLIONS OF METRIC TONS)

Actual Reserve
(i metric ton = 1.1023 short tons)

Probable Reserve

Total

Class of Coal

BandC

Subbitu-

Anthracite
and semi-
anthracite

Bitumi-
nous coals

minous
coals and
lignites

Corea

B 4

C 9

China:

Chili

6785

B 6201

3.242

B 5,490

C 292

C 658

Shantung. .

1360

B 2842

640

B 2,241

Shansi

240

B 123

299,760

B 414,217

Shensi

1,050

Kansu

B 5,129

Honan

6,575

B 2,700

Kiangsu. . .

Anhui

B 187

Hupei

B 117

Chekiang. .

B 6

Chekiang. .

120*

Kiangsi

B 325

B 3,070

Fukien ....

80*

Kuangtung

498

256

B 255

Kuangsi . . .
Hunan. . . .

48,000

500
B 42,000

Szechuan. .

20,000

B 60,000

500

Kueichou . .

B 30,000

Yunnan. . .

B 30,000

100

8883

9783

378,58i

597,740

600

995,587

Japan:
Mesozoic

coals .

B 5

Tertiary. . .

C 5

Karaf uto .

C 17

C i,345

Hokkaido

C 336

C 2,106

233

Honsu

C i

C 14

478

Kyushu . .

C 542

C 2,374

Taiwan. . .

C 385

C 896

6,234

711

7970

Estimated by Kinosuke Inouye.

CHINA

RESOURCES OF ASIA (Continued)

431

Actual Reserve
(i metric ton = 1.1023 short tons)

Probable Reserve

Total

Class of Coal

Anthracite
and semi-
anthracite

B and C

Bitumi-
nous coals

Subbitu-
minous
coals and
lignites

B and C

Manchuria. .
Siberia. .

B 31
C 378

B 48

B 24.
C 30

C 119

222
3

20,002

B 223
C 508
B 66,034

B 53,037

C 210

B 22,657
B 246

C 28

107,844

2,327
50

1,208
173,879

20,002

Indo-China .
India:
Bengal,
Bikai and
Orissa

Central
India

Central
Provinces

Mesozoic
and
Tertiary . . .

Persia

221

225

76,178
B 1,858

2,377

79,001
1,858

Total in
Asia

8895

11,310

297

398,742

748,788

111,554

1,279,586

1 From Coal Resources of the World, Vol. I. Estimate based on all seams less than 4000 feet deep and
more than 14 inches thick, together with all seams between 4000 and 6000 feet deep and more than 2 feet
thick, of workable coal. For description of classes see Classification of Coals, Chapter V.

China. 1 The coal deposits of China are widespread. A very
large area occurs in northern China covering most of the southern
part of the province of Shansi, and another large field is found in the
south covering parts of Hunan, Kueichou, Yunnan and Szechuan
provinces. The age of the coals is Permo-Carboniferous, Rhaetic
(Triassic), Jurassic and Tertiary, and the coals vary from lignite to
anthracite. Some of the lignite is considered as Pliocene in age.
The anthracite and other low- volatile coals occur in areas which are

1 Drake, N. F., and Kinosuke Inouye, The coal resources of China. Coal Resources
of the World, Vol. I, pp. 129-214.

432 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA

more folded or compressed than the others, and considerable areas
have been so crushed as to be almost unmineable. It is stated that
in the Sieu River district in Hunan province, where much anthracite
is mined, the seams of anthracite average 15 feet in thickness, and
one seam, apparently of anthracite, is 50 feet thick. There is a
large amount of good coking coal in the country.

Korea. 1 Coal has been mined in Korea for many years but on a
small scale and in a primitive way. The coals are of Paleozoic (appar-
ently Carboniferous), Jurassic and Tertiary age. The Carbonifer-
ous coals so far discovered are of little importance but little is known
about the possibilities of the rocks of this age. The Jurassic coals are
most important. The Tertiary coals are lignites. Most of the coal
mined is semianthracite. It is powdery, and is sent to Japan where
it is made into briquets. Japan takes nearly all the production
and most of the coal used in Korea is imported.

Manchuria. 2 Manchuria has large resources in coal and there
are a large number of small mines operated in a primitive way. Large
operations are, however, being carried on in the important Fu-Shun
field. The age of the coal is Carboniferous, Jurassic and Tertiary.
The coals range from low grade bituminous to semianthracite. Most
of the coal mined is from the Tertiary and it varies from subbitu-
minous to bituminous. In this field one of the seams has a remark-
able thickness and mining has been carried on for many centuries.
It is stated that coal was mined here for a porcelain factory 600 or
700 years ago and that it was also used for copper smelting possibly
as far back as 3000 years ago. Mining was prohibited by the govern-
ment in the eighteenth century. The main seam in the Chien-
chin-chai section varies in thickness from 130 to 200 feet with nearly
a hundred thin partings aggregating about 20 feet. The quality
of the seam varies considerably where folded, shrinking to 75 feet;
and the partings increase to an aggregate of 70 feet in 130 feet of
coal. The coal is subbituminous to bituminous and is low in sulphur
and ash.

Japan. 3 Mining of coal has been carried on in a primitive way
in Japan for centuries, but about 1868 real, active mining began

1 Kinosuke Inouye, Op. cit., p. 215.

2 Kinosuke Inouye, Op. cit., p. 239.

3 Kinosuke Inouye, Op. cit., p. 279.

INDIA 433

under foreign engineers. The center of the coal-mining industry is
in northern KyQshu and large mining plants are also in operation in
Hokkaido. Chikuho, which is considered the richest and most im-
portant area, is well developed, and the Miike field is developing
rapidly. Japan exports a good deal of coal and imports little al-
though the imports from China are growing.

The coals of Japan are Triassic (Rhaetic), Jurassic, and Tertiary
in age. The Rhaetic and Tertiary are of most importance, the
latter being the best of all. Most of the Mesozoic fields are small
and scattered and they have suffered much from folding and igneous
intrusions. In the Tertiary the best coals occur in the Miocene.
There is some lignite in the Pliocene. Some semianthracite coal
occurs in the Mesozoic formations and natural coke occurs near ig-
neous intrusions. Most of the coal mined is bituminous, much of
it high-volatile. There is considerable coking coal.

The Ishikan coal fields are remarkable for the number of seams
and their thickness. In the lower series of the Tertiary there are
said to be as many as 150 seams, lens-shaped, and ranging from a
few inches to 60 feet in thickness. The coal is bituminous.

India. 1 Very little definite information is obtainable regarding
the extent of the coal deposits of India. They occur in the Gond-
wana system, of Permo-Carboniferous age, and in the Tertiary,
both in the Eocene and Miocene. There are unimportant and little-
known areas in the Jurassic and Cretaceous. The older coals
occur only in the Damuda series of the Lower Gondwana system.
The Damuda series overlies the Talchir series, which is of glacial
origin. The conditions in India strongly resemble those of South
Africa and Australia where the coal deposits of the Permo-Carbon-
iferous group are indirectly associated with glacial deposits and there
are the same types of plants in the Glossopteris flora.

The main Gondwana fields occur in the following provinces: Ben-
gal, Bihar and Orissa, Central India, Central Provinces and the
Nizam's Dominions, the most important being those of Bengal,
Bihar and Orissa. Active operations are carried on in the Ran-
iganj, Giridih and Jherria fields. The coal is of bituminous quality,

1 Hayden, H. H., The coal resources of India. Coal Resources of the World, Vol. I,
p. 353. See also Memoirs Geol. Survey of India, Vol. XLI, by R. R. Simpson.

434 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA

a good deal of it being of inferior grade. The seams have been in
many places intruded, broken and altered by igneous rocks.

In the Umaria field of Central India mining is regularly carried
on. In the Central Provinces there are three basins, Sarguja and
Chattisgarh on the northeast, the Satpura and Chindwara basin
on the northwest and the Godavari basin extending for nearly 300
miles down the Godavari and its tributaries. The possibility of the
rocks of the Sarguja basin connecting with the Satpura basin and
these again with those of the Godavari beneath the Deccan trap
has been suggested. This would give tremendous reserves not yet
exploited or computed. The Mesozoic and Tertiary coals occur in
Assam, and there is a group of collieries near Margherita opera-
ting on seams aggregating 80 feet of coal. The coal is friable and
high in sulphur. In Baluchistan a colliery is operated at Khost, but
the seams of this district are thin and limited. Burma so far as
known has little good coal.

With regard to the countries adjacent to India, it is reported that
Afghanistan apparently has large coal deposits, but little is known
regarding them. Thibet has no coal so far as known.

Persia. 1 Coal is widely distributed over Persia and is mined
by primitive methods for local use, in a great number of places. Very
little is known regarding the extent or quality of most of the seams.

BRITISH NORTH BORNEO 2

The coal in this island is lignite and low-grade bituminous coal, and
it is almost all of Tertiary age. The better coal is Eocene but there is
some in the Oligocene, Miocene and Pleistocene formations. A num-
ber of mines are worked and the labor is chiefly Chinese, Malay
and Javanese. At Brooketon in the State of Sarawak, there are
five seams with thicknesses of 28, 26, 29, 5 and 2 feet respectively.
The first two of these seams are worked. The beds are tilted up
to 80 degrees. The coal is very low in ash, one analysis showing only
1.58 per cent, and sulphur is low. Spontaneous combustion occurs

1 Rabino, H. L., The coal resources of Persia. Coal Resources of the World, Vol.

I, P- 365-

2 Evans, J. W., The coal resources of British Territory in North Borneo. Coal Re-
sources of the World, Vol. I, p. 89. Also see Coal Mining in Borneo by James Roden.
Trans. Inst. Min. Eng., Vol. 28, p. 240, 1904-05.

