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ventive measures, the percentage distribution, as emphasizing the actually most important cause, is very useful; in fact, quite indispensable.

SHAFT ACCIDENTS.

The standard fatality rate for the coal fields of North America from shaft accidents or falls into shafts, manways, slopes, etc., was 0.91 per 10,000 employed. This cause is, therefore, apparently net of great numerical significance, as only 494 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 coal fields is shown in the following table:

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FATAL-ACCIDENT 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 fields to 1.32 per 10,000 in the northeastern coal area. Of course, the liability to falls into shafts, as has previously been said, is in proportion to the number of employees in mines with vertical shaft entrance, and the proportion of such accidents is naturally lowest in coal fields with flat seams above sea level entered by tunnels, drifts, or slopes. The term “shaft accidents," it should be explained, is not one of precise meaning in some of the mine inspectors' reports, and it is not clear whether deaths due to objects falling into shafts have always been included (as they should have been) or whether they have been grouped under miscellaneous. The importance of this suggestion is made clear by reference to Table XXIII of the appendix, in which the details are given for the State of Illinois. In that table it is shown that there were 46 deaths due to employees falling into shafts, equivalent to a rate of 0.87 per 10.000; 53 deaths due to objects falling into shafts, equivalent to a rate of 1 per 10,000; 13 deaths due to falling of other miscellaneous objects, or 0.25 per 10,000; and, finally, 47 deaths due to cage accidents, or 0.89 per 10,000.

When these four groups are combined, it is brought out that shaft accidents proper caused 159 fatalities, or nearly as many as mine cars, which caused 175 deaths. Calculated upon the basis of every 10,000 persons employed, the fatality rate for Illinois due to all shaft accidents was 3.01 per 10,000,

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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 2.61, 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 2.201 fatal accidents in the North American coal fields during the decade ending with 1908, out of a total of 18,3310 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 COIL MINING IN NORTH AMERICA DI'E TO MIXE

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.

a 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, I'nderground Haulage and in Shafts; Parliamentary paper (d. 4921, London, 1909.

OUTSIDE CARS.

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Outside car accidents caused 470 deaths in coal-mining operations in North America during the period under consideration, or 2.6 per cent of the fatalities due to all causes. In proportion to the number employed the standard or average fatality rate due to this cause was 0.86 per 10,000. Since practically all of these accidents occur to outside employees they should perhaps have been calculated with reference to outside employments only, but the necessary information as to the number of outside employees is not available for the North American coal fields as a whole. The statistics for Pennsylvania prove conclusively that most of the fatalities due to outside cars have occurred to outside employees. As brought out in the subsequent discussion of the fatal accident rate by occupations, the rate of outside car accidents to underground employees in Pennsylvania was 6.3 per 10,000 for the anthracite coal field and 3.9 per 10,000 for the bituminous coal field. In the anthracite coal fields 38.2 per cent of outside accidents were due to outside cars, and in the bituminous coal field 45.9 per cent.

The term “outside cars," as used in mining statistics, is, however, of a rather indefinite meaning, at least for some of the coal areas, and there are strong reasons to believe that in some of the States this class of accidents is combined with "mine car” accidents, which have been previously discussed. Most of the outside car accidents in the consolidated table have been reported from Pennsylvania and the eastcentral section, and it is, therefore, very doubtful whether the rates for other coal fields and coal-mining States can be accepted as accurate. For some of the States no outside accidents at all have been separately returned, although it is a practical certainty that such accidents have occurred. For this reason a discussion of the fatality rates by States would obviously be of no practical value. It may be emphasized here, however, that the risk factor due to outside cars is, undoubtedly, one which demands serious consideration.

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MOTORS.

