2i8 Ail-fcal Red Csjtjl. 



who for the fkft time bcIiolJs a fine group of tliefc cryftal.^ wUl naturally be dil^iofed to 

 aOc, What are the means employed by nature to produce this form ? Does tiiis power ope- 

 rate by the humid or by the dry m ay ? 



The fecrets of nature are concealed behind a thick veil, which is feldom to be penetrated. 

 Too often it happens, that when we think ourfelves in pofTelTion of the obje£\ of our enquiry,. 

 wc find ourfelves deceived by the varying powers around us, which exliibit new forms. Ihe 

 prefumptuous fplrit of m.ni becomes impatient ; cool experimental invcftigation is laid 

 afulc; the powers of im.igination are recurred to, and a region of chimerical images prefents. 

 itfelf. Vanity and indolence both cont'pire to render the philofopher a creator of hypo- 

 thetical worlds. Under thcfe clrcumftances it is not furprifing that a variety of difcordant 

 theories have been invented concerning the production of rock cryflal ; that imaginary 

 rcafoning has been, offered and received, and that no chcniill has yet fucceeded in the ar- 

 tificial produftion of this fubflance. 



The extent of our deductions by analogy is, that filcx, before its crydallization, muft 

 have been diflblved in fomc liquid ; but the queftion is to determine which ? In fire this is 

 not credible, for filex is apyrous. In acids ? — Except the acid of fluor there is no other 

 which acts on this earth, and this acid is a folvent which would not have again been fe« 

 parated. 



Bergman has indeed allured us, th.U he found hard cryftals having the form of rock cry* 

 ftal, in the fluate of filex ; but as he did not carefully examine them, we may ftill q^uellioa 

 •whether they were true rock cryllal. 



Achard likev.ife attempted to imitate nature, and- endeavoured, as is well known, to com-. 

 pofe even the precious (lones, by means of carbonic acid; but it is alfo known that his no- 

 tions were not confirmed, and that this celebrated man either deceived himfelf, or was de- 

 ceived by others ; for his excellent charafter abfolutely forbids the fufpicion of voluntary 

 deception. 



It is known that the alkalis are capable of dilTolving filex; it is alfo known that the acids 

 only are capable of deftroying this combination. The filex in that cafe, when the folutioa 

 is weak, falls down. The precipitate is very fine and tranfparent. When the folution is 

 more faturated, it a/Tumes the form o£ a jelly, or appears like gelatinous condenfed flakes, 

 but never in cryftals. 



Profeflbr Siegling the elder, my intimate friend, had prepared the liquor of flints after 

 the ordinary proccfs, which he fet adde in a glafs veflel covered vrith paper. This fluid 

 remained undifturbed for eight years, when by accident his attention was direfltd to it, 

 and he remarked a beautiful cryllallization. On this occafion he had the goodnefs to fend 

 me the veflel. 



It was a jar of greenifli glafs, capable of holding twelve ounces. The bottom was covered 

 with a number of fmall cryllals, over which repofcd about two ounces of a very tranfparent 

 fluid. This liquid was covered with a cryftalline cruft, fo (Irong that the vefliel could be- 

 inverted without any lofs of the fluid. 



The jar was then broken, and the contents more particularly examined. 



The cryftals at the bottom were compofcd of fulphate of pot-a(h, and cauflic pct-a(h, ia 



a cryftaliized (late. The fluid exhibited the appearance of a caullic lixivium; but which 



had attiactcd a fmall quantity of carbonic acid, and dill contained a little filex. Hence 



7 it 



