68 SECTIONAL ADDRESSES. 



channels cut to the depth of 90 feet in a deposit which must at the 

 tiuie of its deposition have approximated to sea level. 



So far we have been examining irregularities of the seam which are 

 clearly connected with the erosive effects of running water. But the 

 majority of the irregularities have not this simple character, and are of 

 a nature quite distinct from the consequences of erosion. 



The most common ahnormality is the occurrence of belts or patches 

 of ' proud coal ' in which the seam swells up to twice or thrice its 

 normal thickness — sometimes, though not always, by repetition of the 

 whole seam or of the upper part, either by shearing or by overfolding. 

 Hull long ago proposed to explain ' proud coal ' as the effect of the 

 stony infilling of the wash acting as a wedge of incompressible 

 material forcing out the coal-substance from beneath its margins. I 

 have observed effects attributable to the apposition of coal to sandstone, 

 but they were not of the kind in question. 



I have examined, underground, wash-outs in eight different seams, 

 some in only one colliery, others in eight or ten. In many instances the 

 seam which' has been interrupted lies between two seams that have by 

 extensive workings been proved to be entirely unaffected by such dis- 

 turbances. I have on several occasions passed entirely across the site 

 of a ' wash-out ' in the workings of seams lying either above or below, 

 thus demonstrating that the phenomena are confined to a single seam 

 and the strata immediately adjacent to it; usually the seat-earth itself 

 is unmoved. 



It has been suggested that all the violent displacement and over- 

 ridings are brought about by tectonic agency, and that they are thrust- 

 planes. The localisation to a single stratigraphical plane should suffice to 

 discredit this explanation, but it is still more definitely refuted by the 

 fact that, in reply to questions put to every colliery manager I en- 

 counter, I have heard of only three examples of faults of the reversed 

 or overlap type in the whole coalfield, two of which accomplished a dis- 

 placement of only 3 or 4 feet. An amplification of the same explanation 

 ascribes the displacements to a thrust with a movement from S.E. to 

 N.W. and a common cause to the cleat or cleavage of the coal which 

 is normally directed to the N.W. It suffices to refute this to remark 

 that the wash-outs I have explored in this coalfield are aligned in four 

 principal directions, so that if superposed they would give what may 

 be called the Union Jack pattern, i.e. N.E.— S.W., N.W.— S.E., 

 N.— S., andE.— W. 



Moreover, if these so-called ' wash-outs ' are not due to the erosive 

 effects of contemporaneous or sub-contemporaneous streams, but to 

 flat hading faults, any coal displaced should be presently found again 

 without any loss whatever. That swellings and duplications of the 

 seam occur we have already noticed, and such phenomena have been 

 pointed to as evidence that there is ' no loss ' of coal in connection with 

 the so-called wash-outs. But losses a.nd the gains by duplication do 

 not, in fact, balance. A simple and convincing case is a wash-out 

 in a thin seam of coal only 1 ft. 9 in. in thickness at Mirfield, in which, 

 by taking measurements of the thickness of coal present and the breadth 

 of the barren area, I have been able to show that a gap with no coal 



