1897.] NEW YORK ACADEMY OF SCIENCES. 229 



Mountain Mine and the Gannister seam have been largely 

 worked by adits and shafts to supply the wants of the numerous 

 cotton manufacturing towns of Lancashire and are still largely 

 used. The chief coal supply from the Lower Coal Measures 

 will, in the future, have to be drawn from a five-feet seam formed 

 by a union of the Gannister and Upper Foot seams, which takes 

 place along an irregular northwest and southeast line, a little to 

 the north of the Rossendale anticlinal. Although up to the 

 point of union the individual thicknesses of the two mines are 

 but two feet six inches, and eight inches respectivel}', 3'et at 

 their junction the united seams swell out to a thickness of nearly 

 8 feet, and the average over a great area is five feet. 



The special features of the union of these two seams were 

 dealt with by J. Aitken, F. G. S., in a paper read before the 

 Manchester Geological Society (See Trans., Vol. V.) and his ex- 

 planation is probabl}^ the correct one; viz.: That a part of the 

 Gannister area was one of subsidence, the submersion going on 

 until a sufficient depth beneath water was obtained to allow of 

 the deposition of sufficient detritus to form the rock mass over- 

 lying that mine and separating it from the thin coal above. He 

 goes on to say in his paper, " it would further appear that the 

 surface over which the five feet coal was then in process of for- 

 mation remained stationary and undisturbed, and that the oper- 

 ations or nature were not in any way interrupted." 



This view is supported by the fact that the coal of the Five 

 Feet Mine is considerably thicker than the aggregate of the two 

 mines while separate, the growth of vegetation over the area be- 

 ing evidently continuous during the period in which the sub- 

 merged portion was being silted up. When the latter had taken 

 place the coal forest grew out over the shallows, giving rise to 

 the thin " Upper Foot " coal, alter which the whole area occu- 

 pied by the Five Feet Mine and the Upper Foot coals was sub- 

 merged, and a uniform deposit of mud took place. 



The coals are all bituminous and caking. Iron pyrites occur 

 as nodules in some of the coals, and also as a thin film upon 

 joint planes, in some cases (the upper seams) so abundantly as 

 to seriously injure the usefulness of the coal. The demand for 

 these coals is entirely local, and their use as fuel is restricted 

 to engine boilers and the open fireplaces of the people. All the 

 seat-earths or fireclays are much used in the manufacture of 

 firebricks, gas retorts, chimney pots and drain pipes. 



The associated flagstones and massive bedded sandstones are 

 quarried to a large extent for building purposes. The houses in 

 many of the smaller towns are nearly all built of sandstone, 

 bricks being used chiefly for inner walls. 



