xt79cn6xz88z https://exploreuk.uky.edu/dips/xt79cn6xz88z/data/mets.xml  Hotchkiss, Willard E. 1939 Other contributors: National Research Project on Reemployment Opportunities and Recent Changes in Industrial Techniques (U.S.); United States. Bureau of Mines. 2 v. (xxx, 436 p.) : ill., maps ; 26 cm. Mineral technology and output per man studies ; report no. E-9. Part of the Bert T. Combs Appalachian Collection. UK holds archival copy for ASERL Collaborative Federal Depository Program libraries. Call number FW 4.7:E-9. books  English Philadelphia, Pa. : Work Projects Administration, National Research Project in cooperation with Dept. of the Interior, Bureau of Mines This digital resource may be freely searched and displayed in accordance with U. S. copyright laws. Maryland Works Progress Administration Publications Mechanization, Employment, and Output Per Man in Bituminous-Coal Mining- Vol. 1 by Willard E. Hotchkiss [et al.] text Mechanization, Employment, and Output Per Man in Bituminous-Coal Mining- Vol. 1 by Willard E. Hotchkiss [et al.] 1939 1939 2015 true xt79cn6xz88z section xt79cn6xz88z g   V V  _ . l,. V7, ,  ·  Y _- A , _   ..   I , , - , , ,, , v , 1-· » ,,I *   -.   ·é .,,r;,;·. 2 ; .;.·.·L.,;; Z-.: L,-H,   #1-.. ;·¤.;,1.,..,=;»,, ,, I1 is 
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F. C. HARRINGTON CORRINGTON GILL lg
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Reemployment Opportunities and Recent Changes A·§
in Industrial Techniques, _ g
- DAVID WEINTRAUB ` _ g
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UNITED STATES DEPARTMENT OF THE INTERIOR id
BUREAU OF MINES Ԥ
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JOHN W. FINCH, Director  
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  MECHANIZATION, EMPLOYMENT, AND OUTPUT PER MAN I
IN BITUMINOUS—COAL MINING  
 
Willard E. Hotchkiss,  
F. G. Tryon, Charlotte K. Warner, L. N. Plein, Walter   Dake, J?
R. L. Anderson, J. J. Gallagher, and Margaret H. Schoenfeld §
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VOLUME I lg
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·-__ wURx PROJECTS ADMINISTRATION, NATIONAL RESEARCH 1=•R0.IEcT  
  In cooperation with  
A DEPARTMENT or THE INTERIOR, BUREAU or MINES  
· Report No. E—<;  
Philadelybhia, Pennsylvania  
1
August IQBQ  
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  THE WPA NATIONAL RESEARCH PROJECT `·
  ON REEMPLOYMENT OPPORTUNITIES AND RECENT CHANGES
  IN INDUSTRIAL TECHNIQUES
 
  Under the authority granted by the President In the Execu-
5 _ tive Order which created the works Progress Administration,
it Administrator Har-ry L. Hopkins authorized the establishment
  »_ of a research program for the purpose of collecting and ana-
ix 2 lyzlng data bearing on problems of employment, unemployment,
i and relief. Accordingly, the Natlonal Research Program was {
i I established In October 1935under the supervision of Corring ton
ig Gill, Assistant Administrator of the WPA, who appointed the
§· directors of the individual studies or projects. .
  " The Project on Reemployment Opportunities and Recent Changes
gx ·` ln Industrial Techniques was organized in December 1955 to
gx inquire, with the cooperation of lndustry, labor, and govern-
mental and private agencies, into the extent of recent changes
Y. , ln industrial technlques and to evaluate the effects of these
~ changes on the volume of employment and unemployment. David
- Weintraub and Irving Kaplan, members of the research staff
1_ of the Dlvlsion of Research, Statistics, and Finance, were ap-
DOIHEGCI, respectively, Director and Associate Director ofthe `
Project. The task set for them was to assemble andorganize
the existing data which bear on the problem and to augment `
these data by field surveys and analyses. ·
` To this end, many governmental agencies which are the col-
lectors and repositories of pertinent information were ln-
§ ‘ vlted to cooperate. The cooperating agencies of the United
t States Government include the Department of Agriculture, the
Q Bureau of Mines ofthe Department of the Interior, the Bureau
~. of Labor Statistics of the Department of Labor, the Railroad
gh Retirement Board, the Social Security Board, the Bureau of
E Internal Revenue of the Department of the Treasury, the De- ` _4
Q partment of Commerce, the Federal Trade Commission, and the »
i Tariff Commission. r V
¥ The following private agencies joined with the National z
  Research Project in conducting special studies: the Indus- l _
  trial Research Department ofthe University of Pennsylvania,
  the National Bureau of Economic Research, Inc., the Employ-
E ment Stabilization Research Institute of the Unlverslty of
§ Minnesota, and the Agricultural Economics Departments in the
i Agricultural Experiment Stations of California, Illinois, .
