30 
Now, at the Bold Hall and Collins Green Collieries, situated about half- 
way between St. Helens and Warrington, a series of Upper Carboniferous 
strata are met with, not at all comparable to those found in this Sealand 
borehole ; this latter section being more nearly allied to the Farnworth bore- 
hole and the Manchester district, 
The thickness of these Upper Coal strata at Bold and Collins Green is 
about 1,200 feet, of which the uppermost portion very much resembles the 
measures found in a borehole at Sandycroft, situated about seven-eighths of 
a mile south-west of the Sealand borehole, and which I consider are on a 
lower geological horizon than this last. By adding the thickness of the 
measures proved at Sealand to those of Bold or Collins Green, we arrive at 
the sum of 1,700 feet as the thickness of the Upper unproductive series in 
this district ; an estimate I believe to be approximately correct. 
The section that can, as far as my knowledge extends, be best correlated 
with the Sealand borehole is that of the clay hole of the Abenbury Terra- 
cotta Works, at King’s Mills, near Wrexham; the similarity of the purple 
marls, the grey sandstones, and the purple micaceous sandstones is certainly 
remarkable, and I am disposed to place them on the same horizon. These 
strata were classed by Professor Hull with the Permians of Salopian type, 
and seem to be identical with the beds found at the summit of the Keele 
series, at the Newstead Boring near Trentham, in North Staffordshire, where 
the thicknesses of Upper Coalmeasure strata has been proved to be 1,946 
feet; a fact that corresponds very closely with the estimate formed by 
comparing the Sealand section with those of Sandycroft, Bold, and Collins 
Green. 
As the lower subdivision of the Bunter is here 800 feet, we get a total 
of 2,500 feet as the depth to the productive coalmeasures; but it does not 
follow that, in properly selected localities, a much less thickness of both 
formations may not obtain. 


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Louis, U.S.A. 
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