degree of that peculiar property of interlocking of the hairs known as felting. Let us now again look at a human hair. The light was reflected from this hair as it lay under the microscope, and now we see the reason of the saw-like edge in the longitudinal section, for just as the tiles lie on the roof of a house, or the scales on the back of a fish, so the whole surface of the hair is externally coated with a firmly adhering layer of flat overlying scales, with not very even upper edges, as you see. The upper or free edges of these scales are all directed towards the end of the hair, and away from the root. But when you look at a hair in its natural state you cannot see these scales, so flat do they lie on the hair-shaft. What you see are only irregular transverse lines across it. Now I come to a matter of great importance, as will later on appear in connection with means for promoting felting properties. If a hair such as described, with the scales lying flat on the shaft, be treated with certain substances or reagents which act upon and dissolve, or decompose or disintegrate its parts, then the free edges of these scales rise up, they "set their backs up," so to say. They, in fact, stand off like the scales of a fir-cone, and at length act like the fir-cone in ripening, at last becoming entirely loose. As regards wool and fur, these scales are of the utmost importance, for very marked differences exist even in the wool of a single sheep, or the fur of a single hare. It is the duty of the wool-sorter to distinguish and separate the various qualities in each fleece, and of the furrier to do the same in the case of each fur. In short, upon the nature and arrangement and conformation of the scales on the hair-shafts, especially as regards those free upper edges, depends the distinction of the value of many classes of wool and fur. These scales vary both as to nature and arrangement in the case of the hairs of different animals, so that by the aid of the microscope we have often a means of determining from what kind of animal the hair has been derived. It is on the nature of this outside scaly covering of the shaft, and in the manner of attachment of these scaly plates, that the true distinction between wool and hair rests. The principal epidermal characteristic of a true wool is the capacity of its fibres to felt or mat together. This arises from the greater looseness of

Fig. 9.

the scaly covering of the hair, so that when opposing hairs come into contact, the scales interlock (see Fig. 9), and thus the fibres are held together. Just as with hair, the scales of which have their free edges pointing upwards away from the root, and towards the extremity of the hair, so with wool. When the wool is on the back of the sheep, the scales of the woolly hair all point in the same direction, so that while maintained in that attitude the individual hairs slide over one another, and do not tend to felt or mat; if they did, woe betide the animal. The fact of the peculiar serrated, scaly structure of hair and wool is easily proved by working a hair between the fingers. If, for instance, a human hair be placed between finger and thumb, and gently rubbed by the alternate motion of finger and thumb together, it will then invariably move in the direction of the root, quite independently of the will of the person performing the test. A glance at the form of the typical wool fibres shown (see Fig. 10),

Fig. 10.
Finest merino wool fibre. Typical wool fibre. Fibre of wool from Chinese sheep.

will show the considerable difference between a wool and a hair fibre. You will observe that the scales of the wool fibre are rather pointed than rounded at their free edges, and that at intervals we have a kind of composite and jagged-edged funnels, fitting into each other, and thus making up the covering of the cylindrical portion of the fibre. The sharpened, jagged edges enable these scales more easily to get under the opposing scales, and to penetrate inwards and downwards according to the pressure exerted. The free edges of the scales of wool are much longer and deeper than in the case of hair. In hair the overlapping scales are attached to the under layer up to the edges of those scales, and at this extremity can only be detached by the use of certain reagents. But this is not so with wool, for here the ends of the scales are, for nearly two-thirds of their length, free, and are, moreover, partially turned outwards. One of the fibres shown in Fig. 10 is that of the merino sheep, and is one of the most valuable and beautiful wools grown. There you have the type of a fibre best suited for textile purposes, and the more closely different hairs approach this, the more suitable and valuable they become for those purposes, and vice versâ. With regard to the curly structure of wool, which increases the matting tendency, though the true cause of this curl is not known, there appears to be a close relationship between the tendency to curl, the fineness of the fibre, and the number of scales per linear inch upon the surface. With regard to hair and fur, I have already shown that serrated fibres are not specially peculiar to sheep, but are much more widely diffused. Most of the higher members of the mammalia family possess a hairy covering of some sort, and in by far the larger number is found a tendency to produce an undergrowth of fine woolly fibre, especially in the winter time. The differences of human hair and hairs generally, from the higher to the lower forms of mammalia, consist only in variations of size and arrangement as regards the cells composing the different parts of the fibre, as well as in a greater or less development of the scales on the covering or external hair surface. Thus, under the microscope, the wool and hairs of various animals, as also even hairs from different parts of the same animal, show a great variety of structure, development, and appearance.

We have already observed that hair, if needed for felting, is all the better—provided, of course, no injury is done to the fibre itself—for some treatment, by which the scales otherwise lying flatter on the hair-shafts than in the case of the hairs of wool, are made to stand up somewhat, extending outwards their free edges. This brings me to the consideration of a practice pursued by furriers for this purpose, and known as the sécretage or "carrotting" process; it consists in a treatment with a solution of mercuric nitrate in nitric acid, in order to improve the felting qualities of the fur. This acid mixture is brushed on to the fur, which is cut from the skin by a suitable sharp cutting or shearing machine. A Manchester furrier, who gave me specimens of some fur untreated by the process, and also some of the same fur that had been treated, informed me that others of his line of business use more mercury than he does, i.e. leave less free nitric acid in their mixture; but he prefers his own method, and thinks it answers best for the promotion of felting. The treated fur he gave me was turned yellow with the nitric acid, in parts brown, and here and there the hairs were slightly matted with the acid. In my opinion the fur must suffer from such unequal treatment with such strong acid, and in the final process of finishing I should not be surprised if difficulty were found in getting a high