Subjacent to the Boulder-clay. 



243 



Fig. 3. Supposed general arrangement of Pocket, containing sand and clay in 

 Mountain Limestone, Bwlch Farm, near Nannerch, Flintshire. 



A. and B. Surface soil and drift, c. White sand interstratifled with grey buff and black sand 

 and thin layers of tough pipe clay. d. Mountain Limestone. 



the pocket consist of stratified white, black, grey, and variegated 

 sands containing carbonaceous particles, also a layer about a 

 foot thick of soot-like carbonaceous matter, and strata of dark grey 

 laminated clays, and nearly white pipe clay : the contents of this 

 pocket being but partially exposed, it is not easy to make out their 

 general arrangement ; in places they are very unconformable, per-, 

 fectly horizontal sand beds terminating abruptly against almost ver- 

 tical strata of tough plastic clay, and in another place a little pouch 

 of level layers of sand lies in the midst of similar beds very much 

 inclined. I have endeavoured to represent the arrangement in 

 Fig 1. The great variety of gradual shiftings and slippings, which 

 the contents of this singular cavity appear to have undergone, have 

 produced a complexity of arrangement not easy to explain. 



The section represented in Figs. 2 and 3, occurs at a height of 

 about 850 feet above the sea on Bwlch Farm, between Nannerch 

 and Longrake Mine, one mile to the south-west of the example just 

 described. Tig. 2 represents in detail the portion actually ex- 

 posed, and Fig. 3 what is most probably the general arrangement 

 of the beds in the limestone cavity. The limestone is not visible 

 in immediate contact with the sand ; but as the sand and clay has 

 been sunk through forty feet, and the limestone appears within a 

 short distance on all sides, they must occupy a complete "Pocket." 

 similar to those near Llandudno. The individual strata in this 

 section quickly alternate, and are very thin, consisting of quite 

 white, grey, yellow, and black sands, separated by layers of tough 

 white clay, very regular and continuous, but not more than two or 

 three inches thick. 



The darker beds of sand and clay contain a great deal of car- 

 bonaceous matter, and here and there, in contact with the clay-beds. 