% Iowa, and New York.
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FEDERAL WORKS AGENCY  
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I e.c.HARRnNGroN i
COMMISSIONER OF WORK PROJECTS `  
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August 25, ww  
Colonel F. C. Harrington g
{ Commissioner of Work Projects yi
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__ Although bituminous coal has been declining in QI
importance as a source of fuel and energy, it is still ?.
this country•s principal energy producer and it still Qi
employs as many workers as all of the other mineral °,
industries combined. The average number of men em- 5
ployed reached an all—time peak of 7051000 in 1923. fl
From that point on employment declined almost steadily y 5
until 1932 when it was down to 406,000 men; since then ' i
· it has increased to 492,000 in 19§7. rig
1 The fact that coal mining was one of our sick T
industries even during the prosperous twenties is i
r attributable partly to the wartime inflation of ca- Q
pacity and partly to changes in demand. The high li
prices of the war led to the opening of new mines and Ҥ
further expansion of the capacity of an already over- 3
developed industry. At the same time oil, gas, and 3
hydroelectric power made inroads in the markets for J
coal and consumers turned to economies in the use of Ԥ
·‘ fuel. The former upward trend in coal demand flat- §
I. tened out. The combination of arrested demand and Q
' I surplus capacity produced an inevitable readjustment i
, and as early as 1924 the bituminous—coal industry i
' experienced acute depression. Q
Technical advances underground and on the surface é
reduced the number of men required to mine a given i
volume of coal, though doubtless aiding coal to meet é
_ the competition of other sources of power. At under- i
ground mines the average output per mine worker per g
‘ hour increased by 24 percent between 1920 and 1955. i
The continued spread of the mechanical devices that §
I were available before the war, such as the under- i
cutting machine; the electrification of underground lg
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p transportation; and improvements in mine lay-out and
i— management methods contributed toward the rising ,
Q . output per worker. Shortly after the war a new ma-
§»V chine, the mechanical coal loader, was introduced.
§ _ It is mainly with the progress of mechanical loading
§ i and its relationship to the other factors that in- V
fg, fluence production and employment in the industry that
éi this report is concerned.
i` In a mine in which coal is loaded by hand, from
ip, one-half to two-thirds of the entire working force
?;_ consists of miners who, in addition to undercutting
if the seam and preparing shot holes for blasting down
§·U coal, shovel the coal into mine cars. Most of their
gh time is spent in loading coal and the mechanization
¥~` of this process can obviously have an important effect
§§_ on the amount of labor required by the mines.
g.; Machine loading was adopted slowly in the early
Q" years of its introduction. Only 0.3 percent of all
underground bituminous-coal tonnage was loaded by ma-
{-, chine in 1923. By 1929 the percentage was 7.3 and in
°_ 1935 it was 13.5. Between 1935 and 1937 the machine-
9- loaded tonnage increased from 47 to 33 million tons,
Z] or to 20.3 percent of all underground production, and
, A it is estimated that in 1938 one-quarter of the output
I`. was loaded mechanically.
ir The installation of mechanical loaders has not
{ taken place at an even rate in all producing areas.
. , During the twenties and the years between 1930 and
V i 1935 it had its principal acceptance in the great
iv; Illinois—Indiana producing district and in some of the
L less important producing States of the far West. In
wl West Virginia, the country¤s leading coal producer,
JV 21 percent of the output was mechanically loaded in
f 1933 as compared with 2 percent in 1935. While it was
{ being adopted to an increased extent in other areas
C the coal loader also continued to be more extensively
f' used in Illinois and Indiana.
g It is estimated that within another decade as
{ much as half of the total underground output may be
{ mechanically loaded. How this will affect employment
Q in the industry depends upon a multitude of factors.
