Dr. Mac Culloch 07i Qjiartz Rock. 457 



obvious that there is no provision made for this rock in Werner's 

 classification, if I have succeeded in proving that it is as little entitled 

 to the name of quartz, as to that of granite, and that it is not a 

 purely primitive and chemical deposit. Its mechanical structure 

 deprives it of a right to the latter title, and its connexions and dis- 

 position prevent us equally from arranging it w^ith the latest stratified 

 or *'floetz" rocks. If it is a necessary condition of the "transition'* 

 rocks to contain organic remains, then this rock is also excluded 

 from the intermediate or transition class, as much by this as by its 

 position in respect of the mica slate, universally esteemed among the 

 primitive, or to speak more properly among the most ancient rocks. 

 Such are the inconveniences of artificial arrangements, whether 

 they are groundless, or founded on partial views of natural pro- 

 ductions. It has been proposed indeed to call this rock graywacke, 

 a quartzose graywacke. But this is in fact to confound all dis- 

 tinctions for the sake of an adherence to a system, which may 

 without disgrace admit a new member into any of its series, should 

 it appear that a member hitherto unobserved does actually exist. 

 The name graywacke has been already too much abused, and is 

 become a fruitful source of confusion and error. It is incumbent on 

 us to diminish instead of increasing this evil, by a more careful 

 application of that, as well as of other geological terms, and by 

 limiting its use within the rigid compass of definition. On that 

 definition I need not now insist ; nor will I attempt at present to 

 assign the true place of the quartz rock in the general arrangement. 

 It will be done with greater facility when I have described its 

 connexions in the other places where I have observed it. 



Vol. II. 3 m 



