many lives have been lost by it.-Father: Many lost! The number is too great to be told. Your father was left in the world fatherless by it, and, from early life, I have had to make my way throngh the world without the blessing of a parent's care.

Son: I think, father, there was not so great a number of lives lost by explosions in the early days of coal mining as at the present time by the same mode. Can you tell why there was not?-Father: Because they had only limited means of getting out coal to the surface, they had only a limited number of works, they had only a limited number of persons employed in the works, and only limited means of ventilating them. 'Therefore, if they had only a limited number of persons, of means, of works, and of air, they had not so much gas in the air at the time of an explosion; that is to say, they had less air, and they had less works for the air to pass around; therefore they had less explosive gas in the air when it ignited; and if less gas, the power of the explosion would be less when it did take place; and if the explosive power were less, and there was a less number of works, there would be a less number of persons lost at the time of an explosion. Therefore, by the same mode of ventilation there was not so great a number of · persons lost as now.

The Danger of one Mode of Ventilation, and the Safety of another.

Son: Is not air conducted from one working part to another, clearing away the gas in its passage, from all places in its route?-Father: Some managers adopt that mode for the ventilation of mines, but it is neither safe nor profitable, for miner or master.]

Son; Why not safe and profitable ?-Father: Because the mode requires many doors fixing in the tram-gates to impel air forward from one working to another, and to allow waggons to pass and repass with coal from the workings. It is unsafe, because, if one door be left open, all the lives would be jeopardised; unsafe, because, if one place be affected, all the miners are in danger; unsafe, because explosive gas, conducted from all parts of the mine, will make a large quantity when col lected; and, therefore, the power of the explosion will be very great when it does take place; unsafe, because an explosion in any one part would affect the whole mine. There is expense, too, in making and keeping air-gates large enough to allow the passage of sufficient air to take the gases away from all the separate working-places; expense in making a great number of doors; expense in fixing them; expense in opening and closing them to allow waggons to pass and repass; expense in the furnace expenditure of coal, as a great friction of the air is caused by taking a large quantity into and around so many working-places; expense in destroying the whole workings if so large a quantity of gas become ignited; expense in day-wage work, &c., to make all good after; and expense in making coffins for the many men who have lost their lives from an explosion. A

Son: If air be conducted, then, from one place to another it it is not safe?-Father: No; As may be seen by the mode of ventilation adopted at Lund-hill, all the gases generated from the strata in the whole mine are collected in the air, as it passes onward from place to place, until the accumulation of gas becomes so great that an awful explosion often takes place.

Son: I wish to see, father, a little clearer, as I do not under

stand it properly.-Father: Well, suppose five separate groups of miners are working where so much explosive gas accumulates that each place requires 6,000 feet of air per minute for ventilating purposes. Now, if all the five currents of air make one, and the 30,000 feet pass through all the workings in one continuous route, all the five parts will be affected by an explosion, because all the separate working parts accumulate gas in the draught in which the explosion takes. place, and as all are ventilated by it, all are affected in the same manner. Among the first group of miners all the air enters, after which it leaves that group or place and passes on to the second group, from them to the third, from them it proceeds to the fourth, and lastly to the fifth group. In the first group the men are well ventilated, and may be considered safe, providing that air and gas be not allowed to pass over a burning fire or furnace. In the second group they are less safe, from the fact that all the fire-damp accumulated in the first group goes directly in a current upon the second group; then it proceeds to the third, from them it passes on, with the gases accumulated in its passage, to the fourth group; and then onward the adulterated current goes to the fifth group. Who, indeed, does not see that the miners in the fourth and fifth positions are liable at any moment to be destroyed by an explosion of fire-damp, unless the greatest caution be exercised? One part of the mine would be filled with raging flames, and the men scorched to death by the burning gases; in another they would be killed instantaneously by the expansion of the hot air and gas, or suffocated by the noxious gases which fill all parts of a mine after an explosion.

Son: There are other ways or modes of ventilating mines, you say, than the one adopted at Lund-hill? The mode of

ventilation adopted there was that of conducting the whole current of air around in one passage.-Father: Yes, there are other ways of ventilation. The air is conducted by another mode in the following manner:-One portion of it is conducted pure into one working place; after ventilating the said place, and the air has become impure with gases collected, then a fresh supply of pure air is mixed with it to ventilate another place; and in like manner this mixture of pure and impure air takes place always when each working place is ventilated; and so the air passes on, with all the gases in the mine accumulated in it from every working part, until it discharges itself at the top of the up-cast.

Son: Will plan No. 2 show this mode of ventilation by which working-places are supplied with a mixture of pure and impure air?-Father: Yes. The points of the arrows on the plan show the passage of the air through the workings. When the air first enters at the down-cast, it passes direct to No. 7 working-place; after ventilating this place it is supplied with fresh air for the ventilation of No. 6 working-place, the mixture taking place at the letter S (see plan), and, in like manner, all the other working parts are ventilated with a mixture of pure and impure air; the mixture takes place for all parts at the letters S S.

Son: Is this mode adopted for the safety of miners?— Father: Those persons who adopt such a mode believe it to be for the good and safety of miners, and economy for the employer.

Son: By this mode, air-gates, I see, do not require to be as