MY dear sir J ohn, — The age of formal dedications and stilted prefaces has long passed away, and it may safely be assumed that they ceased to be written, because the public ceased to read them. As often happens in like cases, all parties gained by the arrangement; and I have no intention whatever of reviving an obsolete custom. Yet something in the nature of an introduction is often a great advantage both to the writer and the reader; and I think in the pres ent instance the latter will turn the pages over with more satisfaction, if the circumstances under which the book has been written and the principal objects kept in view by the writer are first understood.