Mineralogy of Sky. 161 



there will be found a transition, unexpected and improbable as it 

 may at first seem, between the two series, that of the gneiss, and 

 that of the graywacke and sandstone which follows it ; but at what 

 point between the two extremities of the gneiss boundary a decided 

 change takes the place of a gradual transition it will be for ever 

 impossible satisfactorily to determine. I must add that the limit of 

 the gneiss series on the eastern side of Sleat is the sea shore itself. 



I must now proceed, before entering further on the transition of 

 the gneiss series, to describe that which in the original paper I 

 called the series of blue quartz rock and schist, in which there is 

 somewhat to amend and somewhat to supply. With this I must 

 here include the red sandstone, formerly separated from the other 

 two rocks on the same systematical views which led into the other 

 errors already mentioned. The conclusions then drawn were suf- 

 ficiently justified by the partial view of the country which I had at 

 that time obtained, but they were founded on observations too 

 limited. A more complete investigation, with a greater disregard 

 of theoretic views, would not only have led to sounder conclusions, 

 but have removed many difficulties which I encountered both in 

 the examination and in the attempt to reconcile discordant phe- 

 nomena. 



Although on reviewing the places I examined before, I find the 

 description formerly given of these substances locally correct, and 

 the conjecture I had formed of the nature of the rocks toward the 

 Kyle ri'ch equally so, yet an examination of additional parts of this 

 series renders it necessary to remodel the whole description, as it 

 possesses a degree of intricacy which it was impossible to suspect, 

 and which nothing but a very accurate examination could ever 

 have induced me to credit, since it is at variance with the usual 

 phenomena that attend these rocks. 