I Between 1929 and 1935 output per man—hour in under-
§ ground mines increased by 5 percent and production
?· declined by 32 percent, but the average number of men
·% employed declined by only 9 percent. The men have
5 worked fewer hours per day and fewer days per year.
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1 Technical progress has been a factor in aiding _?
J · coal to meet its competitors in the market and offers Q
— one means of maintaining adequate wage rates and work- §
- ing conditions. No student of the coal industry, E
J V however, foresees a revival of demand such as to en- Q
· able the industry to absorb any of the unemployed Q
t from other fields of labor. In fact, the most that 2
can well be hoped for is to maintain the working force rg
H now employed at the mines. i
9 If the cost of coal is reduced, new uses found, g
J and former markets recovered, mechanical loading will g
H result in the elimination of much of the backbreaking §
Y work of coal mining without exacting too great a price `3
¤ in terms of unemployment and reduced income. However, rf
t such a price has already been and is now being paid Q]
in some localities. Some mines and mining communities fw
which by virtue of natural conditions or other factors LJ
{ have been unable to adOpt mechanical loaders are being if?
placed in unfavorable competitive positions and are !
J finding their employment opportunities restricted. yi
_ Some of the older miners, accustomed to the tempo of `§
hand-loading mines, are finding themselves displaced E;
3 and unable to gain a foothold in the mechanized mines. lg
t To many of these communities and for many of these 'E
older miners emergency relief measures of one type d
or another are the only alternative to destitution #
{ as long, at least, as mass unemployment remains a Q
_ problem in the United States. 4
1 e
{ Respectfully yours, §
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S Corrington Gill §
S Assistant Commissioner §
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C O N T E N T S  
Chapter Page [Q
PREFACE ...................... xxiii {
I. INTRODUCTION ................... 1 E
II. MINING UNDERGROUND AND COAL PREPARATION, PAST IA`` i
AND PRESENT ................. B {
Machine cutting ................. 13 ‘@
Drilling and blasting .............. 20  
Underground haulage ............... 24 g
Mechanization of auxiliary services ....... 29 `Q
Mechanical loading ............... 31 ,€
r _1
Coal preparation .............. . . 31 ·`j
Screening ................... 32 fg
Cleaning ................... 33 yjf
Special treatments .............. 36 ‘ {
Growth of mechanical cleaning ......... 35 `M,
Interrelation of coal preparation and T
mining technology ............ 38 jg
Separation of mining and preparation ..... 40 3
Coal preparation and employment. . . . . . . . 41 xg
Technology in burning coal ........... 42 V_§
Equipment production .............. 44
III. RESOURCE CONDITIONS: THEIR INFLUENCE ON Q
MECHANIZATION AND PRODUCTIVITY ........ 47 i
Coal resources ................. 48 &
Coal areas . ................. 48 _Q
Topography .................. 49 Q
Cover ................... . . 49 Q
Structure ................... 50 rf
Rank . ..... . . . . . . ......... 50 é
Quality .................... 52 Q
Reserves ..... . . . . . . . . . . . . . . 53 E
Interrelation of resources, technology, §
and management. . . . . . . . . . . . . . . 54 §
Major resource factors ............. 57 {
Depth of cover ...... . . . . . . . . . . 58 E
Thickness of coal seam ............ 59 g
V Character of roof and overlying strata .... 62 E
Character of bottom or floor ......... 66 3
Character of the seam ............. 66 §
Dip or pitch of seam ............. 68 Q
Mine gases .................. 70 K
Mine water .................. 71 Q
Topography .................. 71 {
ciimate .................... *22 Q
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  _
g - Contingent factors ............... 72
é p Type of opening ................ 73 `
§ ~ Size of mine ................. 74
·§ Age of mine .................. 79
I ` Depletion of reserves ............. B0
i_` Management ................... B1
B` Man-day output — a resultant of numerous factors 64
i5` IV. STRIP MINING: A RESULT OF SPECIAL RESOURCE
? } CONDITIONS .................. B7
? Phases of strip-mining technology ........ 66
