81 



CHAP. XXIV. 



Granite. 



IF the remarks on the unstratified rocks have antici- 



A 



pated much of the history of Granite, their effect has 

 also heen to produce repetitions, not limited to this 

 rock alone, yet inseparable from the plan of this work, 

 without a sacrifice of utility to literary neatness. The 

 term Granite is so current, and the substance so fami- 

 liar, that it seems superfluous to define it. Yet there 

 is no rock respecting which geologists have more mis- 

 understood each other. Nature has thrown consider- 

 able obscurity into the subject, and they have, too often, 

 so managed as to increase it. This confusion has 

 arisen chiefly from viewing it as defined and distin- 

 guished by nature ; whereas, if considered as a genus 

 or family, it must be on artificial or conventional 

 grounds, unless we are to go on in darkness and dis- 

 putation for ever. 



The term Granite has, by some, been limited to a 

 compound of quartz, felspar, and mica, and the word . 

 Syenite adopted for those containing hornblende; 

 laying the foundation of a large progeny of errors. 

 The distinction is as unfounded as it is pernicious. To 

 the first compound there is sometimes superadded 

 hornblende, or else it becomes a substitute for the 

 mica, producing a granite even more abundant than 

 the first ; while the ternary compounds also lose one 

 or other of their ingredients, and become binary ; all 

 these varieties further occurring in the same mass, 

 and often within a very small space. In Nature, 

 therefore, Granite ranges within four essential mi- 

 nerals, quartz, felspar, mica, and hornblende, in dif- 



VOL. II. G 



