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