A. P., (Northampton, Mass.) The difference between the Virginia Creeper, (or Ampilopsis.) a harmless plant, and the poi son sumac, or Mercury vine, (Rhus toxicodendron,) which somewhat resemble each other, as you, say, is, that the former has five leaflets in a cluster, and the latter only three. They both cling to stone-walls by the little rootlets sent out from the stem.

The National Ignorance of the Agricultural Interest.

TO general observers, the prosperity of tie United States in the great interests of trade, commerce, manufactures, and agriculture, is a matter of every-day remark, and general assent. The country extends itself from one zone to another, and from one ocean to another. New states are settled, our own population increases, emigration pours its vast tide upon our shores, new soils give abundant harvests, new settlements create a demand for the necessaries and luxuries of life provided by the older cities, and the nation exhibits at every census, so unparalleled a growth, and such magnificent resources, that common sense is startled, and only the imagination can keep pace with the probable destines of the one hundred millions of Americans that will speak one language, and, we trust, be governed by one constitution, half a century hence.

As a wise man, who finds his family increasing after the manner of the ancient patriarchs', looks about him somewhat anxiously, to find out if there is likely to be bread enough for their subsistence, so wise statesmen, looking at this extraordinary growth of population, and this prospective wealth of the country, will inquire, narrowly, into its productive powers. He will desire to know whether the national domain is so managed that it will be likely to support the great people that will be ready to lire upon it in the next century. He will seek to look into the present and the future sufficiently to ascertain whether our rapid growth and material abundance, do not arise almost as much from the migratory habits of our people, and the constant taking-up of rich prairies, yielding their virgin harvests of breads tuffs, as from the institutions peculiar to our favored country.

We regret to say, that it does not require much scrutiny on the part of a serious inquirer, to discover that we are in some respects like a large and increasing family, or do care to preserve or maintain it, rather than a wise and prudent one, seeking to maintain that estate m its best and most productive condition.

To be sure, our trade and commerce are pursued with a thrift and sagacity likely to add largely to our substantial wealth, and to develop the collateral resources of the country. But, after all, trade and commerce are not the great interests of the country. That interest is, as every one admits, agriculture. By the latter, the great bulk of the people live, and by it all are fed. It is clear, therefore, if that interest is neglected or misunderstood, the population of the country may steadily increase, but the means of supporting that population, (which can never be largely a manufacturing population,) must necessarily lessen, proportionately, every year.

Now, there are two undeniable facts at present staring us Americans in the face - amid all this prosperity: the first is, that the productive power of nearly all the land in the United States which has been ten years in cultivation, is fearfully lessening every season, from the desolating effects of a ruinous system of husbandry; and the second, is, that in consequence of this, the rural population of the older states is either at a stand still, or it is falling off, or it increases very slowly in proportion to the population of those cities and towns largely engaged in commercial pursuits.

Our census returns show, for instance, that in some of the states, (such as Rhode Island, Connecticut, Delaware and Maryland,) the only increase of population is in the towns - for in the rural population there is no growth at all. In the great agricultural state of New-York, the gain in the fourteen largest towns is sixty-four per cent, while in the rest of the state it is but nineteen per cent. In Pennsylvania, thirty-nine and a quarter per cent in the large towns, and but twenty-one per cent in the rural districts. The politicians in this state, finding themselves losing a representative in the new ratio, while Pennsylvania gains two, have, in alarm, actually deigned to inquire into the growth of the agricultural class, with some little attention. They have not generally arrived at the truth, however, which is, that Pennsylvania is, as a state, much better farmed than New-York, and hence the agricultural population increases much faster.

It is a painful truth, that both the press and the more active minds of the country at large, are strikingly ignorant of the condition of agriculture in all the older states, and one no less painful, that the farmers, who are not ignorant of it, are as a body, not intelligent enough to know how to remedy the evil.

"And what is that evil?" many of our readers will doubtless inquire. We answer, the miserable system of farming steadily pursued by eight-tenths of all the farmers of this country, since its first settlement: a system which proceeds upon the principle of taking as many crops from the land with as little manure as possible - until its productive powers are exhausted, and then------emigrating to some part of the country where they can apply the same practice to a new soil. It requires far less knowledge and capital to wear out one good soil and abandon it for another, than to cultivate a good soil so as to maintain its productive powers from year to year, unimpaired. Accordingly, the emigration is always "to The West" There, is ever the Arcadia of the American farmer; there are the acres which need to yield their thirty or forty bushels of wheat to the acre. Hence, the ever fall tide of farmers or farmers sons, always sets westward, and the lands at home are left in a comparatively exhausted and barren state, and hence, too, the slow progress of farming as an honest art, where every body practices it is like a highway robber.

