XLVI. 



J. HAYDON CARDEW. 



be left in the pillars after the bords, headings, and drives are 

 constructed shall be as follows: — "Where the depth from the 

 surface does not exceed 200 feet 50%, from 200 to 500 feet in the 

 proportion of 50 to 60%, from 500 to 1,000 feet in the proportion 



of 60 to 70%, etc." 



There is no doubt that in this mine and many others there are 

 large areas of broken mine, the second working of which (that is 

 the pillar working) cannot be successful owing to the extravagant 

 method of robbing the pillars and working easy coal : in the older 

 workings of the mine the proportion of pillars to the whole seam 

 is only 37%. In the Zig Zag colliery the depth is from 200 to 

 300 feet, so that the new rules for the size of pillars are unwittingly 

 very nearly the same as the Chief Inspector advises. Plan No. I 

 shews a portion of the workings more particularly the dip, where 



