the method of working up wool or hair into a kind of cloth or stuff, without either spinning or weaving it. In this country felting is little practised except in hat-making; and as nine-tenths of those who are employed in the manufacturing of hats know nothing of the principles on which they proceed, the following observations on the mechanism of felting must to them be both agreeable and useful. They are by M. Monge, and taken from the Annales de Chemie.

If we examine, in a microscope, human hair, wool, the hair of a rabbit, hare, beaver, &c. however great the magnifying power of the instrument may be, the surface of each hair appears perfectly smooth and even; or at least, if any inequalities are to be perceived, they seem rather to arise from some difference in the colour and transparency of particular parts of these substances than from the irregularity of their surfaces; for their image, when viewed by a solar microscope, is terminated by even lines, without any roughness. The surface of these objects, however, is by no means smooth; on the contrary, it appears to be formed either of lamellae which cover each other from the root to the point, pretty much in the same manner as the scales of a fish cover the animal from the head to the tail; or, more probably, of zones placed one over the other, like what is observed in the structure of horns: to this conformation it is, that the substances here treated of owe their disposition to what is called felting.

If, with one hand, we take hold of a hair by the root, and draw it between two fingers of the other, from the root towards the point, we are hardly sensible of any friction or resistance, nor can we distinguish any sound; but if, on the contrary, we hold the hair at the point, and draw it between the fingers, from the point towards the root, we are sensible of a resistance which did not exist in the former case; a sort of tremulous motion is likewise produced, which is not only perceptible to the touch, but may also be distinguished by the ear.

It is evident therefore, that the texture of the surface of a hair is not the same from the root towards the point as from the point towards the root; and that a hair, when grasped, must offer more resistance in sliding or moving progressively towards the point than towards the root; i.e., in moving with its point foremost.

If a hair, after being taken hold of by the forefinger and thumb, be rubbed by them, in the longitudinal direction of the hair, a progressive motion takes place, and this motion is always towards the root. This effect does not at all depend on the nature of the skin of the fingers or its texture; for if the hair be turned, so that the point is placed where the root was, the movement then becomes contrary to what it was before; that is to say, it is always directed towards the root.

What is observed, in the above instance, is entirely analogous to what happens when country children, by way of sport, introduce an ear of rye or barley between the wrist and the shirt, the points of the beards of which are directed outwards. By the various motions of the arm, this ear, sometimes catching against the shirt, sometimes against the skin, takes a progressive motion backwards, and soon gets up to the arm-pit. It is very clear that this effect is produced by the beards of the ear, and indeed chiefly by the apertures upon those beards; which, being all directed towards the point, do not permit the ear to move in any other direction than towards that part to which it was united to the stalk. There is no doubt that it is the same with respect to hair; and that its surface is beset with apertures, which, being laid one upon the other, and turned towards the points, permit no motion but towards the root.

A tight knot, made in the middle of a hair, is very difficult to untie by the usual means, on account of the extreme thinness of the hair; but if we place the hair in the bend of the hand, so that the knot is in a line with the little finger, and, after grasping the hair by clasping the hand, we strike the fit several times against the knee, the apertures of one end of the hair being now in a contrary direction to those of the other, each of the ends recedes a little, one of them one way, the other the contrary way; the knot is thereby opened, and, by introducing a pin into the eye which is formed, it is very easy to finish untying it.

These observations, which it would be useless to multiply, relate to long hair, that having been taken as an example; but they apply with equal propriety to wool, fur, Furs, and in general to every kind of animal hair. The surface of all these is therefore to be considered as composed of hard lamellae placed one upon another, like tiles, from the root to the point; which lamellae allow the progressive motion of the hair towards the root, but prevent a similar motion towards the point.

From what has been said, it is easy to explain why the contact of woollen stuffs is rough to the skin, while that of linen or cotton cloths is smooth; the reason is, the asperities upon the surface of the fibres of the wool (notwithstanding the flexibility of each particular fibre), by fixing themselves in the skin, produce a disagreeable sensation, at least till we are accustomed to it; whereas the surface of the fibres of hemp or flax, of which linen is made, being perfectly smooth, do not cause any such sensation. It is also evident, that the injury arising to wounds or sores, from the application of wool, does not proceed from any chemical property, but is occasioned solely by the conformation of the surface of the fibres; the asperities of which attach themselves to the raw and exposed flesh, which they stimulate and irritate to such a degree as to produce inflammation.