THE PHILIPPINE ISLANDS 435

under favorable conditions and there is a large amount of water in
the mines. This field apparently extends under the sea to the north
end of the Island of Labaun. Some of the coal contains a large
amount of resin which the natives use for lighting purposes. The
Silimpopon coal field on the river by that name is near the coast
and shipments can readily be made. There is little gas in the mines
and open lights are used.

DUTCH EAST INDIES, OR NETHERLANDS INDIA 1

A large amount of coal is distributed through these islands. It
is all Tertiary in age, Eocene and Pliocene. The coal is of lignitic
and subbituminous rank. The production of the island of Sumatra
amounts to about half a million tons a year and this comes chiefly
from the Soegar area of the Ombilin field in which some seams reach
a thickness of over 30 feet. The other field on the Sepoetih River
is not of much importance. Java contains some coal but the seams
are thin. Borneo has a much larger supply with more and thicker
seams than the other islands. The probable resources of all the
islands are probably about one billion tons.

THE PHILIPPINE ISLANDS 2

The important deposits of the Philippines are all Tertiary, chiefly
Miocene in age, and these coals are mostly lignitic and subbituminous,
with a little coal of bituminous rank. The total known area under-
lain with coal seams amounts to about 53 square miles of which
less than 7 square miles are of workable quality. There is a much
larger unprospected area which will no doubt prove to contain val-
uable seams. The fields occur on the islands of Baton, Cebu, Min-
danao, Masbate, Mindoro and Luzon. On Luzon Island the coal
is around Sugud Bay, and on the Island of Mindanao it is on Si-
buguey Bay in the southwest corner of the island. Of these fields
those on Baton and Cebu islands are regarded as most important.
On the former island there are estimated to be about 26,000,000
tons of subbituminous coal in two to eight seams, 3 to 12 feet thick.
The western part of the field is highly faulted and folded.

On the island of Cebu the coals lie from 8 to 15 miles from the sea.

1 Douglas, E. A., Coal Resources of the World, Vol. I, p. 95.
* Dalburg, F. A., Coal Resources of the World. Vol. I, p. 107.

436 THE COAL FIELDS OF THE WORLD EUROPE AND ASIA

The coal is subbituminous and it occurs in a series of faulted and
folded Oligocene and Miocene strata over 2000 feet thick. Some
of the seams reach a thickness of 15 feet. The coal on Mindanao
and Polillo islands is classed as bituminous by Dalburg. That on
Mindoro Island near Bulalacao is lignite and the seams, six in num-
ber, run up to 12 feet in thickness. On Sugud Bay, Island of Luzon,
the seams of subbituminous coal vary from 10 to 27 feet in thickness.
The beds are considerably folded in parts of the field.

The Philippine coals are used chiefly by inhabitants of the islands
for domestic purposes and on ships, and in recent years several mines
have been operated on a fairly large scale. In most cases these
are controlled by American mining men. Scarcely any of the coal
cokes well. The total resources of the islands are placed at: bitu-
minous coal, 4,959,200; subbituminous coal, 31,285,200; and lig-
nite (black) 30,092,000 metric tons. Apparently the black lignite
mentioned in the reports would be largely classed as subbituminous
coal in this country according to our present custom.

Longitude 20" West

PLATE XIX. The coal fields of Africa. (From "Coal Resources of the World,"
published by the i2th International Geological Congress, Toronto, Canada.)

(437)

CHAPTER XV

THE COAL FIELDS OF THE WORLD AFRICA AND

OCEANIA

Africa 1

The Dark Continent is so large and there is so much of it which
has not been thoroughly explored that anything like an attempt to
accurately describe its coal deposits is impossible at this time. The
accompanying map (Plate XIX) shows the distribution of the coals
so far as known and the following table gives the estimates of the re-
sources as compiled by the International Geological Congress in the
year 1913.

RESOURCES OF AFRICA

Actual Reserve
(In millions of metric tons)
''i metric ton = 1.1023 short tons)

Probable Reserve
(In millions of metric tons)

Class of Coal

Total

Class A

Anthracite
and some
dry coals.

Classes
B and C

Bituminous
coals

Class D
Subbitumi-
nous coals.
Brown coals
and lignites

BandC

Belgian Congo
Southern Nigeria . . .
Rhodesia

B 306
C 37

80
74

4700
6000

960

B 90

B 119

C 31

B 28,800
C 7,200
B 4,600

B 2,880
C 960

900

990

569
56,200

South Africa:
Transvaal

Natal

Zululand
Orange Free State..
Cape, Basuto and
Swaziland

1, 660

44,440

Total

343

154

1, 660

44,680

57,839

For detailed description of classes see Classification of Coals, Chapter V. The reserves are
figured on all seams which are i foot or over in thickness and less than 4000 feet deep; and on all
seams of 2 feet and over which lie between 4000 and 6000 feet jn depth.

1 For detailed descriptions of deposits in Africa see Coal Resources of the World,
Vol. II, pp. 375-428. Also Colonial Reports of the Museum of the Imperial Institute,
London; Reports of the Department of Mines, Union of South Africa.

438

SOUTHERN NIGERIA

439

The geological ages of the coals of Africa are indicated in the table
given below:

GEOLOGICAL AGES OF AFRICAN COAL DEPOSITS

r -3

'ca

Abyssin

a 1

^Z
eg

Rhodesi

o 8,

l a

Pleistocene

Tertiary

1 b

Upper Cretaceous

Triassic including Rhaetic .

R s

Permian

Permo-Carboniferous

A, Anthracite; S, Semibituminous; B, Bituminous; B, Subbituminous; L, Lignite; C, Cannel.
Capital letter indicates important deposits, lower case unimportant or unworkable deposits.

The main coal fields of Africa are in the southern portions of the
continent. Egypt has traces of lignite and bituminous coal but
nothing workable. The Anglo-Egyptian Sudan is also lacking in
workable coal although traces of lignite have been found. Abys-
sinia is little better off, but according to Dum and Grabham the
natives mine coal near Addis Abbaba, the capital of Abyssinia. The
East Africa Protectorate has no workable seams and Madagascar
has a very limited amount so far as is at present known. In the
lanapera area of the island there are several seams reaching a maxi-
mum thickness of 8 feet 4 inches, and according to Bonnefond the
coal is like cannel in character.

Southern Nigeria. In southern Nigeria good subbituminous coal
and lignite have been discovered. The former is probably of Creta-
ceous and the latter of Tertiary age. According to J. W. Evans,
the best-known lignite areas occur in the vicinity of Onitsha and
Asaba on the other side of the Niger River. In the latter locality
six seams of lignite ranging from 8 to 20 feet in thickness have been
examined, and this coal was found to make good briquets when
tested in Europe and compared with the German lignites. The

440 THE COAL FIELDS OF THE WORLD AFRICA AND OCEANIA

seams of subbituminous coal reach nearly 6 feet in thickness and
they outcrop in the escarpment about 45 miles east of the Niger
River.

Nyassaland has very little coal which is sufficiently clean to be
utilized.

Rhodesia. The Wankie coal field is the only one in Rhodesia
where coal is being mined. This field lies about 60 miles south-
east of Victoria Falls on the railroad line to Bulawayo. The coal
lies in the basin of the Zambesi River and like the other fields of
South Africa it occurs in the Karroo series which apparently in-
cludes rocks ranging in age from Carboniferous to lower Jurassic,
with no well-marked lines of division between them. The main
coal-bearing formation is in the Lower Matobola which corresponds
to the Ecca series of Cape Colony and the High Veld coal measures
of the Transvaal. It lies just above the Dwyka conglomerate which
is of glacial origin and usually regarded as of Permian age. Some
geologists have considered at least some of the coal beds as of the
same age as the Rhaetic of Europe. The seams are comparatively
shallow in depth and vary from i foot to 12 feet in thickness.

The other fields of Rhodesia are the Mafungabusi lying just north-
east of the Wankie field, the Lufua and Losita about 50 miles to the
northwest of the latter field, and the Luano some 75 miles east of
Broken Hill, on the railroad line. A small field near Tuli lies about
150 miles southeast of Bulawayo, and another on the Sabi River,
near Sabi, 225 miles southeast-by-east from Bulawayo. These two
fields are not on a railroad. It is supposed that a concealed field
lies beneath the Victoria Falls basalts. The largest number of seams
explored is in the Luano field where four have been found reaching
an aggregate thickness of almost 18 feet. The thickest single seam
is in the Wankie field and it runs up to 12 feet. The ash in the
Rhodesian coals is high like that in the coals of South Africa, most
of them running over 13 per cent.

Belgian Congo. In the Belgian Congo there are two coal fields
according to Renier, known as the Lukugo and Lualabo. The coals
in the former field are regarded as of Permo-Carboniferous age and
there are three flat-lying seams running over 10 feet in thickness.
The coal is much lower in ash than much of that in South Africa.
It averages around 10 per cent. In the Lualabo field the coal is

UNION OF SOUTH AFRICA 441

probably of Triassic age and there are several seams several feet in
thickness. It is of inferior quality, however, as much of it is high in
sulphur and very high in ash.

