Vii. i \cboftbe Mineralogy of Sky, 



published in tl. umt of tht Trwisjttions of the 



( i xety, 



p )N ,1 MacCdlloch, M.D F.L.S President of the Geological Society, 

 Chemist t<> il"- Ordnance, Lecturer on Chemistrj at the Royal 

 Military Academ] . and Geologist t<> the Trigonometrical Shims 



7th, 1817.] 



>\ I UN the Sketch of the Mineralogy of Sky was drawn up for 

 the Society's volume in 181:3,' I had n0 prospect of again visiting 

 that remote country. Circumstances having led me to traverse the 



• riu difference! between th<- map of Sky m bich accompanies this supplementarj paper, 

 and that former!] giren, require tome explanation, thai thi reader* of the (.. 

 Transactions maj be able to appreciate the reaaoni irhich bate led to the alterations, and 

 account for those which, in a geological point of riei . «ill be show n t<> be more 

 than real, and i<> we what degree of confidence thej maj repose in the present one. 



In laying down the places of the different rocks, I former!) made u><- of the documents 

 from which .Mr. Faden'i trareliing m.i|> was constructed, and I was guided in the i ami- 

 nation bj Mackenrie's chart. The incorre c tne ss of these has been the leading 

 the apparent differences in the relatire extent nf the rocks as the] hare been delineated, 

 while th'-ir Insuffidencj for the purposes of s r eticu l um , arising from the great distortions 

 of the- outline of the country and their deficiencies in it-* internal features, pn \< ated ma 

 fiom laying down man] of the places where thi existence oi boundaries of particnli 

 had been accurately ascertained. Hence the geological delineation bore do proportion to 

 tin acenrac] of the observations. To then defecti if there be added the blanks which 

 I nature of the formei survej necessaril] left, the discrepancies of the two «ill 

 not appeal so considerable as the] seem if first -i^in. | ma] also add, that it has been 

 found expedient to change the colours l>) which the different rocks are denoted ', another 



present observationi I hare made use of Mr. anowsxalth's map, with 

 rariationi which I think it at iplain, that the degree of confidenee 



i hi tin r in ih. original w in the alterations, ma) be and rstood. 



