BAROMETER AND THERMOMETER AS APPLIED TO MINING.
BY JOHN WILLIAMSON.

Mr. Fairley in his paper gives the opinions of the Inspectors of Mines on the vicissitudes of the weather. In the closing remarks of his paper he says:-"In no case do the reports give any encouragement to the theory of a connexion between the vicissitudes of the weather and the occurrence of explosions of fire-damp; when an opinion is given by the Inspectors it is generally against this theory. As a barometer, a body of fire-damp is more sensitive than anything else, and any warning that a ventilating engineer may receive from meteorologists outside cannot be of practical use as regards danger from gas."

When it is said that the reports of the Inspectors give no encouragement to the theory of a connexion between the vicissitudes of the weather and the occurrence of explosions of fire-damp, have we to understand that in the opinion of the Inspectors the changes of the weather causing a falling barometer have never been the means of producing large bodies of gas and explosion?

It seems when they give an opinion it is generally against this theory. The writer thinks it is understood that the vicissitudes of the weather causing a low barometer will not produce an explosion in a well-ventilated mine, and where proper precaution is taken; but it is possible for an explosion to take place with a falling barometer in mines containing bodies of fire-damp, and where there is defective ventilation, and a want of proper precaution, the opening of doors or the derangement of brattice or air pipes in some mines is sufficient to cause an accumulation of gas, even with a high barometer, and produce explosions.

Then," as a barometer, a body of fire-damp is more sensitive than anything else, and any warning that a ventilating engineer may receive from meteorologists outside cannot be of practical use as regards danger from gas." As to a body of firedamp, it would not be a prudent thing for managers to permit a body of gas to exist for the purpose of being used as a sensitive barometer.

It is a well-known fact that the rising and falling of the barometer invariably causes bodies of gas to increase and diminish in bulk.

The late Sir Warington Smyth in his treatise on “Coal and Coal-Mining" (page 204), says: "The evolution of gases from the coal is greatly affected by the pressure of the atmosphere, a notably larger amount being emitted when the barometer is low; and hence that instrument becomes a useful adjunct in judging of the amount of the ventilation needed at different times."

It may be said that the opinion of the Inspectors is, that if the mines are properly ventilated. and proper precautions are taken, the changes of the weather are not in themselves sufficient to produce an explosion. Then, as to warnings from meteorologists: a prudent manager would not consider it necessary to wait for

warnings from meteorologists if the movement of the barometer at the mine had proper attention. The conditions of mines vary, and are only known by the manager, not by the meteorologist. If a meteorologist can predict so far as to say, we may expect changeable and disturbed weather, and there is every probability of a falling barometer, the writer does not think this at all objectionable. It may be looked at in another light. The writer thinks it may confirm the opinion the manager has formed from his knowledge of the movements of his own barometer. It is not from the point at which the mercury may stand that a judgment of the state of the weather may be formed, but also from its rising and falling, and from the movements of immediately preceding days as well as hours, keeping in mind effects of change of direction, and dryness or moisture, as well as alteration of force of wind.

In general, wind affects the barometer more than rain, and temperature is influenced by wind. Just before great changes the barometer in the mine rises, whilst the barometer at the surface falls, with considerable fall of temperature at the surface only.

In the writer's opinion it is not sufficient to simply have a barometer at the surface. For the proper guidance of a colliery manager it is necessary to have a barometer in the furthermost part of the underground workings; readings to be taken by competent men frequently, and properly recorded. Competent men who carefully watch the movements of the barometer are always prepared to caution the workmen and inform them when great changes are approaching.

The best mode of dealing with abnormal conditions of the atmosphere un. doubtedly is to prevent, as far as possible, accumulations of gas and an explosion by efficient ventilation, and to make use of some of the preventives, such as not to allow accumulations of inflammable gas in any part of the mine; only to allow blasting when the workings are free from gas, and where there are no indications of gas on the flame; to strictly prohibit blasting fast, and only to permit blasting to be done by order of properly qualified men. Blasting ought to be under the control of the most practical and trustworthy men.

