The issue of protection to slavery in the Territories, and a Congressional slave code, which is so warmly agitated by the Southern portion of the Administration Democracy, really seems to us destitute of any prominent practical bearing; while the opinions of Mr. DOUGLAS, which are deemed absolutely heretical, and at war with the dearest interests of the South, are justly viewed by many as innocent abstractions. Let us glance for a moment at this subject by the light of reason and experience, and see what can be made of it.

We are told, for instance, that the protection of Congress is indispensable in order that slavery may be planted in various portions of the territory of the United States. Against this view it is alleged that slavery is essentially dependent upon soil and climate; that it may be transplanted, but cannot be made to thrive where its labor will be less profitable than that of the white man. Hence, human effort, while it may force slavery into northern latitudes, cannot possibly keep it there. Certainly these opinions appear to be sustained as well by observation as by argument. It is now pretty generally admitted that Kansas, if left to herself, would never have been a slaveholding State. Those whose ardent desire is to extend the institutions of the South would doubtless have endeavored to graft slavery upon Kansas, but it would have languished and finally disappeared, just as in the neighboring State of Missouri the institution is now languishing, and is doomed unquestionably to eventual extinction.

But suppose slavery were free to go wherever it pleased; suppose Congressional protection were extended to it throughout the Territories of the United States, would the spread of the institution be greatly promoted? We doubt it. The existing Territories are Nebraska, New Mexico, and that vast expanse extending between Kansas and Utah. With the exception of New Mexico, much the larger portion of this region is north of the old Missouri Compromise line. The climate is for the most part exceedingly cold and ungenial, and the soil rugged and imperfectly adapted to cultivation. Slave labor could not be rendered remunerative in those latitudes, and though it might be carried thither it would prove but a sickly exotic. The home of the black race is within or near the Tropics. There he luxuriates in life and vigor, and there he may be usefully employed in a species of toil which to him is natural and healthy, though it would be insupportable and even deadly to the white man. We have cited Missouri as an illustration of the impossibility of maintaining slavery in a land unsuited to it. In that commonwealth a formidable emancipation party now exists, and its efforts cooperating with individual interests, will ere long drain Missouri of her servile population. In Maryland a similar disposition begins to prevail, and nothing save the insane violence and folly of the Abolitionists has retarded the growth and influence of this feeling in Virginia and Kentucky. Men, under the stimulus of excitement, will for a while persist in acting in opposition to their obvious interests; but this cannot last long. We even now perceive that while the frontier slave States are professedly denouncing Northern sectionalism with the utmost fury, they are sedulously engaged in ridding themselves of their slaves as rapidly as possible, by transferring them to an extreme Southern market.

This reflection conducts us to another branch of the topic. Granting that Congress acceded to the prayer of the Southern Democracy; admitting that a slave code and protection to slavery in the Territories flourished in full and undisputed vigor, we should like the philosophers and political economists to inform us where the slaves are to come from, that the various Territories may be peopled by them. How stands the case at present? Every negro that is taken from Virginia or Kentucky to the cotton and sugar States of the South commands a price far exceeding his value at home, because his labor is more essential and more profitable in Louisiana, Texas, and Mississippi than it can possibly be in the Northern slave States. So true is this that there is a constant exodus of slaves from the latter. The demand for slave labor throughout the cotton belt is enormous and constantly increasing. As the culture of that great staple yearly extends, so is the necessity of field hands more strongly experienced. Hence the regular and rapid enhancement in their value. Cotton, too, continues to command handsome remunerative prices, because, immense as is the crop, it does not exceed the demand. The four and a half millions of bales which this year will be brought to market will not do more than supply the wants of Europe and America, and if, as is not unlikely, the production next year should reach five millions, the only effect will be to stimulate manufactures without lowering the price of the article. Meanwhile, negroes will be in constant demand. Every new plantation opened; every acre of virgin soil planted with cotton increases the necessity for slave labor, and augments its value. Is it not readily seen that this condition of affairs must ultimately tend to empty the Northern slave States, and to concentrate the servile population in the cotton growing region? Do not the exorbitant prices now paid for negroes show that, vast as is the supply, it is hardly equal to the perpetually increasing want? And if such be the case—if there are scarcely negroes enough to perform the work required of them in the existing slave States, where is the new supply to come from which would go to people the Territories, in the event that they were thrown open to slavery? Is it not clear that we have not more slaves than are needed for Southern plantations; and that if we undertake to discover new fields for their labor, we should, as an essential prerequisite, provide the means for a fresh supply? Is there anybody so verdant as to imagine that while this Union lasts, Congress will ever consent to reopen the slave trade? Of what possible use then is it to discuss questions as practically unavailable, as some of the theological problems on which the early Christian fathers were wont to indite elaborate folios of learned speculation?