351 
1909-10.] The Glenboig Fireclay. 
Grit. Above the fireclay there is a series of sandstones, above which there 
is often a thin coal seam ; above this seam is a band of dark shales in 
which Mr Tate discovered marine fossils. The exact sequence of beds is 
shown in the following record of a recent bore : — 
Made ground 
Broken whin [quartz diabase] 
Soft broken clay . 
Hard ironstone rib 
Broken clay .... 
Broken sandstone 
Dark shale .... 
Ironstone rib 
Sandy shale .... 
Coarse sandstone . 
Shale ..... 
White sandstone . 
Coarse sandy shale 
Shale with plies of coal 
Ironstone .... 
Dark sandy shale . 
White „ ... 
Dark „ ... 
Compound .... 
Fireclay .... 
Dark variegated shale . 
Hard white sandstone . 
Dark shale .... 
Roman Cement 
Fm. ft. in. 
0 4 0 
0 3 6 
0 4 6 
0 0 4 
0 10 
5 2 0 
0 2 6 
0 0 2 
0 2 0 
0 0 8 
0 10 
14 3 
2 0 0 
0 5 10 
0 0 3 
14 9 
0 4 0 
0 2 6 
10 2 
1 0 4 
0 3 0 
0 1 6 
0 2 0 
0 0 10 
19 3 1 
Examination in the mine gives no definite evidence as to the method 
of formation of this fireclay. It is usually jointed into small irregular 
angular lumps, the surfaces of which are abundantly slick ensided, as in 
most thin seams of homogeneous clay which have undergone much con- 
traction, and as is common in most English fireclay.* Bedding is only 
obscurely indicated in the mass, but is often clearly shown in microscopic 
sections. The character of the bedding indicates that the clay was deposited 
slowly in quiet water, and that the original arrangement of the particles 
in the middle of the clay lumps has not been disturbed ; for flakes of quartz 
* See, e.g., A. H. Green, op. cit., p. 19. 
