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592 ADDITIONAL NOTES.

falt, or muriate of foda, and vitriolated magnefia, commonly called Epfom falt, which in the fea-waters furrounding this ifland were found at a medium to exift in the proportion of one thirtieth part of common falt, and one eightieth part of vitriolated magnefia compared to the quantity of water. And fecondly as thefe falts are believed by many philofophers to have been formed by vegetable and animal matters, which principally grew upon the furface of-the dry land, after it was raifed out of the primeval ocean; and that in confe-

“quence the faltnefs of the fea was poñterior to the formation of the

primeval rocks of limeftone; and from hence we underftand, why

* thofe limeftone ftrata, which have not been diflolved or wafhed

in fea-water fiñce the fea became falt, are not mixed with mag- nefia.

The chalk muft have been diflolved and precipitated from water, as it exa@ly refembles the internal part of fome calcareous ftalactites, which I have in my poffeflion; yet there is no appearance of its component particles having been rubbed together mto fmall globules, and may not therefore have been removed from the fituation, where it was produced, except by its elevation above the furface of the ocean.|

But that alluvial limeftone, which confifts of fmall globules adher- ing together, called Ketton limeftone, and of which there appears to be a bed ten miles broad from Beckingham to Sleaford in Lincoln- fhire, and twenty miles long from Sleaford to Lincoln, I fufpect may probably confift of magnefian limeftone; which is alfo faid in that country to do no fervice to vegetation; for this alluvial lime-

ftone by having evidently been long rolled together beneath the fea,

by which the fmall cryftallifed parts of it have had their angles rub- bed off, is moft likely to have thus been mixed with the magnefa of the fea-water, which is faid to contain one eightieth part of its

weight of vitriolated magnefña, as above mentioned, At the lime-works at Ticknal near Derby there appears a ftratum of