{_f' War stimulus to strip mining .......... 96 `
¥° Post-war progress ................ 97
;kn_ Competitive advantages of strip mining ..... 97 _
Q A Man—day output in strip mining ......... 101
*;i General characteristics of strip mining ..... 107
I Probable future significance of strip mining . . 108
L ~ V. HISTORY, DESCRIPTION, AND PRESENT DISTRIBUTION OF
"U MECHANICAL-LOADING DEVICES .......... 114
j Scrapers ............. . . ..... 116
" Pit—car loaders. . . . . . . .......... 119
I ‘ Duckbills (self-loading conveyors) . . . . . . . 123
CN Hand-loaded conveyors. . . . . ..... . . . ._ 125
V . Mobile loaders ................. 130
I Sales of loading equipment in 1936 ....... 139
fi, Intensive and extensive advance in
· mechanical loading ............. 140
j VI. INFLUENCE OF RESOURCE CONDITIONS ON MECHANICAL
I; I LoAD1Nc ................... 143
`M* Coal fields of the Mississippi Valley ...... 143
5 Illinois . . . . . . .... . . . . . . . . . 145
Q Indiana ........ . ...... . .... 150
é Western Kentucky . . ............. 154
¥ Michigan ................... 155
j` Iowa ..................... 155
I Kansas .................... 156
E Missouri ................... 156
Q Arkansas .......... . .... . . . . 156
j Oklahoma ................... 159
‘g Texas. . . . ......... . ....... 159
i Coal fields of the Rocky Mountains ....... 160
PE Wyoming .................... 160
f Montana .................... 161
g Utah ..................... 161
E5 Washington .................. 162
I Colorado ................... 162
{ New Mexico ............... . . . 162
;— North Dakota ................. 163
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‘ CONTENTS xi ._ 
Chapter Page g
Coal fields of the Appalachians .... . . . . . 163 i
` Pennsylvania . . . .............. 164 Ai
ohio ..................... iev §_
Maryland ........... . ....... 167 p Q
West Virginia. ................ 16B 1%
Virginia ....... . . . . . . . . . . . . 172 `Q
Eastern Kentucky ............... 173 Ag
Tennessee ................... 174 ‘·;
Alabama .................... 174 Q
VII. BASES FOR ANALYZINS PERFORMANCE OF MECHANICAL- AND 4%
HAND-LOADING MINES .............. 176 _3
i Nontecbnical causes of increased average Q
labor output ................ 176 #i
Concentration of production in more vii
{ efficient mines ............. 176 i·{
Shifts from old to new mining areas ...... 181 ij}
Changes in composition of the working force. . 165 fi?
Source and character of data . . . . . . .... 188 Q
Tonnage produced ............... 190 3
Number of men employed ............ 191 -'§
Share-the-work agreements ........... 194 `_
Time worked ............ . ..... 196 i g
Number of man—days .............. 195 ‘_i
Hours per day and total man-hours ....... 199 E
Summary .... . ...... . . ....... 201 p
Classification of mines ............. 203 g
Basis of classification ............ 203 N
Changes in the composition of groups ..... 206 4
Competition and regional distribution ...... 207 A q
Comparative significance of area data ...... 212 2
VIII. PERFORMANCE OF MECHANICAL- AND HAND-LOADING MINES “g
IN THE ILLINOIS-INDIANA AREA ......... 215 g
Illinois ............ . ....... 217 1;
Tons mechanically loaded ........... 217 i
Tons cut by machine .............. 220 T
Number of mines ................ 221 q
Production .................. 221 E
Hourly capacity. . . ..... . . .... . . 227 q
Men employed ........ . ........ 229 g
Share-the-work agreements and E
numbers employed ............ 230 g
Days operated per year ....... . .... 231 §
Tons per man-hour and number of men required §
to maintain 1,000 tons of hourly capacity 232 1
Comparative labor requirements with mobile i
loaders and pit-car loaders . . . . . . . 234 é
Indiana ..................... 2as  
Tons mechanically loaded ........... 239 §
Tons cut by machine .............. 242 V;
Number of mines ................ 242 'Q
Production .................. 243 €

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g Hourly capacity ........ . . . . .... 243
g Men employed ................. 244
§ Days operated per year ............ 244
é Tons per man-hour and number of men required
i to maintain 1,000 tons of hourly capacity 245
E. Comparative labor requirements with mobile
§u loaders and pit—car loaders . ...... 245
§ ` Composite employment factors in the Illinois-
é Indiana area. . . .......... . . . 247
2 v