Union of South Africa. The coal deposits of the Union of South
Africa occur in the Karroo series which apparently includes rocks of
Carboniferous, Permian and Triassic ages as they are known else-
where. The seams usually lie within 200 feet above the Dwyka
formation, the basal conglomerate of the Karroo series. Much of
the coal is undoubtedly of Permian age and the same peculiar plant
associations, usually known as the Glossopteris or Gangamopteris
flora, which are found in the coal measures of India and Australia,
are found here associated with the glacial deposits. The coal is
practically all of the bituminous variety. A little lignite occurs in
Cretaceous and Tertiary rocks but it is unimportant. One feature
of most of the coal is the high ash content which runs from 6 to 30
per cent and averages between 10 and 15 per cent.

Transvaal: In the Transvaal the coal seams lie quite flat and
occupy the high lands. They are usually of shallow depth, those
worked being less than 400 feet deep. Many of the deposits occupy
rather limited and isolated basins owing to the topographic con-
ditions existing when they originated. They are also associated
with coarse sediments, and some writers have considered that practi-
cally all of the South African coals are of drift origin, but in certain
places stumps and roots are found in place beneath the seams indi-
cating their in situ origin. In the Transvaal the main field is the
Witbank or Middleburg and in it there are five known seams, giving
an aggregate thickness of about 56 feet of coal. The average thick-
ness of the seams worked runs around 10 feet, the maximum reaching
about 20 feet.

Cape of Good Hope and Natal: In these provinces as in the
Transvaal, the coal occurs in the Karroo series, but near the top.
The Dwyka lies at the base of the Karroo in this region as elsewhere
in South Africa and includes a thick glacial till. The coal occurs in
the Molteno beds which are younger than the beds containing the
coal in the Transvaal and they are apparently of Rhaetic (Triassic)
age. The mines are worked by adits and the workings are confined
largely to the portions of the seams near the outcrops, because many
of the seams have been so broken up by intrusions of igneous rock

44 2 THE COAL FIELDS OF THE WORLD AFRICA AND OCEANIA

that their extent is uncertain. Much of the coal has been devolati-
lized and anthracitized by the heat of these intrusions. A consider-
able amount of the coal is semianthracite and it is high in ash, usually
above 20 per cent. It is low in sulphur but a large amount of clinker
is produced and it is said that this clinker is taken care of on the
locomotives by specially designed fireboxes. There are some beds
of lignite of Tertiary age but they are not of much importance.

In Natal, the coal, which is similar to that in the Cape of Good
Hope Province, has been extensively intruded by igneous rocks and
to quite an extent converted into semianthracite. Many of the
mines are sufficiently gaseous to require the use of safety lamps.

The coal industry in Africa is very young and much will be added
in the coming years to our knowledge of the geology and the coal
resources of the continent. From the general character of the ge-
ological conditions on the continent, however, it seems improbable
that Africa will ever be, comparatively speaking, a great coal-produc-
ing continent.

Oceania 1

Oceania includes, for the purposes of this discussion, the continent
of Australia and the islands of New Zealand and Tasmania.

Australia's reserves of high-grade coal are considerable, although
they are smaller than those of Great Britain and very small compared
with those of the United States or Canada, two countries to which
Australia is almost equal in size. The table given below shows the
estimated reserves for New Zealand and the various states of Aus-
tralia. The latter country holds the record for the thickest coal
seams in the world. There are two seams of brown coal in Victoria,
which are 266 and 227 feet, respectively, in thickness.

1 For comprehensive reports see The Coal Resources of the World, Vol. I. Also
Coal-fields and Collieries of Australia by F. Danvers Power (Critchley Parker). Hand-
book for Australia, British Assn. Adv. Sci. 1914. Reports of the various state Geolog-
ical Surveys and Departments of Mines.

ioa

COAL AREAS OF OCEANIA

SCALE OF MILES

100500 200 400 600 800

Tertiary Coals

170

ON
ISLANDS

&NE.W

FIJI ISLANDS Cx?

VETI

NEW
CALEDONIA 1

NORT
Auck

North Cape

ISLAN

Bast
Cape

sou
N

ISLAND

NEW

Blen-y?"' 61 " 11 ** 011
Hrhein7%

ZEALAND

tchurch

Dunedin

U0 from Greenwich 150

OCEANIA

443

iCOAL RESOURCES OF OCEANIA
(In millions of metric tons, i metric ton = 1.1023 short tons.)

Actual Reserve

Probable Reserve

Class of Coal

Total

B and C

BandC

Anthracite
and some

Bituminous

Brown
coals and

dry coals

lignites

Australia:

New South

Wales

B 118.4.30

Victoria

B 40

B 12

3IH4

Queensland. . .

B 1766

<;6o

B ii,on

800

C 165

C 7Si

West Australia

153

500

Tasmania

B 65

C i

1971

219

560

130,279

32,H4

165,242

New Zealand . . .

B 26

612

B 99

1,863

C 363

C 423

3,386

2360

831

560

130,801

33.977

168,628

1 These figures are based on seams I foot and over to a depth of 4000 feet; and 2 feet and over between
4000 and 6000 feet in depth. Coal Resources of the World, Vol. I. For description of classes of coal, see
Classification of Coals, Chapter V.

Geological age of coals: The geological ages of the coals in Oceania
vary from Carboniferous to Tertiary, the most important fields being
Permo-Carboniferous (Permian). The latter are closely related to
the coal deposits of India and South Africa and to some of those of
South America. These deposits are characterized by the same pe-
culiar plant associations, as Gangamopteris, Glossopteris and Rhacop-
teris are among the outstanding fossil plants of the Australian coal
measures. Lepidodendron, so abundant in the Coal Measures
throughout the rest of the world is present in the Devonian and
Carboniferous rocks in Australia but absent in the Permo-Carbon-
iferous, as the violent changes in climate wiped out this and related
genera and ushered in the Glossopteris flora. The same interesting
glacial conditions prevailed in Australia in the Permo-Carboniferous

ffU

W>T jBSiig

oiog- UJ9JTS8M. _

444 THE COAL FIELDS OF THE WORLD AFRICA AND OCEANIA

as in India and South Africa and the
same difficulty is experienced in trying
to separate the Carboniferous from the
Permian.

The other geological systems carrying
important coal seams are the Triassic
in Tasmania, the Jura-Trias in Queens-
land, the Upper Cretaceous in Queens-
land and New Zealand, the Miocene
in Victoria and the Tertiary in New
Zealand. The rank of the coal varies
from bituminous and anthracite in the
Permo- Carboniferous to bituminous and
lignite in the Mesozoic and lignite in the
Tertiary formations.

New South Wales. 1 The coals of
this state are of high grade and are
bituminous in rank. They are valuable
as gas, domestic and steaming coals.
Much of the coal is of good coking
quality. There are four important
fields, the Maitland, Newcastle, Illa-
warra or Southern, and the Lithgow or
Western field. The coal in all these
fields is of Permo-Carboniferous age and
the strata are divided as follows, in
descending order:

Thickness
in feet.

(1) Upper or Newcastle Coal Measures

with twelve seams of coal varying
from 3 to 25 feet in thickness with
aggregate of 35 to 40 feet work-
able coal. Glossopteris predom-
inates over Gangamopteris. . . 1400-1500

(2) Dempsey series. Fresh water de-

posits without coal 2200

(3) Middle, or Tomago, or East Mait-

land Coal Measures with six

1 Pittman, E. F., The mineral resources of New
South Wales, 1913.

VICTORIA 445

Thickness
in feet.

seams of coal 3 to 7 feet in thickness and aggregating 18 feet of

workable coal 500-1800

(4) Upper Marine series with glacial erratics in shales 6400

(5) Lower or Greta Coal Measures with approximately 20 feet of work-

able coal in two seams, the Upper seam 14 to 32 feet thick and the

Lower seam 3 to 1 1 feet thick. 100- 300

(6) Lower Marine series, containing much igneous rock and beds of glacial

till at base. The rocks of the Carboniferous system are marine
and fresh- water sediments with an abundance of igneous rock, and
in parts of Australia are 20,000 feet thick. They are not coal-bear-
ing.

The Newcastle field has been the most important producer in
the state but many of its collieries are already exhausted. In some
places the mines extend beneath the sea. Some seams have been
intruded with granite which has produced natural coke and nigger-
head coal. In the Illawarra and Lithgow fields the coal occurs in
the Newcastle series. This series is continuous from Newcastle to
Illawarra and again from Sydney westward to Lithgow. At Sydney
Harbor the upper seam is worked at a depth of 2882 feet.

New South Wales contains a large amount of oil shale known in
Australia as kerosene shale and resembling the Torbanite of Scot-
land. The seams occur as lenses, sometimes reaching about a mile
in extent, and from a few inches to about 4 feet in thickness. They
are of Permo- Carboniferous age and the organic matter in them
comes from the spores of plants.

Queensland. This is the second most important state in Aus-
tralia in coal reserves. The coal is almost all bituminous except a
few million tons of semianthracite in the Dawson River field. There
is some lignite, but this is of comparatively little importance. The
coals are mostly of Permo-Carboniferous age, although the bulk of
the coal so far worked is Jura-Trias in age. The Burrum field is
considered to be of Cretaceous age, probably Lower Cretaceous.
The Blair Athol field carries a seam of good clean coal 66 feet thick
at a depth of only 120 feet below the surface. This coal is Permo-
Carboniferous in age.

