ber. Sketches of these barricades are shown in figures 29 and 30. A sample of the air in the barricaded area where the bodies were found contained 0.21 percent carbon monoxide, 5.71 percent carbon

FIGURE 31.-Message left by entombed miners at face of main crosscut in Argonaut mine.

dioxide, and 14.18 percent oxygen-an atmosphere deadly to any one forced to remain in it for any considerable period. The only message the miners left was that shown in figure 31, which had been written

with the smoke flame of a carbide lamp on the slate face of the main crosscut.

It appears highly probable that before these men had an opportunity to complete the barricade the atmosphere of the barricaded region had been fairly badly contaminated by poisonous gases from the fire; and the evidence obtained indicated that all of the men within the barricade were dead within a few hours after the second or inner barricade was partly completed. In this instance the men failed to avail themselves of a very vital protective measure, namely, short-circuiting of the ventilating current; however, while this might have saved them temporarily, the fact that they were not reached for 3 weeks makes it probable that they would have perished long before help arrived.

NORTH BUTTE MINE

During the fire in the Granite Mountain shaft of the North Butte copper mine at Butte, Mont., on June 8, 1917, in which 163 lives were lost, there were 3 instances of barricading-1 successful, 1 partly successful, and 1 a failure; 31 lives were saved and 25 lost.

Twenty-nine men from various places had gathered at the 2,400-foot level; being unable to get out, they decided to build a bulkhead in the 2,471 crosscut, one of the shift bosses taking charge of the project. Before going in they procured saws, axes, shovels, chute lagging, canvas pipe, nails, a partly filled water keg, and other materials. They chose a point about 250 feet from the face of the drift, which gave them approximately 9,000 cubic feet of air. A Leyner drill had been set up near the face, and compressed air was available, but the men did not use it because they feared it might contain fumes from the fire, though such contamination was almost impossible. In erecting the bulkhead the miners built a form somewhat like those used in building concrete stoppings or brattices in mines. A space of about 8 inches was left between the faces of the boards, which were placed horizontally, and this space was filled with fine, dry dirt. Holes between the boards and around the edge of the forms were chinked with canvas pipe, clothing, etc. Four men worked at a time, and the bulkhead was completed in less than an hour. A hole was left near the side of the crosscut to be used to test the outside air and then to be closed by inserting into it a man's jumper.

To attract outside attention after they had closed themselves in, the men took turns at rapping on the air pipe and track rails near the bulkhead. After rapping, each man walked toward the end of the crosscut and thus kept the air well-stirred; this very probably helped materially to save the lives of the entrapped men. At the end of 24 hours neither a match nor a carbide lamp would burn. The water was exhausted during the last 10 or 12 hours of the 36 hours of imprisonment. After 36 hours the bulkhead was broken down, and 25 of the men walked in more or less fresh air to a shaft and were taken to the surface; the other 4, including the shift boss who had acted as leader in the early stages of the bulkheading, took the wrong direction in attempting to reach a certain air shaft, were overcome by gas, and died.

On the 2,200-foot level eight men retreated into the 2,254 crosscut; this was about 400 feet long, with a 50-foot branch off it. A Leyner

drill had been set up near the face, and near by was a partly filled 50-gallon water tank. While retreating into the crosscut these men carried materials similar to those carried by the men in the 2,400-foot level, and at 80 feet from the face they built a bulkhead by several hours of work. As in the previous instance, these men were under

FIGURE 32.-A, Bulkhead in 2,254 crosscut, North Butte mine, behind which eight men were entombed for 55 hours. B, Bulkhead in 2,254 crosscut, North Butte mine, from outside bulkheaded area.

the leadership of a shift boss and (also as before) the shift boss lost his life, though six of the eight men within the barricade were saved. Figure 32, A and B, shows the outside and the inside of the bulkhead.

Round posts were placed across the floor, and a shorter piece of timber was wedged along the top of the crosscut above the posts on

the floor; other timbers were placed between and were wedged to the sides. Before the middle timbers were placed, inch boards were nailed vertically to the outside of the two round posts, and on the inside of these boards canvas ventilating tubing and clothing were nailed. After the boards and canvas were placed the timbers were put in and wedged, and the spaces between were filled with mud, of which there was a plentiful supply.