There are few colliery managers who do not believe that a falling barometer is calculated to produce more gas than when the barometer is high, and it is well understood that colliery explosions have taken place with both low and high barometers. The explosions with a high barometer might probably be due to accumulations of gas produced by a low barometer and left lurking in some unventilated place.

The barometers and thermometers fixed at mines are to be frequently observed and their movements recorded. A prudent manager will not wait for the barometer to fall to a low point nor a report from some meteorologist before he acquaints his officials of the fact, but will, as soon as he finds the barometer move, take such steps as are necessary for the safety of the mine. There are certain natural laws, such as chemical changes caused by more or less heat, electrical

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action, or mere gravitation, which govern the movements of both the barometer and thermometer, and, as a rule, these laws are certain in their action. If all the movements of the barometer and thermometer and the points of the wind, etc., are properly recorded and a proper chart kept, such information ought to be of great service to a colliery manager.

It has been found, when the wind was from the south or south-west and the barometer low that furnace ventilation was more difficult than when the wind was from any other point. The furnaceman could tell you when the barometer was low, as it caused him more work to keep up the regular quantity of air.

As to the value of the barometer and thermometer in connexion with mining, we may refer to the Mines Regulation Act, where it says, "A barometer and thermometer shall be placed above-ground in a conspicuous position near the entrance to the mine." This was embodied in the Mines Regulation Act from suggestions made by eminent practical mining engineers. The late Mr. J. T. Woodhouse was always particular in ordering the use of barometers and thermometers at all the mines he had to do with, and he was most particular in seeing that the furnacemen were supplied with these instruments, and to show how much Mr. Woodhouse appreciated these instruments he would insist upon having the very best, and he would have them graduated in such a manner as to show the furnaceman when to "fire up," etc.

It is a fact that when bodies of gas have been present in goaves, and resting just above the roof of the mine, the gas has settled down when the barometer was falling, and filled the miner's lamp (hanging on a prop) with flame, the miner being quite unconscious of what was going on until he either heard the cracking noise or smelt the burning gas. This was a frequent occurrence.

We have in the Report of the Accidents in Mines Commission the minutes of evidence of Mr. Wales, Mr. Hall, and others, giving their experience of the uses of the barometer in mines:

"Mr. Wales-3,095-Believes that gas exudes in larger quantities with a low barometer. 3,096—We find in most collieries a much larger cap with a low barometer than with a high barometer. 3,097-I have observed this frequently.

"Mr. Hall-3,557-Gas comes off much more freely with a low barometer. 3,558-Gas comes off at goaves with a low barometer. 3,559-I have frequently tested stoppings connected with old goaves, and gone to the pipe when the glass has been high and when the glass has been low, and sometimes the pressure was in-over when the glass was high, but always when low the gas has been coming out very freely. 3,561-I think frequent observations of the barometer are an advantage. 3,565-I am satisfied that with a low barometer very much more gas comes into the air-ways. 3,648-Gas comes off in larger quantities with a low barometer, but still accidents occur with a high barometer. They have occurred.

"Mr. Bagot-4,365-6-My experience of barometers and blowers, and particularly barometers in explosions is, that it is after the barometer has fallen and begun to rise again that they occur. 4,367-When the barometer is low, gas is more liable to blow. 4,417-If you rely upon the barometer and neglect ventilation it would be a most serious question.

“Mr. Galloway-13,672-Does not think the indications of the barometer too sluggish for mines. 13,677-You are still inclined to infer that there is sufficient connexion observed between the phenomena underground and the changes of the weather to make it important that the manager should keep a strict eye upon the indications that are presented to him in that way? I do."

Some years ago experiments were made by the writer with the barometer, thermometer, and hygrometer in mines, and frequently it was found that a body of gas thickened with a falling barometer and a slightly increased temperature; the variation of the barometer in the mine is much more than that of the thermometer. The temperature of many mines in the workings does not vary during the year more than about two degrees.