Victoria. The coal resources of Victoria have not been very
fully determined. There is some bituminous coal of Jurassic age
but the main reserves are in the Miocene brown coal and the thick-

446 THE COAL FIELDS OF THE WORLD AFRICA AND OCEANIA

est seams known occur in this state. At Morwell a bore hole passes
through 780 feet of brown coal in a depth of 1010 feet of strata and
there are three very thick seams running 266, 227 and 166 feet, re-

FIG. 141. Thick series of Coal Measures on coast of New South Wales, at Shep-
herd's Hill. (Photo by E. S. Moore.)

spectively. This coal averages 35.08 per cent water; 29.24 per
cent volatile matter; 33.28 per cent fixed carbon; and 2.40 per cent
ash. It can no doubt be used for briquetting and in gas producers.

WESTERN AUSTRALIA

447

Tasmania. Permo- Carboniferous coal in thin seams and high
in sulphur has been mined a little for domestic purposes in the Mer-
sey and Preolenna coal fields. Most of the coal mined comes from
the Triassic formations which have suffered much faulting and which
have also been much disturbed by intrusions of igneous rock. The
coal is high in ash and it is not used much except for domestic pur-
poses and on some of the railroads. Two collieries are at work
near St Mary's and they together produce about 60,000 tons a year.

Considerable oil shale, known as Tasmanite shale, is found on
the island and it is said to yield 40 to 50 gallons of crude oil per ton.

FIG. 142. Collieries at the state mine, Port Elizabeth, New Zealand. (Photo

by E. S. Moore.)

Western Australia. The only productive field in this state is
the Collie field lying south of Perth. This field is a block of Permo-
Carboniferous measures about 50 square miles in extent. It lies at
quite a shallow depth and is little folded or faulted although surrounded
by faults, one on the southwest having a throw of about 2000 feet.
The coal is friable, non-coking, subbituminous to bituminous in rank
and partly of the splint variety. It has a high moisture content.
The low fuel ratio of the coals in the Collie field is due to the lack
of pressure exerted on these beds even though they occur in for-
mations as old as the Permo-Carboniferous.

448 THE COAL FIELDS OF THE WORLD AFRICA AND OCEANIA

South Australia and Northern Territory. South Australia con-
tains some Jurassic coal in the Leigh's Creek field, and a small
amount has been mined. It is, however, of poor quality. A seam
47 feet thick is said to have been penetrated at a depth of about
1500 feet. In the Great Australian Artesian Water Basin lignite
occurs in the Lower Cretaceous and in the southern part of the state
lignite of Tertiary age occurs in a number of places, but there has
been little exploitation.

The Northern Territory, so far as known, has no important coal
deposit.

New Zealand. 1 New Zealand has inadequate fuel supplies for
her future needs as at the present rate of increase in production her bi-
tuminous coal will be exhausted in less than fifty years. Her main re-
serve lies in the Tertiary brown coals. The seams are notably lenticu-
lar in form and they occur as if deposited around the margins of basins.
There is a little anthracite in the South Island, in the folded and
faulted areas and where the seams have been intruded by igneous
rocks, but the quantity is very small. The geological age of the
coal runs from Jurassic through the Upper Cretaceous and the Ter-
tiary. Possibly there is some lignite of Pleistocene age. The thick-
nesses of some of the seams are as follows: 50 to 60 feet of brown
coal in the Waikato district near Auckland; 53 feet of bituminous
coal in the Buller-Mokihinui district; and 80 feet of lignite in Central
Otago. As stated above, however, the seams are very irregular
in thickness, and they are commonly lenticular in outline.

Antarctica

T. W. E. David 2 , who spent considerable time in Antarctica on
geological work with the Shackleton expedition, states that the coal-
bearing rocks in this great continent may cover something less than
12,000 square miles. Coal has been found at the head of Beard-
more Glacier and at Mackay Glacier, 605 geographical miles Epart.
The coal-bearing area is a long, narrow " horst " bounded by large
faults. As many as six seams with 22 feet of coal have been seen.
The enclosing rocks are believed to be of Permian age and the coals
are therefore related to those of Australia.

1 Marshall, P., Geology of New Zealand, Wellington, N. Z., 1912.

2 Coal Resources of the World.

INDEX

Numbers refer to pages. Illustrations are indicated by an asterisk after page numbers.

Africa: coal fields of, 438; coal resources,

table of, 438; geological age of coals of,

439; map of, 437.
Ala-Kool, algae in, 176.
Alaska: coal fields of, 397; coal resources

of, 400; entry on Coal Lands of, 240;

lignite from, 83;* map of, 399.
Alaskan coals, stratigraphic position of

398.

Alberta, coal in, 343.
Alethopteris serli, 205.*
Algae, 186; ia bogheads, 175.
Alkalies in coal, 37.
Allegheny formation, section of, 367.
Allen, A., 290.

Allen Shaft, Pictou coal field, 341.*
Alliance Breaker, 304.*
Allochthonous, 124, 129.
Ambrite, 102.
American Society for Testing Materials,

44-

Andreaeales, 188.

Andre's rule for shaft pillars, 276.

Andrews, E. B., 128.

Andros, S. O., 305; illustration by, 283.

Angers, 81.

Angiosperms, 184, 185, 206; first appear-
ance of, 213.

Annularia, 198, 193.*

Antarctica, coal deposits in, 448.

Anthracite, 81, 94, 93;* market sizes of,
301; of Keboa., 81; specific gravity of,
4; standards of preparation of, 302;
anthracite mine model, 274;* anthra-
cite mining in Pennsylvania, 277; an-
thracite region of Pennsylvania, 363.

Anthrax, n.

Anthrocoal, 326.

Anticline, 222.

Anticlinorium, 223.

Apparent specific gravity, 7.

Araucarian pines, 211.

Arber, E. A. N., 154, 156.

Arctic islands, coal in, 351.

Arctic tundra, 132.

Argentine Republic, coal in, 405.

Arizona, coal in, 387

Aristotle's Meteorology, 2.

Arkansas: coal in, 385; section of forma-
tions of, 385.

Ash determination, 50.

Ashes: from coal, composition of, 52;
fusibility of, 53, 121; from trees, compo-
sition of, 38.

Ashley, G. H., 89, 95, 147, 148, 255, 262,
370, 378, 381, 382.

Ashley's Use Classification, 118.

Ashmead, D. C., 302; illustration by,
304-

Asia: coal fields of, 429; coal resources,
table of, 430; map of, PI. XVIII.

Asiminia triloba, 157.

Asterophyllites, 198, 193.*

Australia: coal resources of, 443; mining
methods in, 288.

Austria: coal fields of, 423; coal resources
of, 409.

Autochthonous, 124, 129.

Autun, bituminous schists of, 175.

Bacilli, 159.*

Bacteria in coal, 158.*

Bailey, E. G., 43.

Bain, H. F., 263.

Bald cypress, 211.

Balfour, 174.

Barnes, C. R., 186.

Barrier pillars, 273; rule for size of, 275..

449

450

INDEX

Barsch, O., 12.

Bathvillite, 103.

Battery, 279.

Battery breast, 279.*

Baumhauer, E. H. V., 70.

Baxton megaspores, 14.*

Bayley, F., 307.

Beard, J. T., 290.

Beaver, Pa., Quadrangle, structure sec-
tion of, 366.

Bedson, P. P., 21.

Beehive coking, 318.

Beehive ovens, 319.*

Belgian Congo, coal in, 440.

Belgium: coal fields of, 420; coal resources
of, 408; structure section in, 420.

Bell, 220.

Bennettitales, 207.

Bernice Field, 367.

Beroldingen, Franz von, n, 126.

Bertrand, C. E., 12, 174, 175, 176; illus-
tration by, 175.

Bethune, 81.

Bevan, J. P., 168.

"Big" seam at Pocahontas, 376.*

Biochemical process, 158.

Bird, E. H., 320.

"Bird's eye" coal, 94.

Bituminous coal, 87, 85;* photomicro-
graph of, 12; preparation of, 305; spec-
ific gravity of, 4.

Bituminous schists of Autun, 175.

Black Creek seam, photomicrograph of '
coal from, 16.

Black damp, 291.

Black lignite, 84, 86.

Blairmore-Frank region, structure sec-
tion of, 346.

Blandy, J. F., 217.

Blind shaft, 267.

Block longwall system, 284.*

""Blossom," 242.

Blowers, gases from, 25.

Blumenbach, 84.

Bogheads, 87; origin of, 174; phosphor-
ous in, 36.

Bolivia, coal in, 404.

Bomb calorimeter, 72; for sulphur, 59.

Bontchew, G., 425.

Borlkjof, J. C. B., 404.

Borntrager, 20.

Bosnia and Herzegovina; coal fields of,
424; coal resources of, 409.

Botryococcus braunii, 176.

Boulets. 310.

Boulton, W. S., 264.

"Bound" molecules, 21.

Bousquet, G., 407.

Bownocker, J. A., 77, 370.

"Brasses," 34.

Brazil, coal in, 405.

Breaker; cross-section of the Alliance,
304; the Loree, 306.*

Breaking coal at face, 284.

Break-throughs, 270.

Breasts, 267, 271, 278.

British Columbia, coal in, 348.

British North Borneo, coal in, 434.

British thermal unit, (B.t.u.), 71.

Brongniart A., 84, 194, 202.

Brooks, A. H., 397; illustration by, 399.

Brooks, G. S., 312.

Brownsville, Pa., Quadrangle, structure
section of, 366.

Brunton's slope chart, 250.

