[ ^3 ] 



*' confound die regiilarity of form which each would have af- 

 '• fumed if left to itfelf. In this manner one of the common 

 " kinds of granite will be produced confifling of perfeft cryflals 

 " of fhorl, mica or garnet inclofed in a confufed mafs of felfpar, 

 " quartz and fliorl." — This conclufion is as objeclionabie as the 

 foregoing ; for not to mention that granites, in which fliorl and 

 efpecially garnets are found, are far from being common, af- 

 furedly fiiorl and garnet approach more to the fufibility of felfpar 

 (the fuppofed menftruum) then either quartz or mica. Thefe 

 therefore are thofe which fhould cryftaliize without any regular 

 form in the Baronet's hypothefis, and not the quartz and mica ; 

 which is juft the contrary of wh^t he himfelf has obferved, for 

 he tells us, p. 9, " he found the cryflals of felfpar regularly 

 " defined." 



Sir James has fince very wifely declined juftifying his theory 



f the formation of granite by fufion, and by the advice of 



lodlor Hope very properly applied himfelf to experiments on 



■Vrious fpecies of wbin, a denomination which in Scotland com- 



pshends grunflein, bafalt, trap, wacken and porphyry, ftones 



inwhich, except the laft, none of the component ingredients 



arfound regularly cryftallized, and on the laft he has made no 



exp-iment. — The former he tells us were foftened or fufed in a 



hea»)f from 38" to 55^ of Wedgwood, the glafles to which they 



wert-educed were foftened on a range of from 15" to 24, and 



the 



