Manures.—The object of cotton-culture is to develop tho quantity and quality of the down which envelops the seeds of tho plants, hence manuring must be conducted with the aim primarily of supplying such constituents as are extracted from the soil by the fructificatory parts of the plant. An analysis of the ash obtained from the incineration of cotton fibre shows that the principal mineral ingredients are potash per cent.), lime (17.09), and phosphoric acid in other words, 10,000 lb. of ootton fibre abstract from the soil, 31 lb. of potash, 17 lb. of lime, and 12 lb. of phosphoric acid. Examinations of different samples of cotton fibre have shown that while New Orleans cotton contains per cent, of phosphoric acid, Surat contains only 0.027 per cent.; this fact has suggested the important question, whether the inferiority of Indian cotton is not due to deficiency of phosphoric acid in the soil.
Analysis of the ash of ootton-seed reveals the presence of per cent. of phosphoric acid, 29.79 per cent, of lime, and 19'40 per cent. of potash. The seed is thus much more exhaustive than the fibre, and when its much greater proportion is taken into account, it is probably not an exaggeration to eay that while the cotton fibre (or " lint," as it ie Galled) alone takes no more than 4 lb. of soil ingredients for every bale of cotton, the seed accompanying it takes about 38 lb. If the seed, therefore, after expression of the oil (see Oile), be made into cattle-food, and be returned in the form of cattle-dung to the ground, the crop will be one of the least exhaustive known ; but if the seed be permanently removed from the land, heavy manuring will be necessary to maintain fertility.
The analyses indicate that the manures best adapted to the end in view are superphosphate of lime (supplying both phosphoric acid and lime), and potash (either wood-ashes, or natural potash salts); and that nitrogenous manures—guano, nitrate of soda, sewage, &o.—should be avoided, as forcing the plant to produce wood and leaf, rather than flower and fruit. Salt appears to be peon liarly beneficial.
All refuse from the plant ehonld be returned to the soil, either by being burnt, and the ashes ploughed in, or by allowing cattle to feed upon it on the ground. The stems contain a fibre, about which extravagant ideas have been current. It is probable that any attempt to improve this fibre would be at the expense of the seed-down, or it would entail so much extra manuring that the end would not warrant the means.
Diseases and Enemies.— The cotton plantations of America have long been infested by two most destructive insects—the cotton-worm (Aletia argillacea) and the boll-worm (Heliothis armigera). The former has been credited with the ruin of 38-98 per cent. of the whole crop on some estates.
The highest average of loss is in the southern portion of the cotton-belt, as in Florida and S. Texas ; it increases also in a westerly direction, commencing with Georgia at 16 per cent., and ending with Texas at 28 per cent. ; in the northern portion of the belt, the averages are low, ranging from 5 to 8 per cent., while in many parts, notably N. Carolina, the caterpillar appears so late as to generally do more good than harm, by destroying the top foliage, and admitting the sun.
The moth from which this caterpillar originates appears either to hibernate in the cotton districts in the moth state, or to emigrate annually from warmer regions, as the Bahamas. Its predilection for sweets affords the most likely means of arresting its ravages. Arseniate of copper, mixed with honey, and applied to tree-stems, &o., abont the estate, may kill the first moths, and check the pest at once. When the worms are hatched, they feed on the under side of the leaves, and can then only be reached by an upward sprinkling of a poisonous solution, generally arsenical.
Separation of the Fibre.—Cotton-ginuing, or the separation of the fibre from the seed, is always performed in the vicinity of its growth. Seed cotton only yields 15-30 per cent, of fibre, but the separated esed possesses valuable qualities, and is carefully preserved.
Ginning is the first process to which the fibre is subjected ; without the gin, or its equivalent, the cultivation and manufacture of cotton on its present extended scale would have been en impossibility. The important inventions that took place in Lancashire during the 18th century led to the introduction and extended cultivation of cotton in the S. States of America, and, towards the close of the century, the want of a ready and facile instrument for separating the lint from the seed was becoming severely felt. Picking by hand, which was the method in vogue, was a slow and costly process, a good worker not being able to clean more than 4 lb. of seed cotton, yielding about 1 lb. of fibre, per diem. The want being general, the attention of several indivi duals was directed to, and their efforts were engaged upon, the invention of some suitable mechanical appliance. As might be expected, several inventions were brought forward so nearly simultaneously that it is now difficult to award priority to the deserving one. Eve, Bull, and Whitney are competitors for the honour, and it is not easy to say which was first, or which invention was the most practically successful. Public opinion, however, seems to have decided that it is to Whitney that the world is indebted for the saw-gin.