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poses underground, a large number of mules are still employed, but the deaths caused by the kicks of these animals, or otherwise in connection with the handling, driving, etc., of the same, number only 73, or 0.4 per cent. The two remaining specific causes are asphyxiation and electrocution. The former caused 271 deaths, or 1.5 per cent of the total, and the latter 193, or 1 per cent. Both of these are important causes, which for their full understanding require to be considered in detail, as disclosed by a careful consideration of a suficient number of individual cases.

PRINCIPAL CAUSES OF FATAL ACCIDENTS BY COAL FIELDS. The relative proportion of principal causes naturally varies widely, according to the geological character of the coal fields, the method of mining, the presence of dust or dangerous gases, the use of coal-cutting machinery, compressed air and electricity, etc. In the table which follows a comparison is made of the distribution of principal causes in the different coal fields, amplified in the appendix by tables for the several coal-mining States. It would carry the present analysis too far to discuss the variations in causes, as determined by the percentage basis in detail, since they will be further considered on the basis of the exposed to risk of death one year for the several States. (See Table XXIII of the appendix.)

PER CENT OF FATAL ACCIDENTS IN THE COAL MINES OF NORTIL AMERICA

DUE TO EACH CAUSE DURING A TEN-YEAR PERIOD, BY GEOGRAPHICAL SECTIONS.

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Falling of coal.
Falling of roof, slate, etc.
Falling into shafts.
Falling into slopes, manways, etc.
Mine cars.
Outside cars..
Motors.
Explosions:

Dust or gas.
Dynamite or powder.
Blast....

Other, not specified.
Mining machinery
Mules..
Asphyxiation.
Electrocution
Miscellancous.

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11.2
2.6
4.3

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2.4

.5 1.9 1.2

.2

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6.1

33. 2
5. 3
.8
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1.0
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1.4
3.6

14.0 5. 3 4.3 1.6 1.8

1.2

.3 1.0

8.9 20.5 3.3 .3 .5 .2 1.9

.8

1.5 1.0 6.0

.6 6.3

.5 7.8

.9 1.7

.7 10.5

8. 2

SUMMARY.

49.4
3.0

42.0
5.3

45.8
3.9

44.5
3.2

41.7
1.0

49.0
1.3

27.7
1.7

46.6
2.7

Falling of coal, rooi, etc..
Falling into openings..
Mine cars, railroad, and other trans-

portation agencies.. Explosions.

All causes.

16.9
18. 3

22.9
15.5

14. 3
25. 2

8.5 33.7

11.4 39.5

11.5
33.0

10.9
47.1

14.8 25. 2

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

The table is self-explanatory and requires no extended analysis. It is shown, for illustration, that in the eastern section (Maryland, Ohio, and Pennsylvania) falls of coal caused 10.6 per cent and falls of roof, rock, slate, etc., 38.8 per cent, a total of 49.4 per cent, against 21.2 per cent of deaths from fall of coal and 20.8 per cent of deaths from fall of roof, slate, etc., in the northeastern section (Nova Scotia). The highest percentage proportion of deaths caused by fall of coal occurred in the east central section, or 36.9 per cent, while the lowest occurred in the Pacific coast section, or 9.4 per cent. The highest percentage of deaths caused by falls of roof, slate, etc., occurred in the eastern section (Maryland, Ohio, and Pennsylvania), or 38.8 per cent, while the lowest occurred in the east central section, or 8.9 per cent. Unquestionably, some of these differences are the result of variations in the method of reporting the causes, but the differences are too pronounced to be solely due to this possible source of error. When combined the results, in order of relative importance, are as follows:

PER CENT OF DEATUS FROM FILLS OF COIL AND OF ROOF, SLATE, ROCK,

ETC., IN COAL MIXES OF NORTII AMERICA, BY GEOGRAPHICAL SECTIONS.

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There is evidently no very definite or even approximately welldefined relation between the degree of frequency of occurrence of these two closely allied and often identical causes. The most marked opposite conditions are shown to have prevailed in two coal fields not greatly different in geological characteristics or general mining methods; that is, the eastern (Maryland, Ohio, and Pennsylvania) and the east central section (Illinois and Indiana). In the former, fall of coal caused 10.6 per cent, against 36.9 per cent in the latter, so that the combined totals of 49.4 and 15.8 per cent do not vary materially. It may therefore be assumed as a reasonable probability that the two causes are often inclusive of each other, and that for statistical purposes they should be considered as a group, more or less similar in the underlying causes, conditions, and methods of mining responsible for their occurrence.

The summary table (p. 459) brings out the local significance of other causes, which in some cases eren exceed in importance the fatality rate from fall of coal, roof, etc. Explosions due to gas or dust or the use, storage, etc., of explosives caused the largest proportionate mortality on the Pacific coast section, or 47.1 per cent. Arranged in the order of importance, the fatality percentage due to this group of causes was 39.5 per cent in the southern coal fields, 33.7 per cent in the west central section, 33 per cent in the western section, 25.2 per cent in the east central section, 18.3 per cent in the eastern section, and only 15.5 per cent in the northeastern section. The extremes in the casual occurrence of fatalities due to explosions, as would naturally be expected, were therefore of a wider range, or from 47.1 per cent to 15.5 per cent, against a range of from 49.4 per cent to 27.7 per cent for fatalities caused by falling of coal, roof, etc.

