large as those where the whole quantity of wind passes in one current through the workings, like Lund-hill; therefore, the expenditure will no doubt be much less.-Father: The mode would be more economical than if the whole of the air passed around the workings in one current; but the danger of loss of life by an explosion would be the same as that of ventilating by one current.

Son: It is clear that an air-gate will not require to be so large, for, say 6,000 feet, or 12,000 feet of air to pass, as for 50,000 or 60,000 feet, and therefore, the expenditure will be much less. But why is the danger of loss of life the same?-Father: Because this mode of ventilation neither divides air nor gas, the gas being conducted in the same way as in the other method I described, from one working part to another, in one continuous route, so that all the gases in the mine become formed, or accumulated, into one large quantity i therefore an explosion in any part of the mine would ignite the whole quantity of gas, the power of such an explosion would affect all parts where the air passed, and cause great loss of life.

Son The mode of ventilating mines by one continuous route is caused, you say, by fixing doors to propel air forward from one working part to another, I wish to know then how this mode of supplying the workings with a mixture of pure and impure air is accomplished ?-Father; It is accom→ plished by fixing regulating doors in the air-passage. you know, will always rush by the nearest route from the down-cast to the up-cast, and regulating doors are fixed in the air-passages to stop the great rush of air, and propel a portion of it into, and around, the longest routes, which would

Air,

otherwise be left without air. The doors are fixed in the openings between the in-take and return air passages, at or near the letters SS.

Son: I shall be glad to know, at a future day, why air rushes around the nearest workings, and the longer route of workings are left destitute of air; but how, father, are regulating doors fixed in mines ?-Father: They are fixed in those air-passages through which the air rushes with great velocity, to take off, or propel such quantities of air as are required for other workings, and are so fixed as not to fill the whole space of the air-passage, but open spaces are left to allow a proper quantity of air to supply other working parts of the mine.

Son: Very good, father; but what other modes of ventilation are adopted ?-Father: Another is, that of conducting the air into the workings after the plan of ventilation adopted by the late John Buddle, Esq., viewer in the North of England.

The Power of an Explosion.

Son: Was Mr. Buddle's plan considered to be a safe mode of ventilation?-Father: I believe it was much thought of in his day; yet it is not a safe mode of ventilation.

Son: What was the mode he adopted?-Father: It was one similar to several modes of ventilation I have seen adopted in mines at this day, and which many managers call dividing the air; yet, it is not what may be called splitting the air. This mode of ventilation is to divide the air into separate parts, for separate groups of miners; after which all those separate parts of air return into the same current again from which they separated. Then again, this one current of a mixture of winds is divided a second time for more groups of miners; after this

1

all the separate winds form one again, and this one mixture of winds passes on further into the extremity of the mine until the said one current requires dividing for other workings of the mine, and so the same is allowed to divide or separate into as many parts as workings, returning and forming one wind after being divided. This mode of ventilation cannot be properly called splitting the air, because the air is allowed to return back into the other portions of the air from which it separated itself, and no working part has a separate distinct wind, as each division is a mixture of winds from the others, with gases collected from the same in each wind. Therefore, as the air is allowed to spread in and through the workings, every part would be affected by an explosion therein; for the gases collected from all parts would be mixed in the said wind in which the explosion might occur. This being the case, the flame of the ignited gas would fly and spread in and through the workings of each part like the electric fluid, carrying death and destruction in its passage. By this it will be seen that this mode of ventilation does not divide or diminish the explosive power (gas), as the explosive gas would be like a combustible train, and, if ignited in any part, would fly through and around all the parts where it circulated. Plan No. 3 is, I believe, a representation of Mr. Buddle's mode of ventilation; by an inspection of it, it will be seen that the air separates ten times in its passage through and around the workings, and the current of air which ventilates the whole mine, is formed into one wind as often as it is divided; by which, all the gas generating from every strata, through the whole mine, is collected into one vast quantity. As to the number of times the air is separated in its passage through, from the down-cast to

the up-cast, see Plan at No. 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. This mode of ventilation, if called a splitting of the air, is not a separate distinct dividing of the gas.

Son: Was this the mode of ventilation you alluded to in your reply to a person in the "Miner," who requested you to inform him the meaning of split winds in mines?-Father: This plan does not show the mode of splitting air, yet it is the one I alluded to in my letter.

Son: Let me see the letter.-Father: Here it is; it will give you a knowledge between this mode and that of ventilating by separate distinct currents.

THE LETTER.

SIR,-In your "Notices to Correspondents" of last week's impression (January 2), I am requested to inform a "Constant Reader" the meaning of "splitting" the air.

My object through life has always been (and I hope will, until my work on earth is finished) to try to better, if possible, my fellow-workman-the miner. When I speak of mine ventilation, it is from a practical knowledge of seeing and doing the work, and not from a knowledge only of theory, reading, and hearing. When I speak of air splitting, I mean separate, distinct currents, and not that kind of splitting which is similar to that which takes place when the wind blows on the surface against a building, the wind being separated by it, and afterwards mixed again; and so the wind is divided and mixed in passing and repassing every building. The above is similar, I say, to the splitting adopted by some managers. They allow the whole of the air to pass in one large current until one portion of the air is propelled by the great friction of the air around one part of the mine, and another portion around another part; and so the said air is allowed to split or divide as it rushes through the mine into as many parts as are working, returning and forming one wind. after it has been divided; therefore, it is not a separate, distinct current or wind, but a mixture of winds,, with gases collected