19. The company inspector or fire boss must examine every place in his district before the men are permitted to enter. He should first test each place for gas, then test the roof with a rod heavy enough for him to detect, by sound or feeling, any vibration of the roof. He should bar down any very loose pieces or "fence off" the dangerous place until he has completed his round and returned with some one to help him. Larger pieces that seem dangerous should be marked with chalk for barring down or timbering.

20. A company inspector, fire boss, or district boss should station himself at a designated place where all men who work in his district pass when going in at the beginning of the shift, so that he can notify those going to places that require barring or timbering.

21. An inspector or boss should not rely on his memory but should make a record in a memorandum book and hand it to the foreman or face boss or bosses of that district to transfer to memorandum books that each will keep. A report should also be made and sent to the responsible official of any shortage of timber supplies in the district.

22. Each miner on entering his working place should "sound" the roof and feel with the hand, or with another bar if the roof is high, whether it vibrates when struck. He should put up posts or timbers in the places marked or bar down the roof.66a

23. Picks should not be used to pull down roof, for a falling piece is liable to catch the man using the pick. The foreman should see that every miner has a suitable bar.

24. After the roof is made secure miners or loaders must bar off loose pieces on the coal face; they should be especially careful if the face is over 6 feet high.

25. If the face is very high-say, over 8 feet and seems at all liable to slip off, sprags or props should be set against it until the loose coal has been mined off. Friable coal which has been undercut should be spragged or blocked to keep it from rolling over on the

men.

26. Timbermen must use plenty of temporary posts in putting up timber until the permanent timber is in place. When heavy collars or beams are being put up, temporary bracing must be used to keep them from rolling over before they are secured in place.

27. Lagging should be used freely where the roof or ribs are scaly or friable; to put it up takes little time, and it is especially valuable for preventing falls along entries. A man rarely gets caught through the breaking of timber, as he is warned by the cracking, but a great many accidents from falls of small slabs would have been prevented by lagging.

66a Rice, G. S., Accidents from Falls of Roof and Coal: Miners' Circ. 9, Bureau of Mines, 1912, 18 pp.

28. Large mines would lessen their accidents from falls and effect direct economy in timber by employing a timberman instructor, who would constantly go about the mine showing miners and less experienced timbermen the right way of timbering.

29. In conclusion, falls cause nearly half the deaths and injuries in mines, and virtually all these accidents would be prevented by adequate timbering. Although the miner may be held responsible for any injury received through failure to timber his place properly, the company through its foremen is morally responsible for the character of the timbering and for having the timber properly used.

The Bureau of Mines is now making special investigations of the causes of accidents from falls of roof and coal. A similar investigation, entitled "Support of Ground," has been carried on for some years in Great Britain by the Safety in Mines Research Board.

HAULAGE ACCIDENTS

Haulage accidents in coal mines usually stand second only to falls of roof as a cause of death, the number ranging from 341 to 506 annually between 1917 and 1924. Statistics are not available as to the number of injuries from haulage accidents, yet there is little question but that the proportion of injuries to deaths is larger than for any other principal cause of mine accidents.

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As Table 4 indicates, the largest number of individual accidents are from two causes, run over by car or locomotive" and "caught between car and rib." These two represent 60 to 70 per cent of all haulage accidents underground. The use of main haulage ways for travel of all the mine personnel furthers many accidents of these two types and can generally be avoided by having a separate manway.

Conditions in many old mines make avoidance of travel on main haulage roads impossible, and in entries off which rooms turn it can not be avoided. Under the latter circumstances it is important to have enough clearance between the moving cars and one rib and to give suitable warning of the approach of trips. Such warning might be by an automatic bell on the locomotive or on the head car of a trip hauled by rope. The bell could easily be contrived to be operated by a mechanical or electrical device (the latter actuated by a storage battery).

Many accidents are caused by men being caught while coupling or uncoupling cars. Here, again, the clearance and the character of the coupling are important factors. Care in the handling of trains of cars during coupling is important. Large, heavy cars should have automatic couplers.

Another class of haulage accidents is incident to the spragging or unspragging of car wheels in a contracted space between the cars and the rib. Here any piece of coal, rock, or loose timber piled at the side may cause a man to stumble and get caught. The remedy is to keep the passage cleaned up, to have more clearance, and to use sideoperated brakes instead of sprags. Accidents of these classes are largely preventable by proper layout of the tracks and switches, use of the best design of mine cars, and good organization.

