SIR,--I have duly received your favor of March 28th, and with it your treatises on the culture of the sugar cane and cotton plant in France. The introduction of new cultures, and especially of objects of leading importance to our comfort, is certainly worthy the attention of every government, and nothing short of the actual experiment should discourage an essay of which any hope can be entertained. Till that is made, the result is open to conjecture; and I should certainly conjecture that the sugar cane could never become an article of profitable culture in France. We have within the ancient limits of the United States, a great extent of country which brings the orange to advantage, but not a foot in which the sugar cane can be matured. France, within its former limits, has but two small spots, (Olivreles and Hieres) which brings the orange in open air, and _à fortiori_, therefore, none proper for the cane. I should think the sugar-maple more worthy of experiment. There is no part of France of which the climate would not admit this tree. I have never seen a reason why every farmer should not have a sugar orchard, as well as an apple orchard. The supply of sugar for his family would require as little ground, and the process of making it as easy as that of cider. Mr. Micheaux, your botanist here, could send you plants as well as seeds, in any quantity from the United States. I have no doubt the cotton plant will succeed in some of the southern parts of France. Whether its culture will be as advantageous as those they are now engaged in, remains to be tried. We could, in the United States, make as great a variety of wines as are made in Europe, not exactly of the same kinds, but doubtless as good. Yet I have ever observed to my countrymen, who think its introduction important, that a laborer cultivating wheat, rice, tobacco, or cotton here, will be able with the proceeds, to purchase double the quantity of the wine he could make. Possibly the same quantity of land and labor in France employed on the rich produce of your Southern counties, would purchase double the quantity of the cotton they would yield there. This however may prove otherwise on trial, and therefore it is worthy the trial. In general, it is a truth that if every nation will employ itself in what it is fittest to produce, a greater quantity will be raised of the things contributing to human happiness, than if every nation attempts to raise everything it wants within itself. The limits within which the cotton plant is worth cultivating in the United States, are the Rappahanock river to the north, and the first mountains to the west. And even from the Rappahanock to the Roanoke, we only cultivate for family use, as it cannot there be afforded at market in competition with that of the more Southern region. The Mississippi country, also within the same latitudes, admits the culture of cotton.