THE GEOLOGICAL STRUCTURE OF THE CANONBIE COALFIELD. 865 



A glance at the journal of the Forge bore shows that seven coal-seams were passed 

 through, ranging in thickness from seven inches to two feet, the lowest seam being 

 reached at a depth of 249 fathoms. 



The evidence obtained from these two bores demonstrates the existence of thin coal- 

 seams underneath the Carboniferous red sandstones of Canonbie. Though they cannot 

 be correlated with the known Canonbie coals, it is not improbable that they may belong- 

 to the upper part of the Byre Burn group, the whole sequence of which has not been 

 proved. 



In the sheet of vertical sections (Plate II.), illustrating diagrammatically the more 

 important bores put down in the Canonbie district, we have shown what we believe to 

 be the relative stratigraphical position of the strata in each bore in the Carboniferous 

 system. In our opinion, had the bores at the Forge or Rowanburn, within the area of 

 Carboniferous red sandstone, been sunk to a sufficient depth, they would have passed 

 through, in turn, the Middle Coal-measures of Byre Burn, the Lower Coal-measures of 

 Rowanburn, the Upper Limestones and Kilnholm coals in the Rowanburn bore, and 

 eventually the massive Lower Limestones shown in the Catsbit section.* 



III. Description of Horizontal Sections. 



1. Buchtknowe to Larriston Fells and Kershope Burn. — This line of section 

 illustrates the structure of the area in the northern part of sheet 11 one-inch map, 

 embracing portion of the Hermitage Water and Upper Liddisdale. It shows the 

 ascending sequence from the Upper Old Red Sandstone (c 3 ) resting on the Silurian floor 

 at Dinley Spout, through the Birrenswark volcanic zone (d 1 ) and the Whita sandstone 

 (d u ) to the Cementstone group (d jii ). On the west slope of Arnton Fell these sub- 

 divisions are faulted against the inlier of Upper Silurian strata on that ridge ; while on 

 its eastern side the sequence of the lower groups is again repeated in Upper Liddisdale ; 

 the higher part of the Cementstone group, with its marine limestones, being surmounted 

 by the Fell sandstones (d iv ) and the Lawston coals (d vi ) on the Larriston Fells. 



2. Arldeton Fell to Caerby Hill and Kershope Burn. — On the heights between the 

 Ewes Water and the basin of the Liddel (Arkleton Fell and Cloak Knowe), the sequence 

 from the Upper Old Red Sandstone to the Whita sandstone is exposed, the strata 

 being there pierced by several necks of volcanic agglomerate and massive igneous rocks. 

 Eastwards the members of the Cementstone group succeed, with which a sheet of basic 

 lava is associated on Bedda Hill, till near Sorbietrees, south of New Castleton, they are 

 overlaid by the Fell sandstones. On Caerby Hill these sandstones are capped by basic 

 lava, probably representing the volcanic zone of Glencartholm, followed in turn by the 

 Lawston Linn coals. 



* The lamellibranchs from the recks of the Canonbie coalfield have been examined by Dr Wheelton Hind, 

 who is of opinion that they confirm the evidence obtained from the plant-remains that the strata in which they occur 

 belong to the Coal-measures,— Summary of Progress, Geological Survey for 1902, p. 137. 