g l IX. PERFORMANCE OF MECHANICAL- AND HAND-LOADING MINES
g 7 IN THE FAR WEST ............... 253
ij; Wyoming ........ . ............ 256
yl Tons mechanically loaded . . . . . ...... 257
{i1_ Tons cut by machine .............. 257
§"’ Number of mines ................ 257
} , Production .................. 258
_· I Hourly capacity. . .... . . . . . . .... 259
} Men employed ................. 259
I Days operated per year ............ 260
yy" Tons per man-hour and number of men required
Q N to maintain 1,000 tons of hourly capacity 260
{ j Montana ..................... 263
V" Tons mechanically loaded ........... 266
q Tons cut by machine .............. 266
I Number of mines ................ 267
V Production ....... . . . . ....... 267
Hourly capacity ............. . . . 268
" Q Men employed ................. 268
V Days operated per year ............ 269
~ ~ Tons per man-hour and number of men required
to maintain 1,000 tons of hourly capacity 269
1 A Washington ................... 270
Q; Tons mechanically loaded ........... 271
if, Tons cut by machine. . ............ 272
Q Number of mines ........... . .... 272
Q Production .................. 273
g Hourly capacity .... . ........... 273
· Men employed ......... . .... . . . 273
g. Trend of output per man ............ 274
f Prospects for the future ........... 275
{ Utah ...................... 276
{ Distortion of Utah figures due to practice
i of men working when tipple is idle .... 277
j Tons mechanically loaded ........... 277
i` Tons cut by machine .............. 280
I Number of mines ................ 280
g Production .................. 280
Q. Men employed ................. 281
5 Days operated per year ............ 281
{ Tons per man-hour and number of men required
? to maintain 1,000 tons of hourly capacity 281
P
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CONTENTS xiii  
Chapter Page €
Colorado . ......... . .... . .... 282 VE
Significance of far western experience .... . 283 g
3
X. PERFORMANCE OF MECHANICAL- AND HAND-LOADING MINES {
IN THE APPALACHIAN AREAS ........... 285 ,é
Central Pennsylvania . . . . .......... 286 E
Tons mechanically loaded ........... 286 _;
Tons cut by machine .............. 287 Q
Number of mines ................ 290 xg
Production ........... . . . . . . . 290 é
Hourly capacity ................ 291 {
Men employed ................. 291 ii lf,
Days operated per year ............ 291 f
Tons per man-hour and number of men required jx
to maintain 1,000 tons of hourly capacity 291 Qi
Western Pennsylvania and Ohio No. 8 field .... 294 `X
Tons mechanically loaded ...... . .... 294 LQA
Tons cut by machine .............. 295 »~J
Number of mines ................ 295 {
Production .................. 296 ri
Hourly capacity ................ 296 L
Men employed ................. 296 . g
Days operated per year ............ 297 ` Q
Tons per man-hour and number of men required .·g
to maintain 1,000 tons of hourly capacity 298
Ohio ...................... 298 j
West Virginia .................. 300 ;
Virginia . . . . ....... . . ....... 302 Q
Aiabama ..................... eos  
Tons mechanically loaded ........... 308 3
Tons cut by machine .... . . . . . ..... 306 g
Number of mines ................ 306 Q
Production .................. 307 g
Hourly capacity. . .... . ..... . . . . 308 §
Men employed ................. 308 3
Days operated per year ............ 308 g
Tons per man-hour and number of men required I
to maintain 1,000 tons of hourly capacity 309 §
XI. SUMMARY AND CONCLUSIONS .............. 312 Q
Performance of mechanical- and hand-loading §
mines in the United States, 1918-35 .... 312 §
Tons mechanically loaded ........... 313 g
Tons cut by machine .............. 313 Q
)‘
Number of mines ................ 313 j
Production .................. 316 Q
Hourly capacity ................ 317 E
Men employed ................. 317 Q
Days operated per year ............ 318 g
Tons per man—hour and number of men required j
to maintain 1,000 tons of hourly capacity 318 lg
Comparative labor requirements with different Q
loading devices ............. 320 §

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g A Nation-wide view of mechanization to 1933. . . . 324
E ` Outlook for the future ............. 333
-2 Pros ective advances in mechanical loadin . . 334
, P
§· Market factors ................ 336
