226 GRANITE* 



mineral composition, cannot be traced in the 

 same manner to a leading mass. 



Granite masses are sometimes continuous for 

 a great space ; so that they possess no definite 

 form ; or, if any such form be present, it cannot 

 be discovered. At other times, they are dis- 

 posed in large definite bodies, not unaptly com- 

 pared to feather beds,' separated by fissures or 

 joints. When these masses possess a large di- 

 .mension in two directions only, they often re- 

 semble the beds of stratified rocks, and have 

 sometimes been mistaken for true strata. Occa- 

 sionally, these dimensions are so proportioned, 

 that they resemble irregular spheroids : but these 

 forms appear to have resulted from the wearing 

 of the angles of masses originally prismatic. 



The extended beds above mentioned, are fre- 

 quently subdivided by fissures into smaller pris- 

 matic and cuboidal masses; and as this subdi- 

 vision generally takes place in two opposite 

 directions, or are vertical and parallel to the 

 great mass or bed, these prisms are found piled 

 on each other in a manner resembling huge 