The hygrometer shows the moisture of the air up to a certain point, and is not considered of much importance in connexion with mining on account of the uncertainty of its action. For the air of mines is, as a rule, more or less charged with moisture.

At a colliery in the county of Durham, where there was much water, the beam of the pumping engine broke and the mine was drowned up for some time; there was only one shaft, which was divided by brattice to form an upcast and a downcast shaft; the water rose in the shaft for 35 yards above the inset. In one of the districts where there were workings on the top of a large fault much gas was made. During the stoppage of the pumps, and when the water was 35 yards up the shaft there were several water or gas blasts, blowing the water to the top of the shaft. This always took place when the barometer got very low, and was due to pent-up gas; all fire lamps, and open lights were, therefore, removed from about the top of the shaft. Many other similar cases could be given.

Within a short distance of this colliery a water-level was driven partly in sand, gravel, and clay; after driving about 200 yards there was great difficulty in ventilating the tunnel, and the exuding black-damp or carbonic acid gas was very great when the barometer was low, often causing a suspension of the work. The tunnel was of an egg-shape, and 4 feet 6 inches high; the air boxes were 15 inches by 8 inches laid on the bottom of the arch, and connected with a small furnace at the entrance of the tunnel; the tram rails being laid on them (the boxes). The sudden filling of the tunnel with carbonic acid gas as the work advanced was remarkable, sometimes the workmen were in a state of asphyxia before they could get out, and as soon as the barometer began to rise, and the wind got to the north or north-west the carbonic acid gas disappeared in as little time as it came, and when

the flame of the candle was applied to any of the crevices in the gravel, where the carbonic acid had came out, it was pulled or sucked in.

In North Staffordshire, from the bottom of a shaft 300 yards in depth, a rock-head or crut was driven for the purpose of recovering several seams of coal which lay at an angle of 45 degs. to 50 degs.

In the driving of the crut the coal seams were intersected, and one of the seams made a large quantity of gas, into which a head was driven for about 5 yards; at 3 feet within this headway a 14-inch brick stopping was put in with an 13-inch pipe inserted. The stopping was hermetically sealed. The pipe was carried to the shaft bottom and fixed, with the end turned up the shaft, when the gas coming from the headway was ignited, and gave a flame about 2 feet long which lighted up the shaft bottom.

Sometimes the closing of the separation doors, or a sudden drop of the cage in the shaft bottom would extinguish the light, and at other times the flame was with difficulty blown out. The writer gave some attention to this, and found the extinction of the light was due to changes of the barometer. When the barometer was high there was much less light, and it was more easily extinguished than when the barometer was low, with a much larger flame.

It is well known that the barometer shows the weight or tension of air, the thermometer heat and cold, or temperature, and the wet thermometer compared with a dry one, the degree of moisture or dampness. If any good has to result from the use of these instruments in connexion with mining there must be a more elaborate and methodical dealing with them. We appear to know very little about their proper value. What appears to be known is that a falling barometer produces more gas, and increases bodies of gas, and in some mines (especially old mines) it produces black-damp or stythe.

Within recent years the proper use of the barometer and thermometer is better understood on the surface. Where is the captain of a ship who would think of going to sea without these instruments? By the use of a good reliable barometer a ship captain can invariably foretell the coming weather. It is clear that the uses of these instruments are better understood on the surface than in the mine; then, if the barometer and thermometer are of so much value at the surface, there is nothing in the writer's opinion to prevent them from being equally so for the mine, if they could have the same amount of attention given in the mine as at the surface.

Mr. W. B. SCOTT said that to properly connect the President's paper and Mr. Fairley's paper it would be necessary to add to the latter a statement of the positions of the barometer at the time of the explosions, because on the one hand they had a statement of explosions in different districts, and on the other hand they had the President's statement of opinion that the barometer had something to do