STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 503 



Coal seams are rarely single, usually are divided into benches by 

 partings of clay or sandstone which may vary greatly in thickness^ 

 though ordinarily the variations are within narrow limits. At times 

 they are great enough to render the identification of seams more 

 than perplexing. The Beeston Coal has its two benches in contact 

 at Beeston, but within a short distance they are separated by an 

 interval of 30 feet. Three seams of the Brown Metals Group show 

 notable changes in relative positions ; the interval between Number 

 I and Number 2 is 6 inches to 56 feet, and that from Number 2 to 

 Number 3 is from 12 to 66 feet. Other illustrations are noted, but 

 these suffice for illustration.^"^ 



Contemporaneous erosion is by no means unusual and at some 

 localities its work was extensive. In this, one may see evidence of 

 areal changes of level. Near Penistone, a tunnel has disclosed 

 proof that the region was exposed to denudation for a time in the 

 early part of the Middle Coal Measures. A hill of Coal Measure 

 sandstone remained, against which shales and two coal seams abut, 

 which were formed in the valley around the hill. The Handworth 

 Sandstone, southeast from Sheffield, occupies a valley eroded in the 

 underlying shales, but is conformable to the overlying measures. 

 The great red sandstone of Rotherham is unconformable to the un- 

 derlying measures, occupying a broad valley cut in them. Coal 

 seams are troubled by " rock faults " of one sort or another. The 

 Old Hards Coal is wanting in some collieries, having been replaced 

 with a deposit containing pebbles and water worn bowlders. The 

 Haigh Moor Coal, one of the most important seams, is injured so 

 badly by rock filling the lines of old watercourses, that in one district 

 it is practically worthless. The " faults " are from 8 to 70 feet 

 across and have northwest-southeast direction. At times they are 

 irregular, there being broad bands of sandstone, connected by nar- 

 row strips, which suggest a series of ponds.^°® 



The Silkstone Coal (Middleton Main) is troubled by "splits,'^ 

 which re-unite. KendalP^*' examined one at Whitwood, where the 



108 Green and Russell, pp. 185-192, 289-298. 

 103 Green and Russell, pp. 140. 281, 343-345, 397, 482, 689. 

 110 P. F. Kendall, " On the splitting of Coal-Seams by Partings of Dirt," 

 Trans. Inst. Min. Eng., Vol. LIV., 1918, pp. 1-21. 



