EE

ADDITIONAL NOTES. sg

no advantage, and even injurious to land: which has probably been owing to their having ufed the magnefian lime, and having laid on too much ofit. a

Mr. Tennant firft found maonefan lime near the town of Don- cafter, and afterwards at York, at Matlock in Derbyfhire, and at Breeden in Leicefterfhire, and at Workfop in Nottinghamfhire. He obferves, that the cathedral and walls of York are built with this magnefan limeftone; and that at Matlock the magnefian and cal- careous limeftones are contiguous to each other; the rocks on the fide of the river Derwent, where the houfes are built, being magnefan, and on the other fide calcareous. He obferved alfo here, that the magnefian limeftone was incumbent on the calcareous: for in des {cending into a cave formed in that rock, he found a feparate vein of calcareous limeftone, which was full of fhells, but contained no mag- nefia; and obferves in general, that magnefian limeftone may be rear dily diftinguifhed from the calcareous by its fo much flower folution in acids, and that it contains generally very few fhells, but that thofe alfo are impregnated with magnefa.

As all imeftone may be divided into three kinds; the rocks, which remain, where they were formed from fhells beneath the ocean, ex- cept that they were afterwards elevated by fubmarine fires; and fe- condly into alluvial limeftone, as thofe which have been diflolved in water, and fimply precipitated, as the beds of chalk, which contain only the moft infojuble remains of fea-animals, as the: teeth of fharks; and thirdly thofe which after having been diflolved and precipitated, have been long agitated beneath. the fea, till the par- ticles have been rolled fo againft each other, as to acauire a globular form, which is faid:to refemble the roe, or fpawn, of ffh, and which contain very few fhells or none, as the Ketton ftone, and that which L'have feen on Lincoln Heath extending almoft from Sleaford to Jancoln.

Now. as the falts of the fea confift of only two kinds,. common: {al ia Co: