BY COMPPvESSION. 3()7 



whiclij in this sluggish state, wouhl be little disposed to move, 

 being confiaed in its original situation by contiguous beds of 

 more refractory matter, would crystallize, without undergoing 

 any change of place, and constitute one of those beds of whin- 

 stone which frequently occur interstratified with sandstone and 

 limestone. 



In other -cases where the heat was more intense, the beds of 

 sand, approaching more nearly to a state of fusion, would ac- 

 quire such tenacity and toughness, as to allow themselves to be 

 bent and contorted, without laceration or fracture, by the in- 

 fluence of local motions, and might assume the shape and cha- 

 racter of primary schistus : the limestone would be highly 

 crystallized, and would become marble, or, entering into thin 

 fusion, would penetrate the minutest rents in the form of cal- 

 careous spar. Lastly, when the heat was higher still, the sand 

 itself would be entirely melted, aiid might be converted, by the 

 subsequent effects of slow . cooling, into granite, sienite, &c. ; 

 in some cases, retaining traces of its original stratification, and 

 constituting gneiss and stratified granite ; in others, flowing 

 into the crevices, and forming veins of perfect granite. 



In consequence of the action of heat, upon so great a quan- The manner hi 

 tity of matter, thus brought into a fluid or semifluid state, and Ja^^e^e mos?*" 

 in which, notwithstanding the great pressure, some substances probably heav- 

 would be volatilized, a powerful heaving of the superincumbent *^ ^ ^^'^^ ^^' 

 mass must have taken place ; which, by repeated efforts, suc- 

 ceeding each other from below, would at last elevate the strata 

 into their present situation. 



The Huttonian Theory embraces so wide a field, and com- 

 prehends the laws of so many powerful agents, exerting their 



h well known. I have seen ti set of large and broad crystals of ice, 

 like the blade of a knife, formed in a mass of clay, of such stiffness, 

 that it had been just used to makes cups for chemical purposes. In 

 many of my former experiments, I found that a fragment of glass 

 made from whinstone or lava, when placed in a muffle heated to the 

 melting point of silver, assumed a crystalline arrangement, and un- 

 derwent a complete change of character. During this change, it 

 became soft, so as to yield to the touch of an iron rod ; yet retained 

 such stiffness, that, lying untouched in the muffle, it preserved its 

 shape entirely ; the sharp angles of its fracture not being in the 

 least blunted. 



R r 2 influ- 



