The BRAZILIAN STONE. 91 



Were I to form a conjecture in relation to the natural hi- 

 ftory of this flexible Brazilian flone, I would fuppofe, that it 

 had been originally, like many fimilar ftrata, attendant upon 

 the Alpine limefhones, confolidated with calcareous fpar ; and 

 that the confblidating fubftance had been afterwards diflblved 

 out, as it always is in ftones fufficicntly expofed to the in- 

 fluences of the atmofphere. This fuppolition is alfo countenanced 

 by the report, which I have received, with regard to the fitua- 

 tion in which this folitary flone was found. It is faid to 

 have been in the foil or upon the furface of the earth. But 

 without allowing ourfelvrs to be led into any hypothetical fpe- 

 culations upon the fubjecl:, we may now reafon from what ap- 

 pears more evident in the conftruc"tion of this mineral. 



Nothing is more common in our north Alpine country, as 

 well as in every other extenfive country of the fame kind, than 

 ftrata of granular quartz and mica ; and in our low country, 

 we have many micaceous fand-ftones ; yet flones of that kind, 

 with palpable flexibility, have not been obferved. Therefore 

 we have reafon to believe, that it requires many conditions, 

 feldom to be found together, in order to produce that flexibi- 

 lity which is fo remarkable in this Brazilian flone. It is not 

 enough to be compofed of filiceous particles and plates of mica ', 

 thefe muft be duly proportioned and properly arranged. But 

 when all the materials fhall be juftly proportioned and perfect- 

 ly arranged, perhaps the moft difficult part is ftill to come ; 

 that is, the giving a proper union to the parts, fo as to 

 form a cohering flone, at the fame time that the proper fepara- 

 tion among thofe parts is fo preferved as to allow them to move 

 in relation to each other. Were all the particles united or ce- 

 mented where they are in contact, it is plain that the flexibility 

 of this flone would be loft; and were there no union among 

 the component particles'; it would ceafe to be a flone ; a term 

 which implies a certain degree of confiftency or ftrcngth. But 

 between thofe two extremes, there are not only many degrees, 



M 2. but 