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Motors caused a total of 30 fatal accidents in the coal fields of North America during the period under consideration, or 0.2 per cent of the casualties due to all causes. The standard or average fatality rate due to motors was 0.05 per 10,000 employed, the rate having been highest in the western section, where it reached 0.14 per 10,000, and zero in the west central section, for which no fatalities of this kind were officially reported. It is very doubtful whether all the fatal accidents due to motors used in mines have been properly classified as such, and it may reasonably be supposed, considering the rapid increase in the use of electric motor power in mining, that more deaths have occurred than have been officially reported, or properly classified. Granting probable defects in the returns, it is surprising to find that the fatality rate due to motors should be as low as 0.06 per 10,000 in the eastern coal field, which comprehends the States of Maryland, Pennsylvania, and Ohio. In Illinois, for illustration, out of 1,391 fatal accidents only 4, or 0.08 per 10,000 employed, were officially ascribed to motors, while in Ohio 19 out of 1,0:27, or 0.17 per 10,000 employed, were attributed to this cause. No deaths due to motors were officially reported as having occurred in the coal mines of Pennsylvania, which, no doubt, is partly due to errors in classification. For these reasons, it would serve no practical purpose to discuss the fatality rates due to motors in the different coal areas and coal mining States, but the self-evident defect in coal mining statistics clearly brings out the necessity of a uniform classification of causes to be agreed upon by the mining officials of the different States.

EXPLOSIONS OF GAS OR DUST. Statistical defects are inherent in all classification, but they can be materially reduced by a critical examination of individual returns. Of no group of causes is this more true than of gas and dust explosions, explosions of dynamite and powder, blasts, etc. There are practical difficulties to be overcome which at times will baffle even the most skilled, for cause and effect will often be confused, and it will occasionally occur that the true but insignificant cause of a coalmining accident is overshadowed by the disastrous effect. A can of powder explodes and results in a subsequent gas and dust esplosion with a considerable loss of life. Should such an explosion be classified under explosives or explosions? Or, a naked light ignites fire damp and causes a small gas explosion, which results in the explosion of an underground powder magazine, with disastrous results to life. Should such an accident be classified as gas explosion, or as a powder explosion? A compromise is necessary in such cases, but it would be of great value if definite rules governed in the statistical classification. It is due to these differences in the determination of the true cause that so many apparent errors and contradictions occur in coal-mining accident statistics and without a definite understanding among the different mine officials, a decided improvement can not be expected for many years to come.

As classified in Table XXIII of the appendix, there have been 2.571 fatal accidents due to gas and dust explosions in the coal fields of North America during the period under consideration, or 14 per cent of the fatalities due to all causes. The standard or average rate of accident frequency was 4.71 per 10,000, against 4.04 for mine cars and 1.77 for deaths due to explosions of powder or dynamite. Gas and dust explosions, therefore, are among the most important causes of mining

fatalities and their geographical distribution is a matter of particular importance.

The rariations in rates in the different coal fields are shown in the following table:

FATAL-ACCIDENT RATES IN COAL MINING IN NORTH AMERICA DUE TO GAS

OR DUST EXPLOSION, FOR THE PERIOD 1899 TO 1908.

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The rariation in rates ranges from a minimum of 1.25 per 10,000 for the east-central section to 17.17 for the southern section. The wide range is due primarily and largely to fundamental differences in the character and depth of the coal beds in the several coal areas, which are brought out in a striking manner by reference to the tables for the different coal-mining States. Gas and dust explosions have been combined, because of the fact that dust explosions per se are probably extremely rare in coal mines, while dust explosions caused by previous gas explosions are quite common, and particularly so in some of the States of the southern and Pacifie coast fields. Coal dust, as a factor in mine explosions, has only been regarded as such within very recent years, after a number of particularly serious disasters, in which there could be no doubt that what had been a gas explosion in its inception had subsequently become an explosion of coal du-t. There is probably no more serious question to-day in many of our mining States than the increasing danger of dust explosions, due possibly to the use of coal-mining machinery and to other causes which, as yet, are not fully understood. The subject of du-t explosion is too complex to be discussed in this place, (a) but it may be pointed out that measures of prevention in

a The most important recent contribution to the subject is Bulletin 425 of the United States Geological Survey, on “The Explosibility of Coal-dust," Washington, D. ('., 1910. This bulletin includes a very complete bibliography. Reference should also be had to Bulletin 383 of the United States Geological Survey, on “ Notes on Explosive Mine Gases and Dust," by R. T. (hamberlin, 1909. Among other important recent contributions reference should be had to an article on “ The Dust Problem in Coal Mines," by Joseph Virgin, Engineering and Mining Journal, October 9, 1909; “ Coal-dust as a Factor in Mine Explosions," by Henry M. Penn, Engineering and Mining Journal, July 4, 1908; “ Equipment for the Prevention of Mine Explosions, with Special Reference to

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