:u:OOEE ABX0E3IAL SECOXDAET DEPOSITS. 491 



Ostrea fimhriata, Moore, is especially plentiful, and affords fine 

 examples. As the shell is nearly always attached to the upper 

 surface of the conglomerates, it is evident that the beds in this 

 quarry have been accumulated at intervals, and less rapidly than 

 might be supposed with a series of conglomerates. It is matter of 

 regret that the thin laminated marls, Xo. 12, have not yielded any 

 fossils, as they appear so suited for the preservation of any delicate 

 organisms, such as Estlieria, Plants, or Insects. The stone, Xo. 14, 

 only occupies the lower corner of the section, and is lithologically so 

 like the "\\Tiite Lias in its fi-acture, and the stratigraphical position 

 in which it should be found above the Avkula-contorta beds, that I 

 cannot help referring it to that horizon, though it is unknown 

 for some miles. The Rhcetic beds have no superficial development in 

 a northerly direction beyond, but pass at once under Inferior Oolite, 

 which is seen in the Hapsford road, and which, in the Iladstock rail- 

 way, attains an exposed thickness of 30 feet. At its base in this 

 district this formation is at times highly siliceous and conglomeratic. 



5. Gurney Slade Liassic Dykes. — My previous observations have 

 had reference to the entire south-eastern breadth of the Mendip Car- 

 boniferous Limestone. That the Liassic infiUings pass completely 

 through the Mendips from east to west there cannot be a doubt, as 

 they are to be recognized at points widely asunder. They occur 

 again at Gurney Slade, about nine miles from the sections I have 

 just been describing. At this place there is a large quarry on the 

 right of the roadway leading from Old Down to Gurney Slade, where, 

 in the middle of the Carboniferous Limestone, the quarrymen have 

 left a large Liassic dyke standing up like a wall, and dividing the 

 quarry into two parts. It is about 4 feet broad by 12 in height, and 

 is, Hke those of Holwell, made up of vertical bands of stone, often in- 

 termingled with veins or pockets of excellent haematite iron-ore, and 

 presentmg all the attendant characteristics of a mineral vein. An 

 examination of the sides of the deposit, particularly on the northern 

 side, reveals the presence of a number of Pentacrinites, EliyncJioneUa 

 vadahilis, and other Liassic fossils. 



Proceeding again another eight miles "west of Gurney Slade, the 

 same phenomena are present in the midst of the old Eoman lead- 

 workings of Charter House, and on the most elevated tableland of 

 the Mendips. 



6. Charter House Liassic Lead Mine. — The mineral districts com- 

 prised in this part of the Mendips and Priddy were extensively 

 worked during the Eoman occupation ; and the great industry they 

 manifested is shown by the enormous quantity of refuse slags and 

 slimes left by them in some of its vaUeys. Owing to their imperfect 

 mode of working, about 12| per cent, of lead remains, which is now 

 being extracted by several companies. In general, the lead-ores of 

 the district '• prove " near the siu-face ; and so well and completely 

 did the Romans appear to have exhausted the veins, that little has 

 subsequently been worked profitably. I paid a visit to a shaft 

 M'hich had been sunk as an experiment by one of the companies, but 

 which had lately ceased working, at Charter House Warren. It is 



