Ironstone. 



244 YORKSIHRE ALUM WORKS. 



springs of very good water, some of them highly impreg- 

 nated with iron, united with carbonic acid gas; the acid be- 

 comes disengaged by exposure to the air, and a copious 

 precipitate of the iron, of -a diili red colour is deposited. 

 The temperature of several of these springs is from 44° to 

 46° Fah. uniformly throughout the year. 



Coal and jet. Under the sandstone is frequently found a seam of coal, 

 or jet, of an indifferent quality. Sometimes these occur 

 enclosed in the substance of the sandstone, but they rarely 

 exceed two inches in thickness, and are of no great extent. 



Q] The clay is chiefly alluvial, or derived from the decom- 



position or shale. The colour is generally of a bluish giay, 

 sometimes of a yellow ochrey colour. Tlie thickness of the 

 strata may be averaged at two feet. 



The ironstone is found in loose or broken strata, from 

 tw o to twelve feet thick ; the quality is much inferior to 

 those seams of iron ore found iri the aluminous schistus, no- 

 ticed hereafter. Its specific gravity is about 3*1. It may 

 / here be remarked, that the whole of the strata are traversed 

 by veins, intersecting each other at right angles, in a south- 

 erly and an easterly direction. The masses, both of the 

 schistus and sandstone, always appear in the form of solid 

 parallelograms, occasioned by the crossing of the veins, 

 the longest side of the solid lying between N. and S. I 

 have noticed, that, when the stratum of clay has been unco- 

 vered for a considerable time in the summer season, on the 

 abstraction of water from the clay it cracked in regular divi- 

 sions, of the same rectangular figure as those visible in the 

 sandstone and schistus. This observation on the regularity 

 of the divisions assumed by alumine in drying is noticed by 

 Chaptal (Chemistry applied to the Arts, vol II, p. 46). Per- 

 haps the formation of the basaltic pillars may have been 

 effected by this combination of fire and water in some gra- 

 dual manner. 



Of the Mineral and Fossil Bodies found in the Aluminous 

 Schistus. 



T. M •/.' J A very pure native alumine is found enclosed in a no- 

 Fossils found J '■ i,--, ,, c i • c 



in theschistus. dule of stone vesembhng indurated clay, beveral species ot 



ammonitce are found enclosed jn an argillaccQUS ironstone 



of 