It was lucky that compressed air was available, for a jet of air was used to force back the gas, which was moving toward the men while they were building the bulkhead or brattice. A thorough search was made for leaks in the finished bulkhead as soon as it was completed. Finally all lights except a candle were extinguished to conserve the oxygen. The men took turns rapping on the air pipe to signal possible rescuers. Six of the eight men lived for 50 hours behind this barricade, but they were unconscious when rescued.

When the bulkhead or barricade was torn down two dead men were found lying against it, one being the shift boss, who had acted as leader. The other six were lying unconscious, huddled together, a few feet away from the bulkhead, and after they were taken out and sent to the hospital some of the rescuers went inside the barricaded region, where the air was found to be of such character that it could be breathed without hazard. There is abundant reason for the belief that those eight men kept too close together and remained quiet, thereby unduly consuming the oxygen in the air near the bulkhead and not taking advantage of the purer air in the interior of the barricaded region.

On the 2,600-foot level 19 men tried to shut themselves in but were found dead because they had failed to notice an open manway back of the bulkhead they had built, between the 2,600- and 2,800foot levels. Moreover, the drift was in broken ground, stopped from below and back-filled with loose material through which gas could pass readily. In all of these instances of barricading at the North Butte fire the temperature within the barricaded region exceeded 80° F., and the relative humidity was almost 100 percent, an atmos pheric condition very uncomfortable. This high-temperature, highhumidity air is extremely uncomfortable and debilitating when it is stagnant, as it would be within the bulkheaded region, and this would be true even when the air was chemically pure; each man would consume about one-half cubic foot of oxygen per hour and replace it with about the same amount of carbon dioxide; this very probably was done almost wholly within about 10 or 15 feet from the bulkhead and soon created an atmospheric condition that killed two men and caused the other six to become unconscious.

CARDINAL MINE

Between 8 and 9 a. m., December 4, 1925, fire started in the compressor house, change house, and blacksmith shop at the entrance to the Cardinal tunnel of the Fairview Mining Co. near Nederland, Colo. (Lead ore, carrying considerable gold and silver and a little copper, is mined at the rate of 125 tons a day. The mine has been worked over a period of 30 years.) As shown in figure 33, the tunnel was heavily timbered for 100 feet or more, beyond which it was in solid rock.

The fire spread to the timbers and thus imprisoned 20 men, including a contractor and a shift boss, and 2 horses in the mine. A trammer discovered smoke in the tunnel, unhitched his horse (the horse was later found dead), and turned back into the mine at the junction of the tunnel and drift, where the other men were congregating. (See fig. 33.) The contractor and shift boss decided to build a barricade near a chute from No. 12 stope. This bulkhead consisted of a couple of timbers (for sets), some boards, mud, and clothes. Several men were more or less overcome by the smoke while erecting the barricade. In all, 20 men and one horse were sealed in the drift, which had open stopes and drifts above it. As they feared that the fan might be started by somebody on the outside, the miners cut the fan ventilation tubing near the barricade.

FIGURE 33.-Plan of Cardinal mine, showing where 20 men erected a barricade after a fire on the surface.

Meanwhile, outside of the tunnel a fire-fighting and rescue crew attempted to extinguish the fire and get into the mine. As this was impossible at the tunnel portal, at 9:00 p. m. that night they entered by way of the air shaft. One man wore a 1-hour oxygen breathing apparatus, but three others are said to have entered without respiratory protection. The four reached the barricade and tapped on the air pipe to notify the men behind of their presence. The rescuers then pulled off two or three of the boards of the barricade, when smoke poured in through the opening. The three rescuers without apparatus collapsed, and two were pulled inside the barricade by those behind; one was unconscious for 2 hours yet recovered, but the other died. After this, the contractor and another imprisoned miner dashed for the outside with the third unprotected rescuer and the one with apparatus; the last probably saved the lives of the contractor and the unprotected rescuer. The other miner was found dead. Finally, the fire was sealed off, the smoke cleared from the tunnel, and the barricaded miners walked out or were hauled out in mine cars by the horse they had taken in with them. They were imprisoned for 16 hours and, apart from exposure to cold, were not seriously harmed.

In this instance little time was lost in deciding upon the erection and place for a barricade and it was built quickly. There was enough