There are, doubtless, many superficial thinkers, who consider these western soils exhaust less - "prairies where crop after crop can be taken, by generation after generation." There was never a greater fallacy. There are acres and acres of land in the counties bordering the Hudson - such counties as Dutchess and Albany - from which the early settlers reaped their thirty to forty bushels of wheat to the acre, as easily as their great grand-children do now in the most fertile fields of the valley of the the Mississippi. Yet these very acres now yield only twelve or fourteen bushels each, and the average yield of the county of Dutchess - one of the most fertile and best managed on the Hudson, is at the present moment only six bushels of wheat to the acre! One of our cleverest agricultural writers has made the estimate, that of the twelve millions of acres of cultivated land in the state of New-York, eight millions are in the hands of the "skinners," who take away everything from the soil, and put nothing back; three millions in the hands of farmers who manage them so as to make the lands barely hold their own, while only one million of acres are well farmed, so as to maintain a high and productive state of fertility.

And as New York is confessedly one of the most substantial of all the older states, in point of agriculture, this estimate is too flattering to be applied to the older states. Even Ohio - newly settled as she is, begins to fall off per acre, in her annual wheat crop, and before fifty years will, if the present system continues, be considered a worn out soil.

The evil at the bottom of all this false system of husbandry, is no mystery. A rich soil contains only a given quantity of vegetable and mineral food for plants. Every crop grown upon a fertile soil, takes from it a certain amount of these substances, so essential to the growth of another crop. If these crops, like most of our grain crops, are sent away and consumed in other counties, or other parts of the counties - as in the great cities, and none of their essential elements in the way of vegetable matter, lime, potash, etc., restored to the soil, it follows as a matter of course, that eventually the soil must become barren, or miserably unprofitable. And such is, unfortunately, the fact. Instead of maintaining as many animals as possible upon the farm, and carefully restoring to the soil in the shape of animal and mineral manure, all those elements needful to the growth of future vegetables, our farmers Send nearly all their crops for sale in cities - and allow all the valuable animal and mineral products of these crops to go to waste in those cities.

"Oh! but," the farmer upon worn out land will say, "we cannot afford to pay for all the labor necessary for the high farming you advocate." Are you quite sure of that assertion? We suspect if you were to enter carefully into the calculation, as your neighbor, the merchant; enters into the calculation of his profit and loss in his system of trade, you would find that the difference in value between one crop of 12 bushels and

* In Belgium - the most productive country in the world, the urinary excrements of each cow arc sold for $10 a another of 30 bushels of wheat to the acre, would leave a handsome profit to that farmer who would pursue with method and energy, the practice of never taking an atom of food for plants from the soil in the shape of a crop, without, in some natural way, replacing it again. For, it must be rememembered, that needful as the soil is, every plant gathers a large part of its food from the air, and the excrement of animals fed upon crops, will restore to the soil all the needful elements taken from it by those crops.

The principle has been demonstrated over and over again, but the difficulty is to get farmers to believe it. Because they can get crops, such as they are, from a given soil, year after year, without manure, they think it is only necessary for them to plant - Providence will take care of the harvest. But it is in the pursuit of this very system, that vast plains of the old world, once as fertile as Michigan or Ohio, have become desert wastes, and it is perfectly certain, that when we reach the goal of an hundred millions of people, we shall reach a famine soon afterwards, if some new and more enlightened system of agriculture than our national "skinning" system, does not beforehand spring up and extend itself over the country.

And such a system can only be extensively disseminated and pat into practice by raising the intelligence of farmers generally. We have, in common with the Agricultural Journals, again and again pointed out that this is mainly to be hoped for through a practical agricultural education. And yet the legislatures of our great agricultural states vote down, year after year, every bill reported by the friends of agriculture to establish such schools. Not one such school, efficient and useful as it might be, if started with sufficient aid from the state, exists in a nation of more than twenty millions of farmers. "What matters it," say the wise men of our state legislatures, "if the lands of the Atlantic states are worn out by bad farming? Is not the great west the granary of the world?" And so they build canals and railroads, and bring from the west millions of bushels of grain, and send not one fertilizing atom back to restore the lands. And in this way we shall by-and-bye make the fertile prairies as barren as some of the worn out farms of Virginia. And thus "the sins of the fathers are visited upon the children, even to the fourth generation!"