“Falling into openings” considered as a group caused 2.7 per cent of all the fatal accidents in the whole coal area, but the proportion varied between only 1 per cent in the southern section to 5.3 per cent in the northeastern. The differences are chiefly due to the

. fact that there are few deep mines or vertical mine openings in the southern coal fields, where most of the coal is mined by horizontal slopes, tunnels, etc., while in the central coal fields of Pennsylvania, for illustration, practically all the mining is by shaft. The liability to death on account of falling into openings is therefore largely governed by the methods of mining, which vary widely, according to the nature of the coal beds of the several States.

Fatal accidents caused by mine cars, railroad, and other trans; portation or hauling agencies varied from an average of 14.8 per cent for the North American coal fields as a whole to 22.9 per cent for the northeastern coal fields and 8.5 per cent for the west central section. These proportions are also governed largely by local conditions, mining methods, etc., which require to be determined by special inquiry and a thorough analysis of a large number of individual cases. The summary table gives the available information in detail, but, as previously explained, the facts must be considered with great caution and always with a due regard to the geological characteristics of the different coal fields and local variations in methods of mining, labor supply, use of coal-cutting machinery, electricity, etc.

A further consideration of the causes of fatal accidents in coal mining is made possible, at least for some of the States for which the facts are made public in more detail. As far as practicable, in the tables for the several States, all the essential facts contained in the annual reports of the state mine inspectors have been considered, which explains why for some States much more detailed returns are available than for others. The practical value of this analysis will be better understood when it is stated that heretofore the Uniteil States Geological Survey has given the details of causes of fatal accidents in only 3 specific groups, while in some of the tables in the appendix to this study the facts are given in detail in 21 groups The practical value of the tabular analysis of coal-mining accidents, provided the facts by causes are sufficiently numerous, is, of course, in exact proportion to the detailed grouping of individual but welldefined specific causes responsible for coal-mining casualties. Much would be gained by uniformity in the method of tabulation by causes, but efforts in this direction should insist rather upon a comprehensive tabular analysis than upon condensation. (a)

The importance of details is best illustrated by specific causes of modern significance, such as deaths due to mining machinery, electricity, boiler explosions, etc. (For further details of the causes of accidents by States, see Table XXIII of the appendix.)

THE FATAL-ACCIDENT RATE DUE TO PRINCIPAL CAUSES.

The rate of fatal accidents by principal causes determines with scientific accuracy the degree of risk exposure to particular hazard in mining experience. The following table is identical with the table on page 454, previously discussed, except that for each cause the rate per 10,000 exposed to risk has been calculated, instead of the percentage distribution of causes, as in the former table. Since the number of some of the causes is small, it has seemed best to use 10,000 employees exposed to risk one year, instead of the usual basis of 1,000. The table is based upon a risk exposure of 5,459,436 mine workers for one year and 18,346 fatal accidents occurring in the coal fields of North America during the decade ending with 1908, or a part thereof, since the returns for some of the States are not complete. The rates for individual coal-mining States and the details for the different coal areas, by number of casualties and the rate per 10,000, will be found in Table XXIII of the appendis.

a For suggestions for improving coal-mining accident statistics, see Engineering and Mining Journal, June 2, 1900, and subsequent issues. Among the more important works on the causes of coal mining accidents are vining Accidents and their Prevention, by Sir Frederick Augustus Abel, New York, 1859: Explo. sions in Coal Mines, by W. N. and J. B. Atkinson, London, 1886; Essays on the Preventiou of Explosions and Accidents in Coal Mines, by Creswick, Galloway, and Hopton, London, 1574; Elements of Mining and Quarrying, by C. Le Neve Foster, London, 1903; and Practical Coal Mining, by T. II. Cockin, New York,

FATAL-ACCIDENT RATE IN THE COAL MINES OF NORTH AMERICA DURING A TEN-YEAR PERIOD, BY CAUSES.

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Asphyxiation.
Electrocution..
Miscellaneous..

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.13

.50

.35 2.02

Total.

Western..
Southern..

Pacific coast..

Standard or average rate.

Eastern....

East central.

West central..
Northeastern.

Section.

1,105

18,346

The average fatality rate for the North American coal field, according to this table, was 33.6 per 10,000, or 3.36 per 1,000 of persons employed one year.

FALLS OF COAL OR ROOF.

The average fatality rates by principal causes during the ten-year period 1899 to 1908, as given in the above table, may be considered the standard by which the relative frequency of accident occurrence in the different coal fields and coal-mining States can be measured. The standard rate of accident occurrence due to fall of coal and roof, slate, etc., combined was 15.67 per 10,000, but, as brought out by the following comparison, the degree of risk varies considerably in the different coal fields.

33.60

FATAL-ACCIDENT RATES IN COAL MINING DUE TO FALLS OF COAL, ROOF, SLATE, ETC., DURING A TEN-YEAR PERIOD.

Rate per 10,000 employees.

34.08

21.57 21.13

15.67

15.33

11.€8 11.06

10.44

This comparison is of very considerable practical significance. For the first time, the true rate of risk from a particular cause in mining

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