Among most of the geologists who had of late years been engaged in investigating the structure of the North-West Highlands, and especially among those who did not concur in Murchison's explanation of the phenomena exhibited there, it was a growing belief that great overthrusts had been largely instrumental in producing the remarkable stratigraphical relations of the rock masses of that region. After a most careful detailed examination of the ground by the Geological Survey, the existence and importance of such thrusts was not only placed beyond a doubt, but a variety of additional remarkable structures were discovered, which open up new fields of investigation to the physical geologist.