for "Manufa&uring Cajl Iron. 25 



coal : little extra labour is therefore requifite to bring dowa 

 the ftone ; and the double purpofe of obtaining both mate- 

 rials is thus advantageoufly anfwered. 



When ironftone in bands accompanies limeftone: it is 

 moft commonly of an inferior quality. Its component parts 

 are chiefly calcareous, and the quantity of iron it contains is 

 fmall. Ball ironrtones found near to lime are of a much fu- 

 perior quality, and for the moft part contain a confiderable 

 proportion of iron. 



Thus ftratified in the vicinity of lime, many ironftones are 

 found with various impreflions of marine remains ; and not 

 ^infrequently compact and entire fhells, univalve and bivalve, 

 are found in the heart of the band. It is however ftill more 

 difficult to conceive how fhells could be depofited, diftant 

 from lime, imbedded in ironftone, incumbent on coal, at the 

 great depth of 80 yards from the furface. In our neigh- 

 bourhood, at this depth, a fmall band of ironftone is found 

 completely covered and interfperfed with diftincl mufcles of 

 an ordinary fize. 



Among the great variety of rich ironftones found in Lan-, 

 cafhire, the Rottenburn ftone challenges particular attention, 

 for the beautiful fpecimens it affords of vegetable decompo- 

 fition and impreffion. This ftone confifts of a band and an. 

 accompanying ball. The former abounds with fine fpeci- 

 mens of the ramification of trees, fhrubs, &c. In the procefs 

 of decay, and the fubftitution of mineral in place of vegetable 

 fubftance, the more ligneous parts and the bark are diftinctly 

 preferred from the heart of the flioot. The former are found 

 of a proper thicknefs, confiding of pure calcareous earth, 

 encircling the central parts, which commonly have been 

 difplaccd and occupied by the fame compound as the general 

 mafs. As the extenyl parts of the vegetable feem to have 

 been laterally formed, it is prefumed that they have withftood 

 the decomposition of the foftcr parts, and have only been 

 difplaced afterwards by a filter which has contained calca- 

 reous earth in folution. This iron-ftone contains 371b. 



in 



