In two directions I should like to have improved the book; first, it has occasionally happened that a reference could not be verified, owing to the distance at which I live from the great libraries: second, it will be felt at many points, that the book ought to have been illustrated; the expense has deterred me from an adornment of the pages which I recognise to be almost necessary. For the first time in my life I have made an index to my book, for which, rough as it is, my readers will be grateful.
{{comment.content}}