_ The writer has availed himself of the opportunity of a new edition to add three or four additional illustrations in the footnotes. The criticisms on the first edition call for no remark, excepting this, perhaps, that the present little volume has no pretensions to be anything more than an Essay. To judge such it performance as if it professed to be an exhaustive Treatise in casuistry, is to subject it to tests which it was never designed to bear. Merely to open questions, to indicate points, to suggest cases, to sketch outlines,--as an Essay does all these things,--may often be a process not without its own modest usefulness and interest.
May 4, 1877. _