E Mechanization and public policy ........ 339
gig Appendix
g` . F BASIC EMPLOYMENT DATA. . . 352
gbii Average number of men employed ......... 352
; _ Employees excluded .............. 352
§_y Absenteeism .................. 352
{ Monthly fluctuations in employment ...... 353
§T_ Share-the-work agreements ........... 354
élj Average number of days worked .......... 355
{ . B. TAatEs ...................... asv
g C. TRANSCRIPTION SHEET FOR U. S. BUREAU OF MINES DATA 433
E MAPS, CHARTS, AND ILLUSTRATIONS
‘ Figure
J
i‘ 1. Long-time trends of production, man-days, and labor
A. output ln the bituminous-coal industry, 1390-1936 5
j 2. Cutting machines .................. 16
3. Long-time trends in machine cutting of bituminous
I coal 1391-1936 .................. 13
l
4. Power drills .................... 21
' Q 5. Mine locomotives ............... _. . . 27
, 6. Modern bituminous-coal preparation plants ...... 35
· 7. Centers of mechanical coal cleaning in 1915, 1921,
P _ and ieee ..................... av
{ 3. Average depth of cover of underground bituminous-
E coal mines, by State, 1926 ............ 60
é 9. Percentage distribution of bituminous coal mined,
` by net seam thickness and State, 1920 ....... 64
I 10. Percentage distribution of bituminous coal mined,
{ by degree of dip of bed and State, 1920 ...... 69
Q 11. Percentage distribution of bituminous coal mined,
i by kind of opening and State, 1926 ........ 75
3 12. Airplane view of a strip mine ............ 33
`E 13. Early and modern strip shovels ........... 90
5 14. General view in strip mine . . . .......... 92
1 15. Net tons er man per day at all bituminous-coal
P
F mines, underground mines, and strip mines, 1910-36 102
{ 16. Output per man per day in major coal-stripping
E States, by kind of mine, 1910-36 ......... 104
i 17. Scraper loaders ................... 117
s y
I:  
§
 
 

   — _..:·‘  
comams xv  
MAPS, CHARTS, AND ILLUSTRATIONS—Continued ,§
Figure Page Q
a
19. Distribution of scrapers installed in underground E
bituminous-coal mines at the beginning of 1939 . . 119 {
19. Pit-car loaders .......... . ........ 121 yé
20. Distribution of pit—car loaders installed in E
underground bituminous-coal mines at the beginning ;§
of was ...................... 122  
21. Duckbill loaders .................. 124 é
22. Distribution of duckbill loaders installed in g
underground bituminous-coal mines at the beginning 15
of 1939 ...................... 125 é
23. Conveyors .............. . ....... 126 _Q
24. Distribution of hand-loaded conveyors installed in ii
underground bituminous-coal mines at the beginning ,bi
of 1939 ...................... 129 ¤·%
25. Shovel-type mobile loader .............. 131 Vwr
26. Tractor-mounted gathering-type mobile loader .... 132 _:
27a. Track-mounted gathering-type mobile loader ..... 134 Y
27b. Track-mounted gathering-type mobile loader .... . 135 `?§
29. Distribution of mobile loaders installed in _.€
underground bituminous-coal mines at the beginning ;
of 1939 ...................... 136 A
29. Underground bituminous-coal production mechanically K
loaded byall types of machines, by county, 1937. . 141 g
30. Percentage distribution of underground bituminous- `1
coal production mechanically loaded by all types · Q
of machines, by county, 1937 ........... 141 n
31. Illinois county distribution of tonnage mined by _?
stripping and underground tonnage loaded by mobile é
loaders, by pit—car loaders, and by hand, 1937 . . 149 3
32. Indiana county distribution of tonnage mined by E
stripping and underground tonnage loaded by mobile §
loaders, by pit—car loaders, and by hand, 1936 . . 153 j
33. Total underground production in western Kentucky é
and percentage mechanically loaded, 1919-36 .... 154 %
34. Pennsylvania county distribution of tonnage mined 3
by stripping and underground tonnage loaded §
mechanically and by hand, 1937 .......... 165 i
35. West Virginia county distribution of underground i
tonnage loaded by machines, by hand-loaded i
conveyors, and by hand, 1937 ........... 169 Q
36. Total underground production in eastern Kentucky E
and percentage mechanically loaded, 1919-36 .... 174 Q
37. Number of commercial bituminous-coal mines and %
percentage distribution of production, by size E
of mines, 1905-36 ................. 179 }£
 
$5
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g
  xvi CONTENTS
Q
i .
