Prof. Percy F. Kendall — On 'Cleat' in Coal-seams. 51 



The Southowram set of readings (one of several in the same colliery) 

 is interesting, as showing that actually the jointing in the very roof 

 of the seam is as divergent from the cleat as it is possible to bo. 

 A better case is, however, afforded by Robin Hood Quarry, midway 

 betwixt Leeds and Wakefield. At tliis place a great pit has been 

 excavated in the Middle Coal-measures for the extraction of shale for 

 brick-making, and, as it is on the site of an old shallow coal-mine, 

 not only was the shaft opened out, but many of the old roads in the 

 famous Haigh Moor Seam, with their primitive oaken timbering, are 

 now laid open to the day. The seam itself, roughly 3 ft. 6 in. in 

 thickness, has been bared over a considerable area, and the unusual 

 experience is afforded of studying one of the principal and quite the 

 most interesting seams in this coal-field in open sections and plan. 

 The surface of the seam shows very perfectly the direction of the 

 cleat, and in the accompanying Plate III, from a photograph by Mr. A. 

 Gilligan, the disposition of this structure and its relation to the dip 

 of the seam and to the jointing of the measures are shown in a very 

 instructive and convincing manner. The top 'lift' of the seam has 

 been removed over a space in tlie foreground, and the recent rains 

 have formed a pool of water, the general direction of the margin of 

 which defines the strike ; the rail placed perpendicularlj' to this 

 gives the dip. The further side of the pool is a hewn edge of the 

 coal, bearing no specific relation to the structure. 



The coal-seam shows the two sets of joints known to the Yorkshire 

 miner as the ' bord ' and 'end'. There appear to be differences 

 between local usages in the application of these terms, but a clear 

 account of the custom in Yorkshire, as well as of the way in which 

 the cleat affects the laying out of a collierv, will be found in a paper 

 by Sir William E. Garforth.' 



The ' bord ' in this seam is formed by a very strongly marked and 

 persistent system of joints, in the picture seen running along the 

 right-hand margin of the pool and almost directly away from the 

 observer. The faces are very smooth and lustrous, and are perpendicular 

 to the bedding ; they are in general parallelism, with very little 

 convergence. In the most superficial layer of the seam the intervals 

 are very small, not more than three-quarters of an inch. In the next 

 layer the unjointed intervals are 2 inches in breadth, and in the massive 

 seam below they are still larger. It may be said in general terms 

 that the interval is roughly proportional to the thickness. 



The ' end ' is much less regular, and the direction varies from one 

 pair of ' bord ' joints to the next, so that the seam breaks with 

 a ragged ' end'. These differences determine in a large number of 

 cases the mode of laying out of a colliery : in the present instance 

 the roads are bounded by ' bord ' faces. 



The surface of the seam is marked in some places by the imprint of 

 large trees, and I observed one stigmarian impression. The imprints 

 that I noticed were laid out about E. 10° N. 



The beds resting immediately upon the seam are very argillaceous 

 shales with many ironstone nodules with plant-remains, and they are 



^ Trans. Manchester Geol. and Min. Soc, vol. xxviii, p. 203, 1903. 



