3IAGNESIAN LIMESTONE. \m 



or rather, party-coloured strata, are not of the regular series of rocks, 

 but merely fill up intervals between th«m, occupying deep valleys 

 and extensive plains ; in that case, such strata would bear some ana- 

 logy to the alluvial beds, and form a kind of link, to connect these 

 beds with the regular strata of the hills. — It is observable, that we 

 have not found in these party-coloured beds any appearance of organic 

 remains ; though such remains occur in the strata on both sides. 



The Magnesian Limestone of the county of Durham (q) is 

 without the bounds of our district ; yet, as it succeeds our red strata, 

 we may briefly notice it. This limestone, commencing at Hartlepool, 

 occupies the Durham shore, with a few interruptions, to within a mile 

 or two of South Shields, Avhere it leaves off abruptly, its northern 

 termination appearing like a steep wall, but of no great height. From 

 thence, its limits in the interior are traced in a south-westerly direc- 

 tion, by Bolden, Painshaw, Sherburn, Ferryhill, &c.; passing along 

 the skirts of the coal district, and arriving at the Tees below Winston 

 bridge, about ten miles above Croft bridge. The limestone that 

 passes behind our district, by Ripon, Knaresborough, Tadcaster, 

 Brotherton, and Knottingley ; and that stretches to the south by 

 Doncaster, as far as to Nottingham ; is understood to be the conti- 

 nuation of the same rock ; but we do not know that its continuity 

 has been distinctly ascertained. 



Numerous and interesting are the forms which this limestone 

 assumes. Some of the most singular varieties occur near Sunderland. 

 Of these we have already had occasion to mention the botryoidal or 

 pisiform variety, which is a kind of oolite on a large scale, composed 

 of clusters of crystalline globules. Another variety, no less remark- 

 able, occurs in some rocks to the north of Whitburn. It contains 

 numerous radiated crystalline cones, with their apices downwards, 

 the radiations of which are so arrainged, that when their bases are 



2 V 