Q MAPS, CHARTS, AND ILLUSTRATIONS-Continued
Q Figure Page
g 39. Indexes of output per man-day and per man-hour
§ in the bituminous-coal industry, 1903-39 ..... 190
Q 39. Comparative performance in Illinois of underground
Q _ mines which have adopted mechanical loading and
F` of all other underground mines, 1919-35 ...... 219
{ , 40. Tonnage mechanically loaded and unit labor
§ ` requirements at Group A mines in Illinois, by
{ ' type of loading equipment used, 1919-35. . . . . . 236
E 41. Average increase (or decrease) in tons per man-hour
i in a mechanical-loading period, 1931-35, over a
ig hand-loading period, 1919-22, for 43 Illinois
Q Group A mines, bytype of loading equipment used. 237
} » 42. Comparative performance in Indiana of underground
1 mines which have adopted mechanical loading and
&. of all other underground mines, 1919-35 ...... 240
` 43. Tonnage mechanically loaded and unit labor
j requirements at Group A mines in Indiana, by
, type of loading equipment used, 1919-35 ...... 249
g` 44. Indexes of production, man-hours, and unit labor
2 . requirements at Group A and all other mines in
the Illinois-Indiana Area, 1919-35 . .... . . . 249
it 45. Comparative performance in Wyoming of underground
‘ mines which have adopted mechanical loading and
of all other underground mines, 1919-35 ...... 254
49. Comparative performance in Montana of underground
§ mines which have adopted mechanical loading and
I of all other underground mines, 1919-35 ...... 264
47. Comparative performance in Washington of underground
mines which have adopted mechanical loading and of
` all other underground mines, 1919-35 ....... 271
Q 49. Comparative performance in Utah of underground mines
g which have adopted mechanical loading and of all
§ other underground mines, 1919-35 ......... 279
§ 49. Total underground production in Colorado and
{ percentage of output mechanically loaded, 1919-37 293
{ 50. Comparative performance in central Pennsylvania of
{ underground mines which have adopted mechanical
i loading and of all other underground mines,
Q 1919-35 ...................... 299
¤
j 51. Comparative performance in western Pennsylvania and
j in the 0hio No. 9 field of underground mines which
2 have adopted mechanical loading and of all other
g` underground mines, 1919-35 ............ 292
¥ 52. Total underground production in Ohio and percentage
i of output mechanically loaded, 1919-37 ...... 299
L 53. Total underground roduction in West Vir inia and
{ V P
{ percentage of output mechanically loaded, 1919-37 301
it
 
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E
i

 JKT ¤ {
£’§4 F E
ii
CONTENTS xvii  
MAPS, CHARTS, AND ILLUSTRATIONS—Ccntinued ,§
Figure Page E
54. Total underground production in Virginia and ?
percentage of output mechanically loaded, 1918-37 302 E
X.
55. Comparative performance in Alabama of underground ,Q
mines which have adopted mechanical loading and 4}
of all other underground mines, 1918-35 ...... 304 Q
56. Comparative performance in the United States of ii
underground mines which have adopted mechanical E
loading and of all other underground mines, *
1918-35 ...................... 314 %
57. Distribution of hand-loaded, mechanically loaded, T
and strip-mined bituminous coal, by State, 1930 A
and 1935-37 .................... 323 `»j
58. Distribution of mechanically loaded bituminous coal, ii
by type of loader and State, 1930 and 1936 .... 331 ,ff
B-1. Output per man per day in selected States, ,:i
by kind of mine, 1910-36 ............. 432 i
TEXT TABLES g
Table . §
1. Occupations in a hand-loading and a mechanical- g
loading mine ................... 12 E
2. Coal produced in underground bituminous mines in l
working places where shot holes were power-drilled Q
and percentage of total underground output power- _?
drilled, cut by machines, and mechanically loaded, fi
1936 ....................... 22 · i
3. Production of mechanically cleaned bituminous coal, 3
by use, 1927-36 .................. 39 g
4. Average British Thermal Units per pound of coal ,
produced, by division and State, 1936 ....... 53 i
5. Percentage distribution of coal reserves and coal §
production, by division and State, 1936 ...... 55 Q
1
6. Distribution of number and production of commercial i
bituminous-coal mines, by size and State, 1936 . . 76 3
7. Labor requirements of a large strip mine with 1
an average daily production of 6,000 tons ..... 94 §
8. Summary of bituminous strippi