In placing his volume before the tribunal of the public, the author would confess that he is perfectly conscious of its containing some defective points in argument, some reasoning which might be better illustrated, some subjects which as yet cannot be developed beyond a certain extent, or which require a larger experience, and some instances of repetition which might have been avoided. But he is fain to crave a degree of indulgence on the ground of the nature of his subject, of its being greatly an unexplored tract, and containing much of the "terra incognita ;"and of his own active professional duties, which have crowded his literary labours into a very late hour of the night, and which have occasioned frequent interruptions of a most harassing character. Yet he would hope that notwithstanding these difficulties and imperfections, some steps in advance have been taken towards exploring that most important subject, THE RECIPROCAL INFLUENCE OF