^J Northumberland and Durham. 87 



with such inquiries may find it difficult to conceive how tliis 

 measuremeiit was effected. I shall therefore add an explanatory 

 sketch, which will, I trust, make the subject intelligible. By 

 extending the line east and west beyond Mr. Forster's line of 

 section, it will cross the whole island in that parallel of latitude, 

 priesenting a section of England which I believe will convey a to- 

 lerably correct idea of the geological arrangement of tiie rocks 

 and strata horn the German ocean to the Irish sea. The ge- 

 neral dip of the strata on the eastern side of the island, as before 

 stated, is to the south-east : and of course each stratum rises to 

 the surface in the south-west, when not cut off by a fault. 



The line LL is supposed to represent the level of the sea from 

 which the beds of magnesian limestone rise on the east marked 

 A. The coal formation commences at B, rising from under the 

 inagnesian stone. A perforation at 1 will measure the thickness 

 <>f all the strata to the bed of coal marked a. By proceeding 

 further west, the bed a rises near tiie surface at station 2, vv-hei-e 

 another pit may be supposed to sink to stratum h. The depth 

 of this added to the former will give the thickness of the whole 

 sti-atafrom B to stratum h 2. Proceeding in a similar manner at 

 station 3, we oijtain the thickness of all the strata as far as C and C, 

 on the west of the mountain at C. Here tlie strata making their 

 appearance may be measured on the surface, due allowance being 

 liiade for the angle of inclination. The section of Mr. F. be- 

 gins west of the magnesian limestone. The first bed is the clay 

 and soil on the surface, under which is a bed of hard siliceous 

 sandstone called provincially post, and at the depth of seventeen 

 fathoms the hrst thin seam of coal, under which the various 

 strata of slate clay or shale. Bituminous shale and variously 

 coloured sandstones succeed each other ; the most remarkable of 

 which are designated by their provincial names, and those of 

 njinor importance by the letters n or s, to denote that they are 

 principally argillaceous or siliceous. An Inspection of the 

 plate will render any further explanation unnecessary, besides 

 tiiat of the provincial names which are given below. 



More than thirty beds or seams of coal succeed each other, which 

 arc sufficiently well marked to be distinguished in different situ- 

 ations where they occur ; each bed of coal generally preserving its 

 own strata above and below it in its whole extent. It may be 

 observed tliat all the principal coal beds are comprised within 

 200 fathoms, or 400 yards, from the beginning of the section. 

 Though some few beds occur in the lower strata, they are of 

 inferior quality and generally not workable. In a similar man- 

 ner in the Yorkshire and Derbvshlre coal fields, there are a few 

 thin seams of coal in the great mass of sandstone and shale which 

 lie under the principal coal beds, between tlicm and the metal- 



F 4 lifcrous 



