OBSERVATIONS ON BASALT, &C. 123 



the fra&ures will be at leaft as frequently acrofs the natural 

 joints as in their direction, yet, even by this rude method, 



fome perfect molecules may be difiengaged ; for we find, that 

 water pafling over large fur faces of filiceous fand, finds fome 



molecules of filex in the ftate proper for aggregation, and even 



for cryftallization. Mechanical fufpenfion in a fluid medium, 



of fuch denfity that the cryftalline polarity may be enabled 



to counteract the power of gravity, is with juftice confidered 



by Mr. Smithfon the only requifite for the formation of cryftals. * 



The circumftances I have detailed, appear to me an additional 



confirmation of this remark, and perhaps go ftill farther, by 



fliowing that even the fluidity (in the common fenfe of the J ven flu '!? it >' 

 . / v , \ does not feem 



word) of the fufpending medium is not an indifpenfable con- an indifpenfabk 



dition. For it appears impoffible to annex the idea of fluidity condition. 

 to the union of the minute globules which form the jafpideous 

 fubftance, ftill lefs to that fubftance when formed, and dill 

 lefs to thofe fpheroids whofe obftinate impenetrability is fo 

 ftrongly defined. And if, by any power of imagination, 

 thefe can be fuppofed to be fluid at the time they retain this 

 conformation, how can it be fuppofed that the compact hard 

 tenacious ftone into which they are changed could retain 

 thefe characters in a fluid ftate? Yet the fubfequent formation 

 of cryftals proves, that either all thefe contradictions muft be, 

 or that the particles of bodies apparently tblid muft be ca- 

 pable of fome internal motion, enabling them to arrange them- 

 felves according to polarity, while they are folid and fixed, 

 as far as they have reference to the ordinary characters of 

 fluidity. 



Inftances even more remarkable have very long been known Inftances of the 

 and authenticated, though perhaps they have not been generally andTrranee-' 01 " 

 regarded with the attention then deferve. Glafs veflels are ments of par- 

 well kfiown to be convertible into Reaumur's porcelain, by the *' bodies 



r J at temperatures 



internal arrangement of their particles, without lofing their below fufion. 



external form, and confequently at a temperature very much 

 below that requifite for their fuiion, The change of glafs into Reaumur's por- 

 Reauinur's porcelain, does not arife from an evaporation of fcribed " ^ 

 the alkali, as has been alledged, but from a regular arrange- 



* See a chemical Analyfis of fome Calamines, by James Smith- 

 fon, Efq. Philofophical Tranfa&ions for 1803, page 27. See a!fo 

 Dolomieu, Journal des Mines, No. 22, page 53. 



• ment 



