G. W. Bulman — On Underclays. 359 



And from this to an ordinary Coal-seam with " partings " of 

 iinderclay, as in the following section of the Beeston Bed Coal, 

 is but a step : 



FT. IN. 



Coal 2 



Underclay ... ... ... ... ... 3 



Coal 1 3 



Underclay ... 5 



Coal 5 



Underclay 1 6 



Coal 6 



Underclay ... ... ... ... ... 2 



Coal 2 



Underclay ... ... ... ... ... 7 



Coal 2 



Underclay ... 2 



Coal 1 ^ 



(Survey Memoir. Yorkshire Coal-field, p. 192). 



Are we to look upon each "pai'ting" of underclay as a separate 

 soil and the foundation of a distinct marsh ? And if so, ought we 

 not also to consider all ordinary " partings " of a shaly, slaty, or 

 clayey nature? It is a little difficult to understand, granting the 

 formation of the underclay, how a stratum of clay two or three 

 inches thick, could support the large trees which formed the greater 

 part of the Carboniferous forests ; and the earth movements required 

 in the case of the above seam, supposing the underclay to be formed 

 in shallow water and the coal on land, would be as follows : 



After the formation of the lower 1 ft. 8|^ in. of coal, there must have 

 been a sinking of the land to the extent of two inches beyond the 

 thickness of the bed of vegetable matter. This must have been 

 followed by a pause of sufficient length to allow of the accumulation 

 of two inches of underclay in the shallow water and the growth 

 upon it of sufficient vegetable matter to form two inches of coal. 

 This must have been followed by a submergence of this coal to the 

 depth of seven inches, and a pause long enough for the deposition 

 of seven inches of underclay and the growth upon it of two inches 

 of coal. And so on to the top of the section. It is questionable 

 whether we are justified in calling in such a system of earth- 

 movements. 



Finally it must be observed that a fine-grained deposit such as 

 underclay is what we should expect to find beneath the coal on 

 some such hypothesis of its drift origin as that of Mr. Goodchild 

 (GrEOLOGiCAL Magazine, July, 1889). For in a gradually sinking 

 area the zone of deposition of sandstone and shale would gradually 

 give place to that of clay and vegetable matter. Again, the want of 

 lamination, which is such a striking feature of underclays in general, 

 would be a probable consequence of deposition in deep, quiet water, 

 far from land, since the supply of fine sediment would remain so 

 long suspended that its settling down would be likely to be un- 

 interrupted and almost uniform. 



There are two ways in which lamination may be produced : 

 (1) By flat plates of mica, which settle down more slowly than 

 the sand and mud, but in the same zone of sedimentation, and 



