404 



fore, confidently recommended that an air-drift should be made 

 from each separate panel, communicating with the bottom of 

 the downcast shaft. Now the advantage of this is manifest, 

 for besides the greater quantity of air actually introduced by 

 thus splitting the current, the destruction of life consequent 

 upon an explosion is thereby diminished, provided the panels 

 are of moderate size and do not communicate with one ano- 

 ther, as to render it impossible to escape to the bottom of the 

 pit without passing through air affected with the after damp. 

 It may be true that to split the current weakens the force of 

 it, but it does not, if the distance to be travelled is shortened, 

 for the sum of the velocity of the divided currents (and, 

 therefore, the quantity of air admitted into the. mine) will 

 be much greater than that of the whole united current, 

 since the fire is exerted in a great ratio upon the shorter 

 distances. 



It is an easy thing to have rapid currents in the larger air 

 courses, but the difficulty is to have currents of pure air in 

 the benks, slits, thirlings, &c. ; and the further distance any 

 air travels the more impure it becomes, because it is progres- 

 sively collecting bad air. 



In order to divide the air, and use it in the workings in 

 separate divisions, and in the long or Yorkshire method, 

 several plans might be adopted. Suppose there are 24 henks 

 on each side of the pits to be ventilated, one-half of the air 

 would go to those on the one side, and the other half to the 

 other. These halves might again each be sub-divided into 

 three portions, so that eight benks would be ventilated by 

 every one of the sub-divisions. ( See plate 1.) The air would 

 thus be divided into six portions, each serving and ventilating 

 its own compartment ; and if an accident should occur in one, 

 only the persons suffer which are in it, and the air will be 

 renewed six times in a given time, instead of once, as on the 

 present system. The only objection is the small expense of 



