32 



extent, viz., from Sweethouse, its north outcrop, to Robins' Wood 

 House, where its southern boundary is covered by the overlying 

 Upper Coal Measures of the Coalpit Heath Basin, 



Fig. 1. — Section from Tortworth to Coalpit Heath. 



The Bristol Coal Field, extending as it does from Tortworth on 

 the north, to Vobster at the north foot of the Mendip Hills on 

 the south, may be conveniently divided into two sections, or a 

 northern and southern area, or the north and south coal hasins, 

 the natural or physical boundary separating the two occurring in 

 the neighbourhood of Kingswood, immediately north of Bristol. 

 I say physical division, because there is evidently a deeply-seated 

 east and west antichnal axis of disturbance along a line projected 

 from Bristol on the west, to the Wick Rocks and Drayton on the 

 east; it may be sKghtly north of this line, and through Kingswood 

 from Siston on the east, to Stapleton and Redland on the west, 

 and is probably a continuation of the axis of disturbance along 

 the line of great fracture from Clevedon, Clapton-in-Gordano, 

 the Observatory Down, Clifton, and on to Kingswood and Siston: 

 but be this line where it may, as far as its exact position is 

 concerned, it is evident that between these points, and deeply 

 seated, there does exist, either by fault or roll, (anticlinal,) a 

 disturbed line of sufficient magnitude to determine and give good 

 reasons for believing that the once continuous coal field may 

 now be divided physically and economically into two sections or 

 areas, viz. — a northern and southern. It is to the northern 

 half only that my remarks upon the Iron of the district will 

 apply, as the special localities under consideration are within 

 the area termed the "Northern Coal Field." This coal tract 

 north of Bristol is elliptical in form, and about eleven miles in 

 its longest axis from north to south, and the exposed portion from 

 east to west, or its transverse axis, is not more than four miles, 



