GEOLOGY OF THE HALIFAX HARD BED COAL.* 



By J. Spencer. 



All round the out-crop of the great Yorkshire coal field, ranging in 

 a semi-circle, from Leeds to Denholme, and round by Halifax and 

 Leeds to beyond Sheffield, there are a series of beds of coal, clay, 

 shale, and sandstone, from 500 to 600 feet in thickness, known as 

 the lower coal measures. They are capped by the well-known flag- 

 rock — which is so extensively quarried in this neighbourhood at 

 Ringby, Queensbury, and Northowram — and everywhere form a bold 

 escarpment of several hundred feet in height above the millstone 

 grit country. There is a fine example of the general character of 

 this escarpment in the range of hills from Swill Hill to Ringby, 

 Beacon Hill, Southowram, and the Ainleys. These strata yield two 

 workable beds of coal known as the hard bed coal and the soft bed 

 coal, the latter being the lowest, and at an elevation of about 27 yards 

 above the rough rock, while the former lies 25 yards above that. The 

 difference between these two beds is very remarkable, both on account 

 of their mineral characters and also of their associated strata. The 

 soft bed is a very fair coal, but unfortunately only a thin one, being 

 but 16 inches in thickness, and the character of the enclosing strata 

 is very much the same as the character of those about the middle 

 and upper coal measures. The hard bed is generally a very impure 

 coal, containing a great deal of sulphur in the form of iron pyrites, 

 carbonate of lime, sulphate of lime, &c., and requires great care in 

 freeing it from these impurities before it is fit for use. It is generally 

 about 27 inches in thickness. This coal is the one generally alluded 

 to as the " Halifax coal," and there are so many interesting facts in 

 connection with it, tiiat it is no exaggeration to affirm that it is one 

 of the most important beds, geologically speaking, in the whole of 

 the Yorkshire coal field. In the first place it has for its floor the 

 peculiar and well-known gannister rock — so frequently met with in 

 the millstone grit and Yoredale rocks ; in the next place the coal 

 itself is highly charged in some places with roundish nodules of iron 

 pyrites (brass lumps) and balls of carbonate of lime, both full of 

 vegetable matter — plants broken into fragments. The admirable 

 state of preservation in which these plants are found enables us to 

 affir^m with confidence that they were not only land plants, but that 

 they actually grew on the spot where we now find them. 



Kead at the Ovenden Naturalists' Society. 



