A DIFFICULT AND DELICATE SUBJECT PROPOSED.--AGITATION OF IT UNAVOIDABLE.--CHRISTIANS NORTH AND SOUTH SHOULD GIVE THE DISCUSSION OF IT A RIGHT DIRECTION.--WE ARE ALL INTERESTED IN THE ISSUE.--NORTHERN DISCLAIMERS. MY DEAR CHRISTIAN BROTHER,--In my last I intimated that I hoped you and I, by our correspondence, would be able to furnish the world a practical illustration of good-nature and kind feeling in the discussion of a subject that has been a fruitful source of trouble and unchristian invective. You have already anticipated my theme--it is DOMESTIC SLAVERY. It must be confessed that this is the most difficult and delicate of all topics to be agitated by a Northerner and a Southerner, and yet I have the fullest confidence that neither of us will give or take offence. I need offer you no apology for calling your attention to this subject at the present time. Not only is it a theme of vast importance in itself, involving, either directly or indirectly, interests most dear to you and to me, and to every one who has at heart the welfare of his country and his race, but it is a subject that must be discussed,--there is no avoiding it, however much you or I or other individuals may desire it. It has come before the public mind in such a manner as peremptorily to demand the attention of every Christian and every patriot. Whether we approve or deprecate the peculiar causes that have made this topic so prominent in our country, both North and South, we have to take things as they are, and turn them to the best possible account. Politicians and demagogues are all discussing American slavery, and will continue to do so for the purpose of forwarding their own favorite schemes; and any attempt to silence them would be as futile as an effort to arrest the gulf-stream in its course. It remains only for brethren, both at the South and North, to take up the subject as we find it brought to our hands in the inscrutable providence of God, and, under the guidance of his Spirit, given in answer to our prayers, take a truly Christian view of some of its leading features, and then inquire, What is duty? I think you will not claim, with some of your southern friends, that slavery is a subject with which we at the North "have nothing to do." As patriots, we have something to do with every thing that affects the interests of our common country; and as Christians, we sustain responsibilities which we cannot shake off toward all our brethren of the human family, whether it be at the North or South--whether they be bound or free. "Have we not all one Father? Hath not one God created us?" "We are many members, but one body, and whether one member suffer all the members suffer with it; or one member be honored, all the members rejoice with it."