154 W. M. Hutchings — Ash-slates of the Lake-Didrict. 



land the coal is sometimes directly overlaid by a limestone, and rests 

 with its accompanying underclay on a sandstone. We can scarcely 

 suppose an abrupt transition from terrestrial conditions to those 

 requisite for the formation of limestone ; or, in other words, that the 

 sinking area would not pass through the stage where sand and mud 

 would be deposited on the coal. And there is a further difficulty 

 in understanding how the terrestrial surface could be lowered to 

 the requisite stage for the formation of limestone without suffering 

 extensive denudation. A more probable supposition seems to be, 

 that the shallow, near-shore, conditions which allowed the formation 

 of a sandstone gave place gradually to the deeper water in which 

 underclay, coal, and limestone were formed in succession. 



Further examples of limestone directly overlying coal-seams 

 may be cited from the Carboniferous Limestone Series of Scotland. 

 Thus, Sir A. Geikie describes a limestone "of a compact bluish- 

 grey texture, with abundant fragments of small encrinites," resting 

 on " an eight or ten inch seam of coal " (Geology of Edinburgh, 

 Surv. Mem. 32 Scotland, p. 48). 



Again, a section given on p. 55 of the same Memoir shows a 



2 feet seam of coal overlaid by 8 feet of limestone and resting on 



3 feet of " Cement " — a kind of impure ferruginous limestone. It is 

 interesting to note that the upper 8 inches of this coal is "Parrot" 

 or cannel coal. 



On p. 81 of the same Memoir Mr. Howell describes an exceedingly 

 interesting case in which a coal-seam with its fire-clay occui's between 

 two beds of limestone. The seam is not continuous, and the two 

 beds of limestone sometimes come together. 



Such a case would be extremely difficult to explain satisfactorily 

 on the growth in situ hypothesis, and it is not easy to resist the 

 conviction that if the limestone was formed in inoderately deep 

 water, and some little distance from land, coal and fire-clay were 

 also formed under approximately similar conditions of depth and 

 distance from shore. 



On the whole, therj, it must be admitted that the occurrence of 

 such fragmentary drift coal as we have been considering furnishes 

 a strong argument that seams of ordinary coal may, in certain cases, 

 have had a similar oriy-in. 



V. — Notes on the Ash-Slates and other Eooks of the Lake 



District. 

 By W. Maynard Hutchings, Esq. 



WHILST studying the sedimentary roofing-slates of North Wales 

 and Cornwall, and allied materials, my attention was also 

 directed to those most interesting rocks, the ash-slates of the Lake 

 District, often externally so closely resembling some of the Welsh 

 and Cornish examples, though differing so much in origin. In 

 course of time I have collected, and had sections prepared from, 

 a considerable number of specimens from many quarries and other 

 jilaces at various parts of the district, both very fine-grained well- 

 cleaved actual roofing-slates and also the attendant coarser beds. 