Brushing down, 269.

Bryales, 188.

Bryophytes, 186, 188.

Buckland, W., 126.

Buffon, L., 126.

Buggy system, 278.

Bulgaria: coal fields of, 425; coal re-
sources of, 408.

Bulman and Redmayne, 264.

Butts, Charles, illustration by, 378.

Bureau of Mines Method of determination
of specific gravity, 5.

Burgess, M. J., 26, 27, 28.

"Buried forests," 138.

Burrell, G. A.. 291, 293.

Byerite, 91.

By-product coking, 320.

By-product derivatives, 323.

By-product tests on various coals, 28.

Byron, T. H., 320.

Cahaba Coal Field, structure section of,
378.

INDEX

451

Caking coal, 87.

Calamarieae, 198.

Calamites, 198, 195,* 194.*

Calcareous concretions, 230.

Calcium in coal, 37.

Calcium oxalate, 20.

California, coal in, 395.

Calorie, 71.

Calorific value: calculated, 79; deter-
mination of, 71.

Calorimeter: standardization of, 77; va-
rious types of .bomb, 72; calorimeter
washings, 75.

" Camel-backs," 220.

Campbell, J R., 306.

Campbell, M. R., 42, 44, 84, 86, 169,
363, 368, 375, 395.

Campbell's classification, 106.

Canada: coal resources of, 339; map of,
PI. XI.

"Candle "coal, 89.

Canmore, Alberta, 347.*

Cannel coal, 87, 89; origin of, 174; photo
micrograph of, 90; specific gravity of,
4, ,

Canneloid, n.

Cape of Good Hope, coal in, 441.

Carbocoal, 326.

Carbon, determination of, 63.

Carbon dioxide, 22, 291.

Carbon-hydrogen ratio and depth, dia
gram of, 167.

Carbonite, 98.*

Carbon monoxide, 22, 292; detector of,
294; effect on animals of, 293. *

Carnegie, Pa., Quadrangle, structure
section of, 366.

Carnot, Ad., 36, 55, 70, 80.

Cellulose, 18.

Cement burning coals, 313.

Central America, coal fields of, 401.

Central Coal Basin rule for shaft pillars,
276.

Ceratizamia mexicana, 37.

Chain pillar, 273.

Chamberlin, R. T., 20, 22.

Chamberlin, T. C , 155.

Chamber longwall, 284.

Chambers, 267, 271.

Chance, H. M., 25

Charbon, 2.

Chemical analysis, 40.

Chemical properties of coal, 18.

Cherry Coal, 87, 88.

Chile, coal in, 406.

China: coal fields of, 431; coal resources

of, 430.

Chlorine in coal, 37.
Choke damp, 291.
Christopher, J. E., 320.
Church, A. H., 86.
Chutes, 278.
Cincinnati arch, 151.
Clanney, 296.
Clark, A. H., 27, 31.
Clark, H. H., 296.
Clark, W. B., 372.
Clarke, F. W., 19, 20.
Classification: difficulties in, 3; of coal

lands, 260; of coals, 105; of plants, 184.
Clay veins, 214, 216, 215.*
Cleats, 8.

Climatic conditions, 155.
Coal: amount derived from peat, 148;

color of, 8; defined, 2; estimate of

quantity in seam of, 258; origin of word,

Coal apples, 229.
Coal balls, 229, 233.
Coalification, second stage of, 160.
Coal Measure plants, composition of, 161.
Coal Miner's Pocketbook, 264.
Coal provinces, 355.
Coemans, E., 196.
Cohen, J. B., 21.
Coke, 88; for domestic fuel, 325; and

coking, 315.
Coke breeze, 323.
Cokedale Mine natural coke, 99.
Coking coal, 30, 87; coking coals, 316.
Col., 2.

Cole, B. A. J., 416.
Coleman, A. P., 157.
Collier, A. J., 385.
Collier's classification, 106.
Colloidal fuel, 314.
Colombia, coal in, 402.
Colorado, coal in, 388.

452

INDEX

Combustion furnace, 63.

Commentry Basin, 36; drifted material

in, 142; fish remains in coal of, 18;

open cut of, 287.*
Competent beds, 170, 223.
Composition of wood, peat, and coals, 96.
Concretions in coal, 229.
" Condensed " gases, 26.
Conemaugh formation, section of, 368.
Coniferales, 211.
Connellsville basin coke, 99.
Connellsville coal tested, 28.
Constance, Lake, peat on, 147.
Contiguous seams, working of, 280.*
Contorted partings, 224.
Contours, structural and surface, 248.*
Coppee oven, 320.

Cordaitales, 208, 209;* in Devonian, 182.
Cost of mining, average, per ton, 257.
Coulter, J. M., 186.
Cowles, H. C., 1 86.
Crane, W. R., 384; illustration by, 83,

100, 223.

Critical level, 136.
Cross and Bevan, 161.
Cross-cuts, 270; cross-entries, 269.
Crowsnest coal area, map of, 345.
Cryptogamic plants, spores of, 9.
Curtis^ H. A., 326.
Cut-out, 214; 215;* on Des Moines River,

216.

Cut-throughs, 273.
Cycadales, 207.
Cycadeoidea marshiana, 208.*
Cycadofilicales, 206.
Cycadofilices, 203.
Cycads, Age of, 184, 208.

Dakotas, coal fields of, 393.
Dalburg, F. A., 435.
Dana, E. S., 2, 3, 89, 91.
Daubr'e, A., 101, 166.
David, T. W. E., 156, 448.
Davis, C. A., 131.
Davy, Sir William, 296.
Dawson, J. W., 12, 174, 209.
"Debris," n.
Defline, M., 416.
Degousee, M. J., 140.

De la Becke, 166.

De Lisle, 87.

Delta deposits, coal in, 139.

Denmark: coal fields, of 421; coal re-
sources of, 408.

Denoel, L., 420.

DePapp, C., 424.

Depth: maximum of coal mines in foreign
countries, 253; maximum, of coal mines
in the United States, 251; of burial,
166; of seam, determination of, 247;
table for determination of, 249.

Derivatives of coal and their uses,

Fig- 5.

Descloizeaux, A., 97.
Devonian period, first appearance of land

plants in, 179.
Diatoms, 86.
Dike, 228,* 231.*
Diller, J. S., 396.
Dip, 221.*
Dismal Swamp, 139,* 141,* 142;* Lake

Drummond in, 137;* map of, 135;

peat in, 137.

Displacement in fault, 225.
Distillation, products of, 25.
Domestic anthracite, preparation of, 300.
Dominian, L., 425.
Dopplerite, 83.
Dorrance, C., 310.
Double battery breast, 279.*
Double room, 272.*
Douglas, E. A., 435.
Dowling, D. B., 339, 348; classification

by, 112; illustration by, 345, 346.
Drake, N. F., 431.
Drift, 266.

Drifted vegetation, 139.
Drills in prospecting, 243.
Dron's rule for shaft pillars, 275.
Dry coal, 92.
Dulong's formula. 79.
Dumble, E. T., 99, 386.
Duncan, W. G., 291.
Dunkard formation, section of, 370.
Dunkley, W. A., 312.
Durley, R. J, 7, 8, 339.
Dutch East Indies, coal in, 435.
Duxite, 103.

INDEX

453

Dyer, B., 68.
Dysodile, 86.

Eastern-Middle Anthracite field, section
through, 362.

Ecuador, coal in, 404.

Electric cap lamp, 296.

England: coal resources of, 408; resources
of various coal fields in, 412.

Entries, 263, 270.

Equisetales, 190, 198.

Equisetum, 198.

Eschka method for sulphur, 56

Eshereck, George, Jr., 327.

Ethane in coal, 20.

Europe: coal fields of, 407; coal resources,
table of, 408; map of, PL XVI; min-
ing methods in, 287; geological age of
coals of, 410.

Evans, J. W., 434.

Exposure before burial, 162.

Face, 271.

Face on, 272.

Falkenau, brown coal of, 20.

Fat coal, 92.

Fats, composition of, 20.

Faults, 224, 225,* 226.

Fayol, H., 32, 129, 141, 162.

Federal Trade Commission Report, 257.

Ferns, 180, 201,

Fieldner, A. C., 44, 52, 70, 73

Filicales; see Ferns.

Finn, C. P., 21.

Fire damp, 22, 294.

First mining in Virginia, i.

First production in the United States, i.

Fish remains in coal, 18.

Fisher, C. A., 251.

Fixed carbon, determination of, 56

Flow, igneous, 229.

Flow sheet of Alliance Breaker, 303.

Fontaine, W. M., 184, 193; and White,

illustration by, 204.
"Fool's gold," 34.
Foot-acre, value of, 255.
Formula for composition of coals, 149.
Fossil flora of coal-forming periods, 178.
Foster's rule for shaft pillars, 276.

Foundry coke, standard for, 316.

Fracture in coal, 8.

France: coal fields of, 416; coal resources

of, 408.

Frank, Alberta, landslide, 344.*
Franke, G., 309.
Frazer, J. C. W, 31.
Frazer, T., 306.
Frazer's classification, 105.
"Free" paraffins, 21.
Fremy, E., 30.
Fresh water swamps, 133.
Fuel ratios of Pennsylvania coals, map

of, 172

Fundamental matter, n.
Fungi, 1 86; in coal, 159.
Fusain, 100, 307.
Fusibility: of ash, 121; of various coal

ashes, 53.

Gagates, 2, 97.

