XIX. Remarks on several Parts of Scotland which exhibit ^artz 

 Rocky and on the Nature and Connexions of this Rock in general. 



By J. Mac CuLLOcH, M.D. Chemist to the Ordnance, and Lecturer on 



Chemistry at the Royal Military Academy at Woolwich. 



v. Pr. Geo. Soc. 



Jura. 



.S I considered that the mineraloglcal history of Jura had al- 

 ready been amply detailed, I ascended its well-known mountains 

 rather to gratify my love of the picturesque, than with the hope of 

 acquiring any new ideas on the subject of its structure. 



Yet as the predominant opinions seemed to have determined that 

 the tract in question was composed of a granular quartz, and as it 

 had been compared with the northern part of Scotland asserted to 

 consist of the same rock, with the ridge of Schihaliien, amply 

 described as such by Professor Play fair, and with numerous other 

 foreign rocks described by various authors under this designation, 

 I had with others admitted the term, and the sera of formation which 

 this term implied. My own researches having given me reason to 

 differ in opinion from these authorities, I have thought it necessary 

 to describe the appearances which I saw ; the question of its rank 

 in the great society of rocks can only be determined after all its cir- 

 cumstances have been fully investigated. 



The whole island extending to a length of 30 miles, and varying 



