These projections, or serrations, which vary in number in different specimens of wool, are what it depends on for its felting properties. They are sharper and more numerous in felting wools than in others, and the better the felting properties of the wool, the more numerous the curls; because what induces curling on the animal's back leads to felting in the hands of the manufacturer. In felting, these projections catch one upon another, and occasion the hair to move in one direction, which is invariably root foremost, as we perceive on giving it a twirling motion between the finger and thumb; and it is only by the union of curve and serration, that felting can be accomplished certainly and perfectly.
Woolly fibre consists of a semitransparent stem, or stalk, supposed to be hollow, as represented at Fig. 4, Pl. V. and is partly distinguished from hair by the latter being opaque. Next to soundness, there are few qualities deserving of so much attention as softness, of which the ancient writers make frequent mention, and for the prevalence of which in our present wools fashion has done not a little. It is a quality that tends, in a material degree, to the cheap and easy working of the cloth, and, as such, is said to render wool 25 per cent. more valuable to the manufacturer than a harsh and brittle pile. It apparently depends on the fineness of the fibre, which should not, however, go the length of weakness. Fineness is in turn mainly connected with the yolk, the secretion of which ought, on that account, to be promoted by attention to the general management of the animal, as it is well known to undergo a change of properties by starvation, exposure, or any neglect whatever.
(32.) Particular soils injurious to Wool.—Soil, also, has much influence on the pliability of wool. Chalky lands, which are so notorious for injuring the fleece, are supposed to act in the manner of a corrosive, but the correct explanation is, not that the chalky particles attack the fibre in a direct way, but that they render it brittle, by absorbing the oily moisture with which it is naturally imbued. Moreover, the plants growing in such situations cannot but be injurious to sheep, owing to their impregnation, though a slight one, with calcareous matter; for grooms know well how soon a horse's coat becomes disordered by the frequent use of hard or well water, and prefer, therefore, the river for their steeds.[ [4]
(33.) Felting.—The felting of wool may be defined as a property depending on the curls and serrations of the fibre, by which it is allowed to move only with the root foremost, and by which it is enabled to catch and retain a hold on fibres that are near it, so as to form a web or cloth. Felting is best brought into operation by alternate pressure and relaxation, which may be produced in a variety of ways: the ancient method, and one still pursued by the Tartars, was to tramp on a mass or layer of moist unwrought wool, so as to form a coarse cloth or carpet; while the modern, and more perfect plan is, either, as in hat making, to apply pressure with the hands, or, as in the finishing of cloth, to pass the fabric repeatedly through rollers. The way in which a close fabric is formed, by the juxta-position of a few scattered hairs, gave rise for long, as well it might, to serious disputations among philosophers; and the favourite theories of each, unbased as they were on observation, might till now have agitated the scientific portion of our manufacturers, had not the microscope brought to light much of what is true and valuable in our researches.
Moisture appears to be of service during the felting of wool, as it induces it to curl, enabling the fibres to expand, and catch one on another, after they have been bent and compressed, by the force applied to them, and is of itself sufficient to felt a fabric, as we frequently perceive in the instance of stockings, which have been allowed to remain too long in water, when they become short from undergoing contraction, and resemble after such treatment an imperfect cloth. It is for this reason that the hatter, after tumbling over, in all directions, the fur of which the hat is to be made, wets it before applying pressure; and, that the woollen manufacturer, after freeing the web from grease, soaps it before its subjection to the action of the rollers.
Without felting, cloth would resemble a net, and would unravel on being cut, from the fibres crossing only in two directions; but the strokes of the mill put an end to this, by laying the fibres in every possible direction, and so twining them one with another, as to render them a coherent mass.
(34.) Different kinds of Wool.—The wool of this country is divided into two great classes—long and short: the former varies in length from three to eight inches, and before being made into stuffs and worsted goods, requires to be deprived of its felting tendencies, by passing it through heated iron combs, which remove the feathery parts, or serrations, and make it resemble silk or cotton.
The shorter combing wools are in general used for hose, and are softer than the long combing wools. Short wool is employed in the cloth manufacture, and is, on that account, frequently called clothing wool. It should approach in colour as much as possible to white, as a clear white ground is required for all cloths that are to be dyed bright colours, as well as for those dressed white: grey or black hairs injure the fleece very much, even though few and minute, as they give rise to reddish spots where the cloth is stoved. Herefordshire sheep are entirely free from this defect, and are, therefore, reckoned particularly valuable for clothing purposes.
(35.) Alterations induced by Crossing.—The breed exercises considerable influence on the wool, some sheep, as the merinos, being distinguished for the softness and beauty of the fleece; while others, as some of our small northern varieties, are famed for the very opposite characteristics.
According to the opinion on the continent, any race of ewes, however coarse and long in the fleece, will, on the fourth cross of the merino ram, give progeny with short wool equal to the Spanish. The truth of this proposition is however doubted, in a communication to the Board of Agriculture, by Dr Parry of Bath; but it is certain, he adds, that one cross more will in most cases effect the desired purpose. "If we suppose," he says, "the result of the admixture of the blood of the merino ram to be always in an exact arithmetical proportion, and state the native blood in the ewe as 64, then the first cross would give 32/64 of the merino, the second 48/64, the third 56/64, the fourth 60/64, the fifth 62/64, and so on. In other words, the first cross would leave 32 parts in 64, or half of the English quality; the second 16 parts, or one-fourth; the third 8 parts, or one-eighth; the fourth four parts, or one-sixteenth; the fifth 2 parts or one-thirty-second; the sixth 1 part, or one-sixty-fourth; and so on. Now, if the filament of the Wiltshire, or any other coarse wool, be in diameter double that of the Ryeland, it is obvious that, according to the above statement, it would require exactly one cross more to bring the hybrid wool of the former to the same fineness as that of the latter. This, I believe, very exactly corresponds with the fact. The difference between one-eighth and one-sixteenth is very considerable, and must certainly be easily perceived, both by a good microscope, and in the cloth which is manufactured from such wool. In the latter method, it certainly has been perceived; but I have had hitherto no opportunity of trying the difference by the former. The fifth cross, as I have before observed, brings the merino-Wilts wool to the same standard as the merino-Ryeland."