Gamba, F. P., 402.

Gangamopteris, 180; 211.*

Gangamopteris flora, 156.

Gangways, 267, 278.

Garcia, J. A., 290.

Gardner, J. H., 387.

Gas manufacture: bibliography, cited,
25; coals for, 311.

Gases: evolved from coal below tempera-
ture of decomposition, 23; in coal, 22.

Geikie, A., 147.

Geographic distribution of coal, 328.

Geological age of coals: of Africa, 439;
of Europe, 410; of North America,
table of, 338; of Oceania, 443; of the
United States, 360.

Geological distribution of coal, 328; by
varieties, table of, 332.

Geological formations, table of, 330

Georgia, coal in, 378.

Germany: coal fields of, 421; coal re-
sources of, 409.

Gibson, 378.

Gingkoales, 210; ancestors of, 182.

Glanzkohle, 94

Glossopteris, 180, 211.*

Glossopteris flora, 156, 157.

Gob side, 272.

454

INDEX

Gore, N. Z., retinite from, 102.

Gottlieb, table by, 161.

Gouge, 225.

Goutal, M., 79.

Goutal's curve, 80.

Grains, cones, spores, 181.*

Grains from Coal Measures, 185.*

Grande Couche, 36, 214.

Grand'Eury, F. C., 128, 191, 203; illus
tration by, 150, 181, 185, 209.

Graphic method for thickness, 244.

Great Britain; coal fields of, 407; coal re-
sources of, 408.

Greece: coal fields of, 425; coal resources
of, 408.

Gresley, W. S., 130.

Grinding thin sections, 15.

Grout's classification, 109.

Gruner, E., 407; classification by, 115.

Gr Liner, L., 128.

Guignet, E. 30.

Gulf Province, 385.

Giimbel, C. W., von, 12, 128.

Gymnosperms, 185, 206; ancient types of,
203; dominant in Triassic, 182.

Gypsum in coal, 35.

Hade, 225.
Hadley, H. F., 31.
"Half on," 272.
Hall, A. A., 21.
Hall, R. D., 36.
Hamilton, N. D., 309.
Hapke, L., 32.
Hard coal, 94.
Hardness, 8.

Harper, Francis, illustration by, 133, 134.
Harrisburg, 111., coal tested, 28.
Haulage, 288; electric, 290.*
Hausmann, J. F. L., 84, 87.
Hauy, 94.

Hazeltine, illustration by, 373.
Hazleton, Pa., district, 95; structure sec-
tion of, 362.
Hawes, G. W., 161.
Hayden, H. H., 433.
Hayes, C. W., 378.
Headings, 267.
Heat, effects of, 168.

Heave, 225.

Heavy solutions for determination of
specific gravity, 7.

Heinrich, O. J., 101.

Hepaticae, 188.

Hilaire, B. S., 2.

Hill, R. T., 400.

Hillman Coal and Coke Co., illustration
by, 292, 319.

Hinds, H., 382, 383.

History of first uses of coal, i.

Hochstetter, 102.

Hoffman, E. J., 31.

Hogarth's flask, determination of specific
gravity by, 5.*

Hoisting, 289.

Holmes, J. A., 42.

Horn Coal, 89.

Horsebacks, 214, 216, 215;* on mine map,
218.

Horsetails, 190; silica in, 37.

Houille, 86, 87.

Howarth, 384.

Ho well, S. P., 298.

Howley, J. P., 352.

Hughes' rule for shaft pillars, 276.

Humboldtine, 20.

Humic coals, 87.

Humus acids, 20.

Hungary: coal fields of, 424; coal re-
sources of, 409.

Hutchinson R. P., illustration by, 300,
306.

Hutton, W., 11, 174.

Huxley, 174.

Hydrogen, 295 ; determination of, 63.

Hydrogen sulphide, 295.

Hydrogenous coals, 90.

Hydroxide of sodium for softening sec-
tions, 13.

Igneous intrusions, 228.*

Illinois: coal in, 381; section of Coal

Measures of, 380
Illuminating gas, 312.
Inby, 271.

Incompetent beds, 170.
India: coal fields of, 433; coal resources

of, 431-

INDEX

455

Indian Lands, 240.

Indiana, coal in, 382.

Inert volatile matter, no.

In situ theory, 124.

Interior province, 379.

International Geological Congress, classifi-
cation by, 113.

lonite, 104.

Iowa: cross-section of formations of, 382;
coal in, 382.

Ireland: coal fields of, 416; coal resources
of, 408; peat in, 133.

Iron in coal, 37.

Iso-anthracitic lines, 173, 174; of South
Wales field, 165.

Isoclinal fold, 222.

Isovols, 174.

Italy: coal fields of, 419; coal resources
of, 408.

Ivanov S. L., analysis by, 177.

Japan: coal fields of, 432; coal resources

of, 430.
Jeffrey, E. C., 12, 13, 101, 130, 174, 176,

233; illustration by, 90.
Jet, 97.
John, von, 20.
Johnson, W. R., 105.
Johnston, F. W., 103.
Jones, D. T., 21.
Joseph, 1 66.
Jukes, J. B., 127; illustration by, 229.

Kansas: coal deposits in, 384; structure

section of Coal Measures of, 384.
Karst, 84, 94.
Katz, S. H., 23.
Katzer, F., 424.
Kauri gum, 102.
Kaustobioliths, 130.
Kelley, W. P, 38.
Kentucky cannel, 90.
Kentucky, coal in, 377.
Kerosene shale, 175.
"Kettle," 220.
Kick, J. J., 196.
Kidston, 203.
Kilkenny coal, 89.
Kinosuke, I., 431, 432.

Kirwin, R., 89.

Kjeldahl-Gunning method, 68.

Klonne oven, 322.

Koppers byproduct coke plant, 324.*

Korea, coal in, 432.

Krafft, 20.

Kressman, F. W., 32, 308.

Le Conte J., 127.

Laccolith, 228.

Land Office Regulations, 238.

Land plants, rise of, 180.

Lane, A. C., 379.

La Veta, Colorado, structure section near,

388.

Law of Hill, 1 66.
Laws governing prospecting, 238.
Leaf cushions, 192.
Leaf traces of Sigillaria, 194.
Leasing laws, 240.
Lenhart, L. R., 52.

Lepidodendron, 157, 180, 191; 179,* 183.*
Lesher, C. E., 51.
Lesley, J. P., 128.
Lesquereaux, illustration by, 191, 193, 195,

197, 200, 202.
Lignite, 84; ignition temperature of, 32;

85;* seam of, 394;* specific gravity of,

Lignocellulose, 18.

Liguria, 2.

Link, F., n, 126.

Locating new seams, 242.

Loew, O., 104.

Logan, W. E., 126.

Loire basin coals, 31.

Lonchopteris bricei, 206.*

"Long horn," 272.

Longwall, development in anthracite re-
gion, 285.*

Longwall method, 281.

Longwall mine, 282,* 283.*

Lord, N. W., 73, 77, 87.

Loree Breaker, 306.*

Lump anthracite, 301.

Luster, 9.

Lyburn, E., 416.

Lycia, jet from, 2.

Lycopodium, 190.

INDEX

Lycopods, 180.
Lyes, 271.

MacCulloch, J., 126.

McCalley, 378.

McCallie, 378.

McConnell, W., 23, 24.

McCreeth, A. S., 106.

Macklin, J. F., illustration by, 290.

Madura arantiaca, 157.

Macrosporangia, 207.

Magnesium in coal, 37.

Mallett, E. J., 91.

Maly, 102.

Manchuria: coal fields of, 432; coal re-
sources of, 431.

Mangrove swamp, N. Z., 144.*

Mangrove swamps, 138.

Manitoba, coal, in 343.

Map of: Africa, 437; Alaska, 399; Asia,
PI. XVIII; Canada, PI. XI; European
Russia, 427; Oceania, PI. XX; South
America, 403; United States, PI. XII;
Western Europe, PI. XVI.

Marcasite, 34.

Mariotte flask, 65.

Marsh gas, 294.

Marshall, P., 448.

Marshes, 132.

Martin, G. C., 397.

Maryland, deposits in, 372.

Marzec, L., 424.

Maumen?, J., 71.

Mellite, 20.

Merrimac Mine Breaker, 376.*

Metagami River timber, 145.*

Methane, 22, 294; absorbed by coal, 23.

Methyl orange indicator, 75.

Mexico, coal in, 400.

Meyer, von, 24.

Michado, M. R., 406.

Michigan: coal in, 379; structure section

in, 379-

Micrococcus, 159.
Microscope in study of coal, 9, n.
Middletonite, 103.
Mietzsch, H., 128, 138, 154.
Miller, B. L., 402.
Miller, C. F., 38.

Mills, J. E., 310.

Milojkovitch, F. A., 424.

Mine fires, 298.

Mine gases, 290; relation of, to volatile

constituents, 25.
Mine level, 270.
Mine ventilation, 296.
Mineral charcoal, 100.
Mineral coal, 2.

Mineral constituents of coal, 33.
Mineral, defined by Dana, 3.
Mineral Industry, cited, 321, 335.
Mineral Lands, 3, 238.
Mineral Resources United States Geological

Survey, cited, i, 255, 299, 353.
Minimum thickness of seams mined, 253.
Mining Engineering rule for shaft pillars,

276.

