Ch the Hutionian Theory of the Earth, ' tot 



Laftly, I muft add, that even on the fuppofition that diftinft cryftals of quartz, felfpar, 

 and mica, could be produced by fuCon, they ftill would be far from refembling thofe wc 

 are acquainted with, which eflentially contain feme particles of water, as I have elfewhere 

 (hewn. 



Perhaps fome may fay, that the fame difficulties occur in accounting for the cryftaliza- 

 tion of granite in the moid way ; on mature confideration, however, it will readily be feen, 

 that the caufes of coadinution in the dry and moid way are very different, and that their 

 cfFedls fhould alfo be different ; for fuppofing the earths that enter into the compofition of 

 granites difTolved in the moift way, their precipitation arid imperfe£t cryftalization may be 

 afcribed to the union they contrail with each other, forming mafTes of each of the conlli- 

 tuent ingredients of granite, which water can no longer hold fufpended ; hence the preci- 

 pitation of each of the three fpecies of ftone is nearly contemporaneous, whereas if the 

 formation of thefe ingredients fliould take place in the dry way, it would necefTarily be 

 fuccefhve keeping place with the fuccefhve diminutions of heat, and then the above-men- 

 .tioned confequences would naturally enfue. 



The ftate of the granatic ingredients in' fufion, which I have above given, agrees pretty 

 nearly with that prefented by Sir James himfelf ; he fuppofes the quartz felfpar, fhorl, 

 mica, and garnet, &c. melted together, and the moft fufible of them to be the menftruum 

 in which the reft are difTolved, and that they differ from each other in their properties of 

 folution, as falts differ from each other. Some of them being more foluble in the men- 

 ftruum when very much heated, than when ic is comparatively cold, and others may be 

 foluble in it when little warmer than its point of congelation. " If then we fay, for in- 

 " ftance, that the congealing point of the folvent is 1000° of Fahrenheit, and if the folu- 

 *' tlon is at the temperature of 2000°, we may conceive one portion of the matters dif- 

 '• folved, as held by tlie fimple difTolving power of the menftruum, and another as held by 

 " means of its elevated temperature ; when therefore a mafs of this kind is allowed to cool 

 •' very flowly, thofe fubftances held in folution by the heat of the folvent, will firft feparate, , 

 *' and being forme.* in a liquid, will affume their cryftaline form with regularity." This 

 confequence is truly deduced from the Baronet's hypothefis, but being contrary to faft, . 

 difcovers the falfhood of that hypothefis ; for if any of the fore-mentioned component parts 

 of granite can be faid to be held in folution by the high heat of the folvent, it is furely the 

 quartz ; now the quartz is fcarce ever found regularly cryftalized when forming a compo- 

 nent part of granite, as all mineralogifts atteft, and is a matter of univerfal obfervation. 



" But the Baronet continues — " whereas thofe fubftances which were held by the men- 

 " ftruum fimply as a fluid, will not feparate until the congelation of the folvent itfelf takes 

 •' place, when the cryftals of the various fubftances will intermix and confound the regu- 

 " larity of form which each would have affumed if left to itfelf. In this manner one of the 

 "common kinds of granite will be produced, confifting of perfe£l cryftals of fliorl, mica," 

 "or garnet, inclofed in a confufed mafs of felfpar, quartz, and fhorl."— This conclufion 



is 



