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to the time of employment, but the amount of idleness would have to be quite considerable to materially impair the accuracy of the fatality rate as determined by the usual method. In the above comparison there is a difference of 36 days, and if this is allowed for by reducing the two years to a common basis of 300 working days, the resulting rates are 5.96 and 5.46 per 1,000. The actual difference in the rates for 1907 and 1908, as determined by the usual method, is 1.26 per 1,000, or 35 per cent, while the corrected fatality rates show a difference of only 0.50 per 1,000, or 9.2 per cent. This difference corresponds quite closely to the result obtained by comparing the fatalities per million tons of coal mined. While, apparently, the corrected rates are more trustworthy than the rates determined by the usual method, it must be taken into consideration that the employment statistics have, in all probability, a very considerable degree of inaccuracy, on account of the fact that there are no uniform rules for determining the number of days worked in the different States and at different times. In view of this element of uncertainty and the limited extent to which information is available for correcting the fatality rates for variations in working time, as well as the very great amount of work involved in any attempt to make such corrections, it seems necessary at the present time to confine comparisons of coal mining fatalities to rates calculated according to the usual methods. The effect of variations in working time would be more pronounced in the case of nonfatal accidents, which, however, for reasons previously stated, have not been considered in this investigation.
Finally, there is the element of uncertainty in the returns of working time of miners working by contract and local variations in the permissible working time per day, which in the anthracite region of Pennsylvania is limited to nine hours. In the bituminous region of Pennsylvania during 1907 and 1908, according to the statistics of the United States Geological Survey, the working time was distributed as shown in the following table:
NUMBER AND PER CENT OF MEN WORKING SPECIFIED HOU'RS PER DAY IN
BITUMINOUS COAL MINES, 1907 AND 1908.
(Compiled from Mineral Resources of the t'nited States, 1908, Pt. II, p. 43.)
Men working specified hours per day.
Hours per day.
55, 278 125. 998 19, 489
61. 1 10.7 24.4 3.8
The differences in working hours from year to year are also hardly sufficient to have a really important bearing upon the degree of fatal accident occurrence, although it would be desirable, of course, to have a full statement of the actual hours of work, so that an exact comparison could be made of the true risk exposure as measured by time. Moreover, it is not to be questioned that as a general principle of human mortality and the nature of physical and mental fatigue that the shorter the hours of work in laborious employments the less will be the true accident liability, fatal or otherwise.
Possibly more serious are the actual errors which underlie the compilation of the average number of men employed. It is impossible to state by what method some of these so-called official averages are arrived at. In some cases it is quite possible that the number of employees on a given date has been taken as the average for the year; in others it would seem that the different names on the pay roll have been assumed to represent the “average
average” number employed, selfevident as this error obviously is. The correct “average," of course, is to add the number of persons employed each day and divide by the number of days the mines have actually been in operation, and hardly any other n.ethod would seem satisfactory as a substitute, although the addition of the number employed at the beginning or end of each month, divided by the number of months for which the returns are made, will give an average sufficiently accurate for all ordinary statistical purposes. In this case, also, the fact must not be overlooked that the number of fatal accidents in coal mining is rarely as much as 5 per 1,000 of men employed per annum, so that an error in the average number employed is of much less statistical significance than an error of even a few deaths in the number officially reported as having been killed in mining during the year. To illustrate, if the average number of men employed in 1908 had been returned as 650,000 instead of 690,000, a difference of 40,000 in number and of 5.8 in per cent, the rate per 1,000 would only have been changed from 3.60 to 3.77. Errors of this kind have a tendency to balance themselves in the course of years, but a willful omission of deaths or deliberate overstatements of the number employed, it is needless to say, can not be too seriously condemned.
Occasionally a labor trouble of state or nation wide magnitude seriously disturbs the normal conditions of mine work, so much so as to impair materially general calculations of fatal accident frequency upon the basis of the average number exposed to risk one year. The effect of such strikes is sometimes less in the case of the actual days' labor lost than in the average number of days lost per man, as illustrated by the experience of 1902, when 200,452 men went out on strike, losing 16,672,217 days' labor, or an average of 83 days per man, against 372,343 men who went on strike in 1906 with a loss
of 19,201,348 days of labor, or an average of 51.5 days per man.() In 1907 the loss was 14 days and in 1908 it was 38 days per man on strike in bituminous mines, but, of course, to determine the true effect of labor disturbance on the whole mining population would require different methods of statistical calculation than are in general use in the United States or Canada. For the present purpose it has, therefore, not been feasible to take the effect of strikes upon the risk exposure into consideration in the calculation of the fatality rates which are to follow.
There exists, no doubt, a fairly well-defined relation between the average coal production per man per day and the relative degree of risk to fatal accident occurrence. The probability of some such relation has been insisted upon by foreign writers on fatal accidents in American mines, and not without some conclusive evidence that the pressure and driving force back of the American miner is, in part, responsible for at least a fair proportion of the fatal accidents in our mines. The statistics of the United States Geological Survey show that the average production per man in 1908 varied from 340.8 tons per annum for Oklahoma (or 1.98 tons per day) to 793.9 for Wyoming (or 3.66 tons per day).(%) That there is not, however, an exact relation between the average annual production and the average daily production is made clear by the returns for some of the States, as, for illustration, for West Virginia, which has the highest average daily tonnage (and, it may be said here, also the highest average fatal accident rate in 1908), but only the second highest rate of annual production per man employed (736.8 tons). Decided variations are met with in the considerable fluctuations for individual years and in both the anthracite and bituminous coal fields. There has been in the anthracite field a gradual rise in the average production of coal per man employed of from 1.85 tons in 1890 to 2.39 tons in 1908, but in some years the production has been still higher, as, for illustration, in 1899, when it attained to 2.50 tons. In the bituminous fields the average production per man has increased from 2.56 tons in 1890 to 3.34 in 1908, having attained a maximum point of 3.36 in 1906.(*) In a measure, of course, this increased production is the result of the increasing use of coal-cutting machinery and of other labor-saving methods. The relation of work pressure to accident occurrence, particularly in falls of roof and slate, will be subsequently brought out in its proper place.
