Washmgton, April 19, 1856, - Much activity exists in the agricultural branch of the Patent Office, under the direction of Mr. J. D. Brown. A number of gentlemen, in various parts of the country, are engaged in making experiments in agricultural chemistry, and several interesting reports have just been received.

One, from Dr. Charles T. Jackson, of Boston, who has analyzed the corn cob, acquaints the Bureau that it contains four and a half parts of nutritive matter, consisting of gum, starch, and dextrine.

Another, from the same gentleman, who has made geological excursions through the States of North Carolina, South Carolina, and Georgia, furnishes the result of chemical researches on the seed of the cotton plant. He says that cotton seed may be profitably employed in the production of a rich, fat oil, and that the woolly fibre adhering to the hulls may be economised in the manufacture of paper, while the substance of the seeds, or their "meats," after having the oil extracted, may be employed for feeding animals, and also as an excellent fertilizer.

The following is the analysis of the oil cake, made from the cotton seed: Carbon, 37,740; oxygen, 39,663; nitrogen, 7,753; hydrogen, 6,869; salts (inorganic), 8,960; total, 99,985.

On separating the various salts, and reducing them to their ratios for one hundred grains of the oil cake, the following results were ascertained: Alkaline salts, soluble in water, 0.1.3; phosphate of lime, 3.04; potash, 0.46; soda, 0.53; phosphoric acid, with traces of sulphuric acid and chlorine, 0.80; Bilica and oxides of iron and manganese, 0.18; loss, 0.35. Total, 5.50.

The analysis of cotton seed justifies and explains the use made of them by the Southern planters in preparing the soil with the rotted seeds, as a special manure for Indian corn, which draws so largely on the oil for phosphates.

The Bureau has been sending out small tubers of the Chinese yam, which was recently introduced into France from the North of China, and bids fair to serve as a substitute for the potato.

Arispe, Bureau Co., III., March 9,1856. Dear Sir: Our winter has been the most severe that has been known lately. Peach-trees are all dead, old and young; cherries also, all the Heart and Bigarreau varieties. Pears, also, are nearly all dead; few varieties, probably, will leaf out; but whether they will live through the summer, time will only tell. Plums are also badly used. Roses are killed to the ground - all the ever-blooming sorts that I have examined. Apples, I think, are not injured. I have two Napoleon Bigarreau trees, six years old, budded upon the Morello stock, four feet up from the ground; they are unharmed. Also, one other variety, name not known, budded up nearly as high, unharmed. My loss in trees, etc, winter killed, about 2$00 dollars; rather hard luck for a new beginner, but I am not the only one; it is universal all through this section of country.