It was with considerable reluctance that I felt myself compelled to discard the system of coloration adopted in the Geological Survey Maps; and rids I did only after the strongly expressed opinion of several geologists.

It was not that I have any very intense desire to colour rocks after their natural tints, but I have an aversion to adopting a colour suite which departs markedly therefrom; or one which is in discordance instead of harmony therewith. One friend, a man of great scientific discretion, and himself an artist, writes me that when he looks at a recently published geological Map of Scotland, with its grey Torridon and its red Laurentian, he does not know whether he is standing on his head or his heels.