266 J. W. Jackson — Foramlniferal Limestone. 



It was a wet, stiff clay, of dark-gray colour. On heating to 120° C. 



it lost 20*1 per cent., and there was a further loss of 6-3 per cent. 



on ignition. 



The residue was of brick-red colour, and on analysis gave the 



following results : — 



Silica 67-9 



Alumina ... ... ... ... 18'3 



Ferric Oxide 8-7 



Lime 1-3 



Magnesia ... ... ... ... 1-2 



Potash 1-6 



Soda 1-4 



100-4 



VIII. — Mottled FoK.ijiiNiFERous Limestone in West and North 



Lancashire. 

 By J, Wilfrid Jackson (Manchester Museum). 



EARLY in 1904, whilst .spending a holiday at Silverdale, near 

 Garnforth, I noticed at the roadside near the Silverdale Hotel 

 several heaps of a peculiar mottled limestone which was being broken 

 up for road-metal. The resemblance to specimens I had seen from 

 Derbyshire struck me at once, and I was not long in locating the 

 quarry from which the material had been derived. The exposure of 

 the rock is situated near the turn of an old cart track leading from 

 Silverdale Green to Burton Well. When I visited the place there 

 was a section visible of about 12 to 14 feet long and 2 to 3 feet deep. 

 On the top was a thin layer of surface soil with vegetation on it. The 

 floor of the quarry was also of the same mottled limestone. The strata 

 here and in the immediate neighbourhood are rolling with a general 

 dip of 10° E. 



Whilst traversing the district again in 1905 I came across another 

 small exposure of this mottled limestone in a small roadside quarry 

 near Woodwell, about three-quarters of a mile south-west of that at 

 Burton Well. Here about the same depth was exposed, the strata 

 dipping slightly to the S.E. I cannot say definitely, as yet, whether 

 the.se two sections are exposures of the same bed, but it is highly 

 probable. 



Quite recently I came across a small slab of mottled limestone at 

 the Chadwick Museum, Bolton, which the curator, Mr. T. Midgley, 

 informed me had been obtained from Grange-over-Sands by a Mr. H. 

 Wright. It is part of a large slab found under some feet of Boulder- 

 clay on the Eden Park Estate, and both pieces are beautifully glaciated. 

 The direction of the scratches as the block lay undisturbed was noticed 

 to be from north to south. I also possess a .specimen and slides of 

 mottled limestone from the Boulder-clay near Burscough Bridge, South 

 Lancashire, collected by a friend of mine, which is highly foramini- 

 ferous, and agrees closely with the Silverdale specimens. 



The Silverdale specimens partake of exactly the same character as 

 those described by Messrs. Barnes and Holroyd from Derbyshire.' 



' " Ou the Mottled Carboniferous Limestone of Derbyishire " : Trans. Manch. 

 Geol. Soc, vol. xxvi, p. 561. 



