166 PKOF. T. G. BONNET ON THE LITHOLOGTCAL 



inorphism and may possibly suffice to enable us to group it with I. 

 Its materials, however, are undoubtedly derived from the same source 

 as those which have already beeu described in this group. 



29 (near Duncraig). A darker and less flaggy rock, also appearing 

 but little altered. Microscopically seems to be composed of the same 

 materials, but with less sericite. The smaller quartz-granules are 

 agglutinated ; and the rock may with less hesitation than in the last 

 case be called metamorphic and grouped with series I. 



30 (near Balmacarra Hotel). A dull red mudstone, seemingly 

 little altered. With the microscope a certain amount of meta- 

 morphism is perceived, as in the last case ; so that it, too, may be 

 grouped with series I. There is rather more " sericite " and ferrite. 



31 (Glen Logan). A black compact limestone. This, under the 

 microscope, is more completely crystalline than I should have ex- 

 pected. It is somewhat dolomitic, exhibits no trace of organisms, 

 and contaius a fair amount of opacite (graphite?) in scattered 

 granules and streaky clots. I should expect to find it associated 

 with rocks of the series I. type. 



32 (Loch Kishorn). A dull- coloured compact limestone, traversed 

 by numerous, irregular, thin, cherty veins. Under the microscope 

 it appears to be an intimate mixture of calcite or dolomite with a 

 microlithic mineral, probably quartz. The cherty veins are chalce- 

 donic quartz. I should suggest that this also belongs to series I. 

 group. 



In conclusion I may perhaps be allowed to state that I wrote 

 the rough draft of these notes in ignorance of the bearing of 

 the specimens upon any theoretic views entertained by Dr. Hicks ; 

 that, upon sending it to him, my remarks upon the amount of meta- 

 morphism accorded, in the great majority of cases, with what his 

 stratigraphical arrangement demanded, and differed only in a few 

 instances Avhere I myself was very doubtful, and had left an opening 

 for further consideration. I know very little of the district ; so that 

 these notes are strictly lithological, and -I have thus offered no 

 opiuion as to the geological age of the different series. As to the 

 vexed question of the correlation of the metamorphic rocks of Scot- 

 land, J would, at present, rather say no more than this — that having 

 regard to the teaching of "Wales, Cornwall, and the Alps, very clear 

 evidence will be needed before we can accept the dominant rocks of 

 the Central Highlands as of Lower Silurian age. 



EXPLANATION OF PLATE VI. 



Map showing the Archaean and overlying rocks of parts of Ross- and 

 Inverness- shires. — Scale 4 miles to 1 inch. 