Runaway cars or trips cause the next largest number of mine-car accidents. A very large proportion of such accidents occurs in dipping beds. The remedies are to install automatic catches or derailing switches at the top of every slope and to use gong signals if a trip does get away.

PRECAUTIONS

On man trips on slopes automatic catches of some kind should be used. It would be desirable to have them operate for a descending trip when the speed exceeds 15 miles an hour. For ascending trips strong "dogs" or catching irons are much used; for descending trips several types have been designed but are little used.

Where men are lowered or hoisted in ordinary car trips it is highly important that a second rope shall be fastened the full length of the trip over the top of it and secured by a clip to the hoisting rope above the socket.

An alternative method is the use of safety chains for coupling the cars. Although this precaution provides for breakage of the regular coupling, it does not provide, as does the safety rope, for breakage of the socket or the attachments to the first car.

On main roads and slopes the signal wires should be within ready reach of the trip rider.

Hoisting-engine drum brakes, gravity-plane brakes, ropes, and fastenings should be inspected and tested by trial at least once a day before the principal shift is lowered down the slope.

In secondary slope roads or gravity inclines there should always be at the top of the slope or incline automatic stop blocks, released by the man at the top after signals are interchanged with the hoisting or gravity-incline engineer.

In dipping or raising rooms or headings, where the cars are lowered by rope and brake in balance, the car at the face of the room or heading should always be securely blocked in such a way that it can not be released accidentally before it is ready.

Electric or pull-bell signals are essential for the safe operation of any slope or incline on which the cars are handled by gravity or the grade is sufficient to start the cars running if they are not blocked.

Where men are hauled to and from their working places in trains of cars by electric-trolley locomotives, it is highly important that the trolley wires shall be far enough to one side and always on the same side, that they may be clear of the men in the cars.

Explosives should never be carried on man trips; serious disasters have been so caused.

Men should never be permitted to ride on top of loaded cars; this causes many accidents. No one should be permitted to ride on an electric locomotive except the motorman and the trip rider, if there is a seat for the latter.

Good lighting is an essential in preventing haulage accidents. Good lighting not only refers to the lights of the men who are authorized to travel haulage ways and of miners who are using the entry off which the working places turn, but also to locomotive lights and the head car of a rope trip.

Every trip of cars should have a rear light so that, if a trip breaks apart on a grade, the men on the roadway or on a following motor trip will see the runaway or detached cars.

Every mule or horse should have an electric light on its collar.
All haulage lights should be of permissible type.

INSTALLATIONS RECOMMENDED FOR SAFETY

In main haulage ways there should be a clearance of not less than 3 feet between the farthest projecting point on the side of the car and the rib. This clearance space should always be on the same side of the entry and kept free from débris. In addition, there should be refuge holes on slope roads, inclines, or wherever State regulations may call for them; such holes should not be more than 100 feet apart and as much less as the State law requires. Even though there is clearance for travel under ordinary conditions a runaway trip or car may jump the track; therefore refuge holes are needed. They should be whitewashed or otherwise clearly marked, should be kept free from all obstructions, and should be 62 feet high, or not lower than the height of the haulage way if that is less than 612 feet.

Trolley wires and power lines should always be placed on the side of the haulage way opposite from the traveling side. Where men must pass or cross underneath, trolley wires should be not less than 62 feet above the rail measured to the sag of wire between supports, or else should be protected by boards or inverted troughs. The trolley wire should be sectionalized by switches in as short sections as practicable (see proposed standard electric practices on p. 76). It is recommended that the voltage of the trolley circuits be not greater than 275 volts, as then there is less danger of men being killed by shock if they touch the trolley wire.

Men should carry tools in the hand and not on the shoulder while in those parts of a mine where there are power lines.

Well-laid, well-ballasted tracks having heavy rails, fishplates, and close-laid ties are important features in preventing haulage accidents. Mine cars are constantly being improved by safer running gear and good brakes, and should be arranged with safe couplings, preferably those that are automatic. The Bureau of Mines recommends tight-end cars, not only to lessen spillage of coal which is ground to dust on the rails, but also to reduce the number of derailment accidents caused by coal on the track.

Cars should be constructed to avoid sharp corners and projections that may catch men or animals. Projecting bolts should be avoided; flat-headed rivets are preferable. To lessen danger of injury to men it is better to place angle-iron side frames inside than outside the