When these defective fibrea are found in great abundance, they seriously detract from the work ing quality of the bulk; and it ia an important matter, in judging of cotton, to be able to dis tinguish them. This may be acquired by careful observation. In relation to these faulty fibrea, the greatest circumspection needa to be exercised, in the aeasons when the plant, with its load of bolla in all stages of growth, has been struck down by an early frost, for all the bolls are care fully gathered, and their contents abstracted, and mixed with the perfect lint.
The convolute form of the cotton fibre specially adapts it for ita manifold uses. If it were cylindrical, like the fibres of flax and hemp, its shortness would prevent its holding together. But from their peculiar form, when twisted in the process of spinning, the fibres become firmly interlocked, by which meana they may be made into a continuous thread, of considerable tenacity. When the finest varieties of cotton are employed, this thread is capable of remarkable attenuation. Lint gathered from the unopened or unripe pod, does not show these twistings in the fibre ; hence it is incapable, when spun into yarn, of affording the same cohesive power, and produces defects wherever it occurs. The convolutions in the dif ferent varieties of American cottons are more regular, uniform, and numerous than in those of other descriptions. and fully account for their acknowledged superiority. The naked eye is in capable of distinguishing these twists ; but the microscope shows them to amount to from one to tbree hundred an inch, and close examination would probably show even a wider range than this.
Many theoriea have been broached, and much ingenuity expended, in the attempt to explain the nature of this peculiarity of the cotton-fibre—the manner in which it is twisted upon its own axis. This point cannot be dilated upon here ; but it may be permitted to put forward very briefly
what appears to be a simple and natural explanation of the fact. It ia known that fibree taken from waive and unopened pods are invariably untwisted eylinders, tapering to a poiut at their extremity, which is closed. They have their root in, and receive all their nutrition from, the seed. Whilst in a growing state, the fluids of the plant circulate freely therein, conveying to every part the necessary amount of nutritive matter. When maturity is attained, this operation ceases : the juices are probably absorbed by the seed, and as they retire from the fibres, a vacuum is formed, first near the extremity, and subsequently along the length of each fibre, to its base at the junction with the seed. The pressure of the atmosphere, acting upon this vacuum where it is first formed, causes the tubc to collapse and twist, from its apex downwards to its base. The seeds of each pod, ripening simultaneously, set up a commotion in the interior of the latter, by the general collapse of their fibres ; and the consequent re-arrangement of these, in relation to each other, causes the pod to burst, when the desiccating action of the sun's rays expedites and completes the process. A further elucidation of this theory shows that it satisfactorily explains the whole phenomenon ; and though perhaps of no great practical utility, it is not without interest, as it appears to have engaged the attention, and to have baffled the penetration, of previous writers on the subject.