The method by which coal is mined varies widely in the different States and at different periods of time. No factor has been of greater significance in this respect than the introduction of coalmining machinery. The percentage of bituminous coal mined by machinery is constantly increasing, and within five years there has been an increase from 28.80 per cent in 1904 to 37.52 per cent in 1908.() In some of the States, however, the progress has been much more rapid, while in others, probably because of the opening of seams not suitable for machine mining, there has been a relative decrease in machine production. The largest relative degree of machine use is in Ohio, where 75.37 per cent of all the coal mined in the State in 1908 was mined by machines, against 57.31 per cent mined by this method in 1904. How far, if at all, there may be a direct relation between machine mining and accident occurrence it is impossible to state with accuracy at the present time. Out of 11,569 coal-mining machines in use in 1908 it is reported by the United States Geological Survey that 6,380 were pick machines, 4,992 chainbreast machines, and 197 were long-wall machines. (*) The vast economic importance of coal-cutting machines is indicated by the fact that against 545 machines in use in 1891, cutting or “ producing” 6,211,732 tons of coal, the number in use in 1908 was 11,569, cutting or producing 123,183,334 tons, or 37.52 per cent of the total bituminous product for that year.()
a Mineral Resources of the United States, 1908, Pt. II, p. 47. L'. S. Geological Survey, Washington, 1909.
Idem, p. 45. ° Idem, p. 41.
Mining methods vary, necessarily, according to the nature and character of the coal beds, the depth of mines, and more or less according to local customs and usages. There are no statistics for the United States which give all the necessary information for a full understanding of the conditions under which coal mining is carried on at the present time, but the data for the State of Illinois are suggestive of the method in the statistical presentation of these facts which should be followed in its essentials by the different coal-producing States. Through the cooperation of the state geological survey and the state mine inspectors (there is no chief inspector of mines in Illinois) the geologic seams of coal worked in each mine have been carefully determined and tabulated, so that it is possible, with some difficulty, of course, but it can be done to coordinate the accident risk to the different coal-bearing strata of the State.() Thus, for illustration, the most important coal-bearing strata is geologic seam No. 6, which is mined in 353 out of 922 mines in the State and in 29 counties, producing 29,759,180 tons out of a total production of 49,272,452 tons. The next most important coal-bearing strata is seam
& Mineral Resources of the United States, 1908, Pt. II, p. 50. U. S. Geological Survey, Washington, 1909. Idem, p. 48.
Idem, p. 51. & Twenty-seventh Annual Coal Report of the Illinois Bureau of Labor Statistics, 1908, p. 145.
No. 5, which is mined in 255 mines in 16 counties, producing 11,473,392 tons. The third most important seam is No. 2, which is mined in 167 mines in 22 counties, producing 5,654,924 tons, so that these three seams at the present time constitute practically the entire coal-producing sources of the State. Changes in coal-producing seams, increasing depth of, mines, and alterations in the physical character of the seams can be traced with admirable completeness by this method of statistical presentation from year to year.
The manner of working the coal seams of the State is also presented in complete form in the coal statistics of Illinois. In 1908, out of 922 producing mines, 862, or 93.5 per cent, were worked on the pillar-and-room plan, 51 on the long-wall plan, and 9 by stripping. Of the 51 mines worked on the long-wall plan, which, it is hardly necessary to say, presents essentially different working conditions and mining hazards than the pillar-and-room method, 43 were located in coal seam No. 2. To this interesting information it is possible to add a complete statement of the character of the openings, which vary considerably in the bituminous-coal fields, and it is shown that out of 922 producing mines 620 were entered by shafts, 105 by slopes, and 197 by drifts. All of this information is available for each individual mine, so that a thorough study of the relation of casualties to the physical and geological facts of the industry is possible, but no such extensive analysis has been feasible in the present investigation, which aims rather to present the essential facts of fatal coal-mining accidents for the coal-mining area of the United States as a whole and in certain essential details for particular mining States.
The method of coal mining and the incidence of risk in mining operations is, as has previously been pointed out, conditioned by the nature and character of the coal areas, which are briefly described by Mr. Marius R. Campbell in his report to the National Commission on the Conservation of Natural Resources, and as quoted in part in the report of the United States Geological Survey on the production of coal for 1908, as follows:
(1) The eastern province, which includes all of the bituminous areas of the Appalachian region; the Atlantic coast region, which includes the Triassic fields near Richmond and the Deep and Dan rivers fields of North Carolina, and also the anthracite region of Pennsylvania. (2) The Gulf province, which includes the lignite fields of Alabama, Mississippi, Louisiana, Arkansas, and Texas. (3) The interior province, which includes all the bituminous areas of the Mississippi Valley region and the coal fields of Michigan. This province is subdivided into the eastern region, which embraces the coal fields of Illinois, Indiana, and western Kentucky; the west
* Mineral Resources of the United States, 1908, Pt. II, p. 27. ('. S. Geological Survey, Washington, 1909.