Mining machine undercutting ream, 289.*
Mining machines, 286.
Mining methods in foreign countries, 287.
Mining of coal, 264.
Missouri, coal in, 383.
Mitscherlich, A., 70.
Moffat, E. S., 164.
Mohr, F., 145.
Moh's scale, 8, 95.
Moissan, H., 32, 86.
Moisture, determination of, 49.
Moisture oven, 49.
Monoclinal fold, 222.
Monongahela formation, section of, 369.
Montana, coal in, 394.
Montenegro, 425.
Moore, E. S., 217; illustration by, 144,

145, 148, 152, 227, 231, 236, 265, 287,

344, 351, 417, 446, 447.
Morwell, Australia, 214.
"Mother-of-coal," 100.
Mourlot, A., 39.
Mud-screen product, 301.
Muer, H. F., 60
"Mur," 153.
Murchison, R. L, 127.
Musci, 1 88.

Naked seeds, 206.
Naphthenes, 21.
Natal, coal in, 447.

INDEX

457

National Parks, 240.
Natural coke, 98.*
Neck, 271.

Netherlands: coal fields of, 420; coal re-
sources of, 408.
Neuropteris, 201,* 202.*
Neuss, 84.

New Brunswick, coal in, 342.
New Mexico, coal in, 387.
New South Wales, coal in, 444; section

through main coal basin of, 444.
New Zealand: coal fields of, 448; coal

resources of, 443.
Newberry, J. S., 128, 196.
Newfoundland, coal in, 352.
Niggerhead coal, 230, 235; analyses of,

237, 236.*

Nitchie, C. C.. 312.
Nitric acid, effects of, on coal, 30.
Nitrogen determination of, 68.
Non-caking coal, 88.
Non-coking coal, 88.
Normal fault, 225.
Norris, R. V., 307.
North America: coal fields of, 336; coal

resources of, 337; geological age of

coals of, 338.

North Dakota lignite, 85.*
Northern Anthracite field, section through,

362.

Northern Great Plains Province, 387.
Northern Territory, Australia, coal in,

448.

Northrup, H. B., analyses by, 102.
Northwest Territories, coal in, 351.
Nova Scotia, coal in, 340.
Norway, coal in, 428.

Oak, composition of, 162.

Oberfell, G. G., 291.

Occluded gases in coal, 22.

Oceania: coal fields of, 438, 442; coal
resources, table of, 443; geological ages
of coals of, 443 ; map of, PI. XX.

Odell, W. W., 312.

Odontopteris, 200.*

Ohio: coal in, 370; section of Carbonifer-
ous formations of, 373.

Oils, composition of, 20.

Okefinokee Swamp, 133,* 134.*

Oklahoma, coal in, 385.

Oleinic acid, 177.

Oliver, F. W., 203, 204.

Ombre de Cologne, 86.

Ontario, coal in, 342.

Ophioglossales, 190.

Oregon: coal in, 396.

Organic acids, salts of, 20.

Origin of coal, 123.

Osbon, C. C., 136.

Otto-Hilgenstock oven, 322.

Otto-Hoffman oven, 322.

Outby, 271.

Overthrust fold, 222.

Ovitz, F. K., 22, 25, 26, 27, 28, 33, 309.

Oxalic acid, 20.

Oxygen, determination of, 70.

Oxypicric acid, 30.

Pacific Coast Province, 395.

Packs; gob, 282; road, 282.

Pack-walls, 282.

Panel system, 277.*

"Paper coals" of Russia, 20.

Paraffin series, 20.

Parmelee, C. W., 313.

Parr, S. W., 31, 32, 42, 43, 52, 60, 62, 70,
79, 149, 308, 309; classification by, 109;
peroxide bomb calorimeter of, 67.

Parrot coal, 89.

Partings, 214, 215.*

Pas-de-Calais coal basin, complicated struc-
ture in, 232.*

Peacock coal, 96.

Peat, 82; rate of accumulation of, 146.

Peat-bogs, 131.

Pebbles of coal in Coal Measures, 164.

Pechkohle, 86.

Pecopteris, 199.*

Peek's Handbook, 264, 300.

Pennsylvania, 81; bituminous region of,
368; coal fields of, 363; structure sec-
tion through southwestern part of, 366.

Pennsylvania anthracite: distribution of
in 1917, 299; specific gravity of, 96.

Pennsylvania bituminous coal, distribu-
tion of in 1917, 299.

Permissible explosives, 298.

458

INDEX

Permo-Carboniferous section in New South

Wales, 157, 444.
Persia: coal fields of, 434; coal resources

of, 431.

Peru, coal'in, 404.
Petrascheck, W., 423.
Phanerogams, 206.
Phenol as solvent for coal, 31.
Philippine Islands, coal in, 435
Phillips, W. B., 386.
Phosphorous, 36; determination of, in

coal ash, 53.

Photometric method for sulphur, 60.
Photomicrographs of coal, 16; from Roy-

alston showing spores and woody tissue,

10; showing pyrite, 35; showing resin,

19; showing spores in cannel, 90.
Phylloglossum, 190.
Physical constitution, 9.
Physical properties, 4.
Pila bibractensis, 175.*
Pillar drawing, 280
Pillar-and-stall system, 276.
Pillars, size of, 273.
Pinaceae, 211.
Pinches, 215.
Pines, see Pinaceae.
Pinnularia, 198.
Pishel, M. A., 88.
Pitch, 222.
Pittman, E. F., 444.
Pittsburgh seam, 369, 371, 372, 374, 375;

photomicrograph of coal from, 16.
Plan of four-entry mine, 268.
Plankton algae, 177.
Plant spores used in distinguishing seams,

17-

Pliny, 2.

Pocahontas coal tested, 28.

Pocahontas field, 375.

Poland, coal in, 426.

Pollard, W., 7, 48, 63, 65, 69, 107, 166, 173.

Pope, G. S., 43-

Port Elizabeth, N. Z., collieries of, 447.*

Porter, coal of, 81.

Porter, H. C., 22, 25, 26, 27, 28, 33, 309.

Porter, J. B, 7, 8, 339.

Protugal: coal fields of, 418; coal re-
sources of, 408.

"Pot", 220.

Potonie, H., 12, 90, 130, 138.
Pottsville formation, section of, 367
Powdered fuel, 313.
Powell, A. R., 62, 317.
Power, F. Danvers, 288, 442.
Preparation of coal, 299.
Pressure, effect of, on coal, 170.
Prestwich, J., 97.
Price of coal at mine, 256.
Producer gas, 311.

Production of world in 1913, i; by coun-
tries, 335; and states, 352.
Prospecting for coal, 238.
Proximate analysis, 48.
Psilo tales, 190.
Pteridophytes, 186, 188.
Pycnometer, 4.
Pyridine, 32.
Pyrite, 34.
Pyroretinite, 104.

Queensland, coal in, 445.

Rabino, H. L., 434.

Ranks of coal, 82.

Rath, G. von, analyses by, 99.

Reinchia australis, 176.

Renault B., 12, 148, 149, 174, 175, 196, 198,

207; illustration by, 158, 159, 210.
Renier, A., 420.
Resinous substances, 102.
Resins: composition of, 20; in coal, n.
Resources of world by continents, 333.
Retinite, 102.
Rhacopteris, 180, 211.*
Rhode Island: anthracite of, 95; coal in,

370-

Rhodesia, coal in, 440.
Rib, 271.

Rice, G. S., 287, 297.
Richardson, G. B., illustration by, 388,

389-
Ries, H., 172; illustration by, 341, 342,

347, 376, 394-
Riffle sampler, 46.
Rittman, W. F., 25.
Roberts oven, 322.
Robertson, I. W., 291, 293.

INDEX

459

Robinson, W. O., 38.

Rock chutes, 280.

Rock Springs coal field, structure section
of, 392.

Rocky Mountain Province, 387.

Roden, J., 434.

Rogers, H. D., 90, 92, 101, 127.

Rolls, 214, 216, 215,* 234.*

Ronchamp, 81

Rooms, 267, 271; inclined, 271.*

Room-and-pillar method, 264, 267.

Royal Commission on Coal supplies, 253.

Royalston, 111., photomicrograph of coal
from, 10.

Royalties on leases, 259.

Roumania: coal fields of, 424; coal re-
sources of, 409.

Russia: coal fields of, 426; coal resources
of, 409; in Europe, map of, 427.

St. tienne: fault at, 227;* tree trunks
near, 148,* 152.*

Ste. Colombe sur 1'Hero, 97.

Saar basin, section through, 422.

Safety lamps, 295.

Salisbury, R. D., 155.

Sampling, 40; English method of, 48;
equipment for, 42; in laboratory, 47;
laboratory apparatus for, 46; standard
method of, 44.

San Raphael, 39.

Sapropelic coals, 90.

Sapropelic deposits, 130.

Sargasso Sea, 145.

Saskatchewan, coal in, 343.

Schering's celloidin, 13.

Schrotter, 104.

Schulze, Franz, n.

Schwarzkohle, 87.

Scotland- coal fields of, 413; coal re-
sources of, 408.

Scott, D. H., 203, 204.

Scouring rushes, 198.

"Seatearth," 153.

Seibert, F. M., 293.

Selvage, 225.

Selvig,W A, 52.

Semet-Solvay coke pusher, 321.*

Semet-Solvay plant, 322.*

Semianthracite, 92.

Semibituminous coal, 92.

Sequoia, 211.

Serbia: coal fields of, 424; coal resources

of, 409.