This conformation is the principal cause of that disposition to what is called felting, which the hair of all animals in general possesses.

The hatter, by striking the wool with the string of his bow (see Hat, Engels.), separates the hairs from each other, and causes them to spring up in the air; the hairs fall again on the table, in all possible directions, so as to form a layer of a certain thickness, and the workman covers them with a cloth, which he presses with his hands, moving them backwards and forwards in various directions. This pressure brings the hairs against each other, and multiplies their points of contact; the agitation of them gives to each hair a progressive motion towards the root; by means of this motion the hairs are twisted together, and the lamellae of each hair, by fixing themselves to those of other hairs which happen to be directed the contrary way, keep the whole in that compact state which the pressure makes it acquire. In proportion as the mass becomes compact, the pressure of the hands should be increased; not only to make it more close, but also to keep up the progressive motion and twisting of the hairs, which then takes place with greater difficulty; but throughout the whole of this operation, the hairs fix themselves only to each other, and not to the cloth with which they are covered, the fibres of which, as we have already said, are smooth, and have not that disposition to felt which we have described above.

It may not be amiss here to explain why that hair which is intended for making hats is always cut off with a sharp instrument (although that cannot be done without losing a part of its length), and not plucked out by the roots, as might be done after softening the skin: the reason is, the bulb of the hair, which in the latter case would come out with it, would render that end which was fixed in the skin thick and obtuse; and it would consequently be less disposed to introduce itself among the contiguous hairs, and to contribute by its progressive motion to the contexture of the mass.

The above described conformation of the surface of hairs and wool is not the only cause which produces their disposition to felting. It is not sufficient that every hair possesses the forementioned tendency to move progressively towards the root, and that the inclined lamellae, by hooking themselves to each other, preserve the rigid mass in that state to which compression has brought it; but it is also necessary that the hairs should not be straight, like needles; if they were so, pressing and rubbing them together would merely cause them to continue their progressive motion, without changing their direction; and the effect of those operations would only be to make them move from the centre of the mass, without producing any compactness in it. Every hair must therefore be twisted or curled in such a manner that the extremity which is towards the root may be disposed to change its direction perpetually, to twist itself about other hairs, and to incline towards itself again, in case it should be determined thereto by any change in the position of the rest of its length. It is because wool has naturally this crooked form that it is so proper for felting, and that it may be made use of for that purpose without undergoing any previous preparation.

But the hairs of the beaver, the rabbit, the hare, &c., being naturally straight, cannot be employed alone in felting till they have undergone a preliminary operation; which consists in rubbing or combing them, before they are taken off the skin, with a brush dipped in a solution of mercury in aquafortis (nitric acid). This liquor, acting only on one side of the substance of the hairs, changes their direction from a right line, and gives them that disposition to felting which wool naturally possesses.

When the hairs are not intended to enter into the body of the mass, but are only to be employed in making a sort of external coating, such as is sometimes given to the outer surface of hats, the operation just mentioned need not be performed; but the felt on which they are to be fixed being finished, the hair is uniformly spread upon the surface to which the coating is to be applied; and, being covered with a cloth, it is pressed with the hands, and agitated for a certain time. By these means, the hairs introduce themselves, by the root, a certain depth into the felt, and are there fixed by their lamellae in such a manner as not to be easily extracted. A particular direction is afterwards given to them by means of a brush, and they are made to keep this direction by having a hot iron passed over them. If the agitation were continued for a longer time, the hairs, not having their straightness destroyed by the operation before described, would pass entirely through the felt, going out at the opposite surface, as each hair follows exactly the direction it acquired at the beginning.

It is owing to the very same circumstances which make wool and hair capable of felting, that woollen cloth is thickened by felting. See Felling in this Supplement.