MODE XII. SLATE. 109 



this rock, which would render enormous clear- 

 ages necessary, and would expose the workmen 

 to great danger from falls of the rock. 



" The principal slate-mine of this country is 

 that of Rimogne, four leagues to the west of 

 Charleville. It is in a hill, of which the centre 

 is primitive, but the skirts are in part covered 

 with beds containing shells. The mouth of the 

 mine is towards the summit ; the bed explored 

 inclines forty degrees to the horizon, so that to 

 advance four feet, you must descend about three 

 feet perpendicular. The workmen call this bed 

 the plate, on account of its form, which is flat 

 and thin, if the extent be considered. Its thick- 

 ness is nevertheless sixty feet ; but its length and 

 breadth are incomparably greater, and their li- 

 mits remain unknown. It has been pursued, by 

 a principal gallery, to the depth of 400 feet j 

 and they have driven many lateral galleries, 

 which are prolonged about two hundred feet, 

 on each side of the main gallery; where are , 

 placed, in succession, twenty-six ladders, for the 

 passage of the workmen, and the carriage of the 

 slate. 



" But in this thickness of 60 feet, there are 

 only 40 of good slate : the remaining 20 of the 

 underpart are full of quartz, and unmanageable. 

 The rock, which forms the immediate roof of the 