Seyler's classification, 107.
Shaft, 266, 267.
Shaft bottom, 292.*
Shaft pillar, 273.
Shaler, N. S, 135, 375; illustration by,

i35, 137, 139, Ui, 142.
Shamel Charles, 238.
Shepherd's Hill, New South Wales, 446.*
Sheppard, S. E., 314.
Sheridan coal tested, 28.
Shoofly, 271.
"Short horn," 272.
Shove fault, 226.

Shultz and Lewis, illustration by, 392.
Siberia, coal in, 431.
Sidings, 271.
Sigillaria, 180, 194, 187.*
Sigillarian cones, 195.
Sigillariostrobus goldenbergi, 189.*
Silica in coal, 37.
Sill, 228.

Singewald, J. T., Jr., 402.
Sinnatt, F. S., 307.
Stele, 190.

Slate pickers in breaker, 300 . *
Slickenside, 225.
Slip fault, 226.
Slope, 266.
Smith, G. O., 395.
Smith process, 327.
Smithing coals, 313.
"Sole," 153.

Solms-Laubach, 193, 198.
Solubility of coal, 29; relation of, to

coking, 30.

Somermeier, E. E., 77.
Somme Valley, peat in, 147.
Sorus, 189.

South Africa, Union of, coal in, 441.
South America, coal fields of, 402; map

of, 403

South Australia, coal in. 448
South Wales: coal in, 414; origin of coals

of, 1 68.

460

INDEX

South Wales field, diagram of ash and
carbon-hydrogen ratios of coal of, 173.

Southern Nigeria, coal in, 439.

Spain, coal fields of, 418; coal resources
of, 408.

Specific gravity: defined, 4; of anthracite
4; of "ash-free" and "moisture-free"
specimens, 7; of bituminous coal, 4;
of cannel, 4; of lignite, 4; relation of,
to quality of coal, 8.

Specific gravity, determination of: by
Bureau of Mines, 5; by heavy solutions,
7; by Hogarth-flask, 5; by hydrometer
method, 6; by pycnometer, 4.

Spermatophytes, 185, 186, 206.

Sperr, F. W., Jr., 320.

Sphagnum 132, 188.

Sphenophyllales, 196.

Sphenophyllum, 190.

Sphenopteris, 197.*

Spitzbergen: coal fields of, 428; coal re-
sources of, 409.

Splint coal, 87, 88.

Split, 215.*

Split-volatile ratio, 112.

Spontaneous combustion, 307; chemical
causes of, 32.

Spruces, 211.

Square-chamber method, 287.

Squeezes, 214, 215.

Standardization of calorimeter, 77.

Stansfield, E., 32, 326.

Stanton, F. M., 5, 44, 73.

Steam coals, 314.

Steinkohle, 2

Stemkoenig, L. A., 38.

Stephenson, George, 296.

Sterling, Paul, 300.

Stern, H., 307.

Stevenson, J. J., 124, 128, 129, 138; illus-
tration by, 369, 370.

Stigmaria, 130, 153, 193; S. ficoides, 196;
S. ficoides, 191.*

Stink damp, 295.

Stock, H. H., 96, 363; illustration by
278, 280, 362.

Stohman's solution, 76.

Stone coal, 94.

Stone damp, 295.

Stopes, M. C., 230.

Storage, 306; deterioration of coal in, 309

Storrs, L. S., 387.

Stout, D. A., 237.

Strahan, A., 7, 107, 166, 173, 407; illus-
tration by, 224; and Pollard, diagram
by, 165, 167.

Streak, 8, 9.

Streptococcus, 159.

Strike, 221.*

Stringer of coal, 221.*

Stripping Mammoth seam, 265.*

Stripping method, 264.

Structural contours, 248.

Structural features of coal seams, 214.

Stumps in Coal Measures, 150.*

Stur, D., 192.

Subbituminous coal, 84, 86, 93.*

Succinite, 103.

Sullivan Machine Co., illustration by, 289.

Sulphates in coal, 34.

Sulphides in coal, 34.

Sulphur, 33; determination of, by Eschka
method, 56; in ash, 62; in coke, 33,
316; inorganic, 34; organic, 35.

Sulphur balls, 34, 230.

Sulphur diamonds, 34.

Sulphuretted hydrogen, 295.

Sulphurous gases, 27.

Sumatra Swamp, 138.

Summit Hill, 95.

Superbituminous coal, 92.

Sussmilch, C. A., 156, 210.

Sweden: coal fields of, 428; coal resources
of, 409.

Swells, 214, 215.

Swift, illustration by, 282.

Switzerland, coal in, 419.

Syncline: at Hazleton, 236;* pitching,

222.*

Synclinorium, 223.

System of Mineralogy, Dana's 2.

Taeniopteris Newberriana, 204.*

Taff, J. A., 98, 385-

Tantalus Mine on Yukon River, 351.*

Tasmania, coal in, 447.

Tasmanite shale, 447.

Tauber's drying apparatus, 66.

INDEX

461

Taxaceae, 211.

Taylor, C. A., 70.

Temperature, effect on constituents,

evolved, 26.
Tennessee, coal in, 378.
Terre d'ombre, 86
Texas, coal in, 386.
Thallophytes, 186, 188.
Theophrastus, 2.
Thick seams: bench working in, 288;*

mining in, 284.

Thickening of seams in anticlines, 223.
Thickest seam in world, 214.
Thickness of formation: determination

of, 245; curve for graphic determination

of, 246.
Theissen, R., 9, n, 13, 14, 15, 20, 34,36,

101, 130, 176; illustration by, 10, 12, 14,

16, 19, 35-
Thin seams: mined in foreign countries,

255 ; mined in United States, table of, 254.
Thin sections, preparation of, 12.
Thomas, J. W., 23, 24.
Thracius lapis, 2.
Throw, 225.
Thrust fault, 225.
Tile burning coals, 313.
Time since burial, 163.
Topographic conditions in coal-forming

periods, 150.
Torbanite, 87, 91.

Toronto, Canada, glacial deposits, 157.
" Tortoises" 220.
Transformation of vegetal matter to coal,

157-

Transportation theory, 125.
Transvaal, coal in, 441.
Tree trunks in Coal Measures at St.

tienne, 148,* 152.*
Trees, composition of, 161.
Trescot, T. C., 68.

Trinidad, Colorado, section near, 389.
Trinkerite, 104.

Tri-radiate lines in spores, 14.*
Tschernyschew, Th, 426.
Tunnel, 266.

Turbidimeter, Jackson's candle, 60.
Turkey, coal in, 425.
Turn-out, 271.

Ultimate analysis, 63.

Unconformity, 227.

Underclays, origin of, 153.

Underground work, 264.

Uniontown, Pa., Quadrangle, structure
section of, 366.

United States: coal in, 352; coal produc-
tion of, 352, 353, 354; distribution of
coal of, by kinds, 355; geological age
of coal formations of, 360; map of,
PI. XII; table of coal resources of, 357,
358, 359-

Upthrow side, of fault, 226.

Uses of coal, 299.

Utah: coal in, 391; coal of, tested, 28.

Value of world's production in 1913, i.
Valuation of coal lands, 238, 250.
Vanadium in coal, 39.
Vandalia, Ind., photomicrograph of coal

from, 19.

Varieties of coal, 82.
Vascular cryptogams, 180, 182.
Venezuela, coal in, 404.
Venice, Gulf of, peat in, 140.
Victoria, coal in, 445.
Vignon, Leo, 30, 88.

Virginia: coal in, 375; first mining in, i.
Volatile constituents, escape of, from seam,

169.
Volatile matter: determination of, 54;

furnace for determination of, 54.*
Voltzia, 182.

Walchia, 182, 213; W. frondosa, 210.*

Wales, coal resources of, 408, 412.

WaUerius, J. G., 84.

Walsen Mine, natural coke of, 99.

Washington, coal in, 396.

Water gas, 312.

Watson, D. M. S., 230.

Waxes, composition of, 20.

Wedemeyer, K., 68.

Weight of coal in foot-acre, 258.

Welsh anthracite, specific gravity of, 96.

Welsh coals, tests on, 24.

West Indies, coal fields of, 401.

West Virginia, coal in, 372.

Western Australia, coal in, 447.

462

INDEX

Wheeler, R. V., 21, 27, 28, 31, 32.

Wheelerite, 104.

Whewellite, 20.

Whitaker, M, C., 25.

White, D., ii, 12, 14, 20, 33, 88, 101, 102,
130, 156, 166, 170, 176, 195, .196, 203,
368; illustration by, 367.

White, I. C., 193, 372, 405; illustration by,
367, 368.

White damp, 292.

White's classification, in.

Wieland, G. R., 207; illustration by, 208.

Wilder F., illustration by, 394.

Wilkes-Barre, Pa., structure section at, 362.

Willputte oven, 322.

Witham, H., n, 126.

Wood: changed to coal, 164; composi-
tion of, 19.

Woodworth, J. B., 375.

Worrell, S. H., 386.

Wright, C. L., 311.
Wyoming basin, Pa., 171.
Wyoming, coal in, 392.

Xyloid lignites, solubility of, 29.
Xyloid material, 9.
Xylon, n.

Yancey, H. J., 306.

Yorkshire jet, 97.

Yukon Territory, coal in, 350.

Zalessky, M. D., 176, 235.

Zamia, 207.

Zamites, 207.

Zeiller, R., 190, 195, 202, 203, 204, 207;

illustration by, 179, 183, 187, 189, 194,

199, 201, 205, 206.
Zern, E. N., 315, 363.

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