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be better understood when it is stated that heretofore the United 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. (")

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 appendix.

"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 Mining Accidents and their Prevention, by Sir Frederick Augustus Abel, New York, 1889: Explosions in Coal Mines, by W. N. and J. B. Atkinson, London, 1886; Essays on the Prevention of Explosions and Accidents in Coal Mines, by Creswick, Galloway, and Hopton, London, 1874; Elements of Mining and Quarrying, by C. Le Neve Foster, London, 1903; and Practical Coal Mining, by T. H. Cockin, New York,

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

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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.

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

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

operations is here precisely determined by a method which has the sanction of statistical science, and the result is startling, indeed.

The table brings out the fact that in some of the coal fields the fatality rate due to a single group of related causes; that is, fall of coal and roof, slate, etc., is as high, or higher, than the normal fatality rate due to all causes in most of the coal-mining States and Provinces of North America. Even the standard rate, of 15.67 per 10,000, or 1.57 per 1,000, is extremely high, higher, in fact, than the normal fatality rate due to all causes in the United Kingdom, Austria, and Belgium. In the far western coal area the rate has been 34.08 per 10,000, or higher than the fatality rate due to all causes for the whole American coal field. The southern, Pacific coast, and western coal areas all have decidedly higher average rates for this group of causes than the North American coal fields as a whole, while the northeastern, the east central, west central, and eastern sections experienced fatality rates due to fall of coal and roof below the standard, but in the last-named area the rate was very close to the average, so that with the exception of the northeastern and the central sections the fatality rate due to fall of coal and roof, slate, etc., must be considered high, and in some cases extremely high for the entire coal field of North America.

The variations in fatality rates due to fall of coal and roof for the different coal-mining States are, of course, much greater, but they can not be fully discussed here. By reference to Table XXIII of the appendix the facts for each State are made available in the most convenient manner, but the extremely high rates for some of the States may be briefly referred to. In Colorado the rate reached 35.15 per 10,000 out of a total rate, from all causes of accidents, of 55.99, or 62.8 per cent. In New Mexico the fatality rate due to fall of coal and roof was still higher, attaining to 40.48 per 10,000 out of a total rate for all causes of 72.69, or 55.7 per cent. In Utah more favorable conditions prevailed, but the rate reached 21.56 per 10.000 out of a total of 133.25, or 16.2 per cent. These rates admirably illustrate the danger of reasoning exclusively from a percentage distribution of causes; for, while the fatality rate due to fall of coal and roof in Utah is considerably above the standard (15.67), it is only 16.2 per cent of the deaths from all causes, and thus apparently lower. This apparent contradiction is due to the fact that a very disastrous explosion occurred in Utah in 1900, which increased the proportion of deaths due to this cause to 73.5 per cent of the whole number. It is evident that for an accurate understanding of the causes of coal-mining casualties, the rate of accidents by cause is required in place of the percentage distribution, but it is equally true that for many practical reasons, particularly such as govern in considerations of pre

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SHAFT ACCIDENTS

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The standard fatality rate for the oral 54ls of North America from shift ardents or falls into shafts manwaps, slepes, etc., was 091 per 100000 employed. This cause is, therefore, apparently not of great numerical significance, as only 404 deaths were caused in this manner, although it is safe to assume that a considerable number of these accidents were preventable. The variations in rates in the different cal field is shown in the following table:

FATALUNYA TIENT RATES IN COAL MINING IN NORTH AMERICA DUE TO SHAFT ACCIDENTS, FOR THE PERIOD 1899 TO 1908,

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The range in rates is from 0.53 in the southern coal field by A per 10,000 in the northeastern coal area. Of couper, the doublaky Ang falls into shafts, as has previously been said, is in proporkom by Ma number of employees in mines with vertical shaft entranc proportion of such accidents is naturally lowest mood held seams above sea level entered by tunnels, drifts, or dope "Shaft accidents," it should be explained, is not one of park, A ing in some of the mine inspectors' reports, and it is not cloak whiridan a deaths due to objects falling into shafts have alway. bon mncluded (as they should have been) or whether they base been grouped under miscellaneous. The importance of the sugge Con is made clear by reference to Table XXIII of the appendix which the detail 2

given for the State of Illinois. In that table it is shown that there were 46 deaths due to employees falling in to shafte, og ivalent to a rate of 0.87 per 10.000; 53 deaths due to object, falling into shafts, equivalent to a rate of 1 per 10,000; 13 death. due to falling of other miscellaneous objects, or 0.25 per 10,000; and finally, 47 death, due to cage accidents, or 0.59 per 10.000, When the four group are combined, it is brought out that shaft ace.dent. proper cau cd 169 fatalities, or nearly as many as mine cars, which can cd 160 deaths. Calculated upon the basis of every 10,000 po on employed, the fatality rate for Illinois due to all shaft accident- was 2.91 pu 10,669. 62717-No. 96 10 - 3

which contrasts with an average for the coal fields of North America of 0.91. But the excessive shaft accident rate for Illinois is by no means an exception. In Indiana the combined rate was 2.87, for Oklahoma 3.11, for Iowa 2.18, for Nova Scotia 2.64, and for Washington 3.99 per 10,000. Accidents of this kind constitute, therefore, quite an important factor in the fatality rates of certain States, and it may be assumed that if the returns were everywhere accurate and complete the true fatality rates due to shaft and cage accidents of all kinds would be higher than the rates as officially returned and given in the above table and in Table XXIII of the appendix. (a)

MINE CARS.

Mine cars caused 2.204 fatal accidents in the North American coal fields during the decade ending with 1908, out of a total of 18,346 accidents from all causes. The standard or average fatality rate due to mine cars was 4.04 per 10,000 employees, but the rates vary considerably in the different coal areas, as shown by the following table:

FATAL-ACCIDENT RATES IN COAL MINING IN NORTH AMERICA DUE TO MINE CARS, FOR THE PERIOD 1899 TO 1908.

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The mine car fatality rate ranges from a minimum of 2.05 per 10,000 for the west-central section to 8.01 per 10,000 for the Pacific coast section. Mine equipment, of course, has a bearing upon the degree of accident occurrence, but how far this is the case can not be determined by the brief account rendered in most of the official reports on accidents of this class. Riding on loaded cars contrary to orders is probably one of the chief reasons for the difference, and another probable reason is in the better discipline and control of mine labor in the Eastern States compared with the South and West.

Among the States and Provinces, with rates of mine car fatalities. much above the average, reference may be made to British Columbia with a rate of 7.63; Colorado, 7.01; Oklahoma, 7.26; Utah, 8.33; Washington, 8.37; and West Virginia, 6.18 per 10,000.

See also the Report of the Committee appointed by the Royal Commission on Mines to Inquire into the Causes of and Means of Preventing Accidents from Falls of Ground, Underground Haulage and in Shafts; Parliamentary paper Cd. 4821, London, 1909.

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