A. Stnihan — Coal under Neiv Red Sandstone. 437 



cult to select a base-line for this sub-division, though the bright- 

 coloured soft sands certainly belong to the Lower Mottled Sand- 

 stone. It is interesting to find here concretions of iron pyrites in 

 a similar position to those found at Collins Green. They differ 

 in shape, being twig-shaped instead of spherical, but resemble them 

 in consisting of sand cemented by iron pyrites. These concretions 

 probably owe their origin to the action of water carrying sulphides 

 in solution, rising from the Coal-measures, and meeting with the 

 peroxide of iron which forms the colouring matter of the Trias. 

 In both cases the rock containing them had lost its colour.^ 



The dark purple and green marls associated with limestone at 

 "Winwick and Farnworth, and the similar beds, but without lime- 

 stone, found at Parkside, accord with those which have been long 

 known in a railway cutting near Whiston. They are probably the 

 equivalents of the limestone series in the Upper Coal-measures of 

 Manchester, where they are associated with valuable seams of coal 

 and ironstone, and are known as the Ardwick Limestones. 



The limestone found in the Winwick bore-hole was of a dull red 

 colour and earthy texture, and showed a brecciated structure in parts, 

 consisting of small fragments of grey limestone imbedded in a red 

 earthy matrix. At Farnworth, beds of grey limestone also were 

 found. Both the marls, the red earthy and the grey limestones, 

 brecciated in parts, and the purple and green marls, may be found in 

 the railway cutting at Whiston, so similar in character that specimens 

 from this section and from the bore-holes cannot be distinguished. 

 In order to complete the comparison, I submitted specimens of the 

 Winwick Limestone, with fragments from Ardwick and Whiston, to 

 Mr. Siddall of Chester, for examination under the microscope. They 

 were all found by him to contain Microconchus carbonarius, thus 

 rendering the identification almost certain. The purple colour of 

 the marls at these localities is due to the infiltration of colouring 

 matter from the overlying Trias. It will be seen that at Bold Hall 

 this staining extended to a depth of 364 feet 9 inches, and at Collins 

 Green to 151 feet 11 inches in the Coal-measures. 



Up to the present time, nothing further is known of these Upper 

 Coal-measures in this district, as the borings, which were in search 

 of water, were stopped on entering them. There is no doubt that 

 they overlie the whole of the productive Middle Coal-measures of 

 Lancashire. The dip of these Coal-measures along the southern 

 margin of the Coal-field being generally to the south-east, and at a 

 steeper angle than the Trias, they are succeeded in this direction by 

 higher beds, which cropping out in the old denuded floor of Coal- 

 measures on which the Trias rests, never rise to the surface at all. 

 The limestone series at Ardwick is underlain at a distance of 600 

 feet by the Bradford and Clayton Coal Series, but of the beds inter- 

 vening between this Coal Series and the Middle Coal-measures 

 nothing is known, except that strata, of a thickness of 1678 feet, 

 exposed in the valley of the Irk, belong to this part of the series. 

 (Geol. Survey Memoir on Country around Oldham). There is 

 reason to believe that this great mass of unproductive measures 

 1 The iron bavins: senrreffatecl out. 



