UNDERGROUND WORKINGS OF A WESTERN COLLIERY. XLVII. 



coal-mining is now in progress, it also shews the engine plane, 

 shafts, etc. 



Whether the pillar and stall system of working the coal in this 

 colliery is the best or not is open to discussion, and a few descrip- 

 tive remarks on the general methods of laying out underground 

 workings may be of interest. First it may be stated that the 

 great object to be kept in view in all coalmining is the obtaining 

 of the greatest quantity of coal, in the best condition and with 

 the least expenditure of money; and in order to attain that end 

 the system to be adopted is a question of great importance, and 

 one deserving the careful consideration of the Engineer. 



Generally speaking there are two systems, but they have modi- 

 fications, one being known as the "Pillar and Stall" and the other 

 as the "Long Wall," both systems have their respective advocates, 

 and their relative merits are a favourite subject of dispute, some- 

 thing like the Telford and McAdam systems of roadmaking or the 

 battle of the railway gauges, but they each have peculiar advan- 

 tages under certain circumstances. 



In the pillar and stall system, excavations called bords are 

 driven through the coal parallel to one another and at certain 

 intervals apart, so as to leave a rib of coal between them to sup- 

 port the roof; the excavations are made as wide as the strength 

 of the roof will permit. At right angles to these, another set of 

 excavations are driven parallel to one another and narrower than 

 the bords; the sets of excavations crossing one another leaves in 

 the seam rectangular blocks of coal called pillars. 



Now coal is divided into cubes by joints or cleavage planes 

 running perpendicularly to one another, the most defined joint is 

 called the "cleat" and its surface is called the "face" in opposition 

 to the least defined plane which is called the "back or end" and 

 in pillar and stall working the bords are driven at right angles to 

 the cleat so as to obtain the advantage of the pressure of the roof 

 which tends to cleave the coal on the principal planes of cleavage, 

 that is to say, the seam has a tendency to break up under the 



