The silk fibre, on the other hand, is a dual cylinder, spun by the worm in a continuous length, and with a perfectly smooth surface. Now, it would not be to our purpose to point out that in starting from a discontinuous simple fibre, to produce a continuous, therefore necessarily compound one, a very different treatment or process of spinning is required from that which the opposite condition renders practicable. We will rather consider the influence of structure upon materials manufactured from these fibres. It is obvious that the wool fibres, brought into contact with one another, tend to interlock; whereas silk fibres if rubbed or pressed together, simply slide over one another; the result in the fabric is by multiplication of the effect, a shrinking or contracting in length and breadth. This interaction of the fibres, and the phenomena to which it gives rise, is known as the felting of wool and woollen goods; this tendency, for the contrary reason, is not seen in silk fabrics. The production of paper from a disintegrated fibrous mass or pulp introduces similar considerations. That paper will be the stronger in which the constituent fibres are the better felted, and the degree in which felting takes place will depend to a great extent upon the form or microscopic peculiarities of the fibres. This is only one of the more obvious inferences to be drawn from the structure of fibres to the qualities of the papers which they compose. Other {32} equally important practical bearings will be seen to attach to the microscopic study of our fibrous raw materials, and to the consideration of this branch of the subject, we now ask the careful attention of the student.
Microscopical Examination.
It is impossible for us to deal specially with the subject of the microscope and its manipulation. The microscope, as a revealer of natural wonders is one thing; as an instrument of scientific discovery, quite another. For the latter, the student must train himself by systematic work, and should especially concentrate his attention upon some one branch of natural history, however restricted.
We shall assume, in our treatment of the subject, a knowledge of the microscope as an instrument of research, such as can be easily acquired in a few weeks of work under the guidance of a teacher or of one of the excellent manuals which now abound. We also assume a certain acquaintance with the elements of vegetable physiology, which it will be seen is necessary for a full grasp of the subject. Such an acquaintance, also, may be easily acquired, under direction, in a few weeks of work.
FIG. 2.
FIG. 3.
We have before alluded to the differences presented by {33} mono and dicotyledonous stems in regard to the distribution of their fibrous constituents. In illustration of this, we may cite Figs. 2, 3, which represent, (2) a section of the aloe, (3) a section of the jute plant. The available fibres are in (2) the fibro-vascular bundles (f), which are irregularly distributed throughout the main mass of cellular tissue, and {34} in (3) the bast fibres (f), which constitute a definite and separate tissue. We have already alluded to the practical consequences of this typical difference of distribution, in regard to processes of separating these fibres on the large scale.
This process we have explained is necessarily simpler in the case of a fibrous tissue, definitely localised; and this may be demonstrated by a superficial examination of a young branch of an exogen. As we know, the bark tissues are easily stripped from the underlying wood. If now we work up the former in a mortar, with a little water, we soon perceive the separation of the compound tissue into cellular matter on the one hand and fibres, the latter being more or less long and silky, according to the plant from which isolated. They vary in length from one millimetre to several centimetres, and are aggregated together in the plant in such a way as to constitute bundles, often of very considerable length; the general arrangement being comparable with that of the tiles in the roof of a house. It is important to distinguish the fibre-bundles from the elementary or normal fibres, and to this end they are designated by the term filament. Bast fibres are flexible and fusiform, terminating gradually in a point at either end, as represented in Fig. 4; bast filaments, built up of these fibres, containing often as many as twelve in the bundle, are usually cylindrical, but exhibit the widest differences in regard to the aggregation, in degree as well as number of their constituents. It is obvious that while the spinner has to do with these filaments, the paper maker works up the ultimate fibre constituents or fibres. It is also an obvious corollary from this distinction that a fibrous material which from “weakness” is unavailable for textile application, may yet be perfectly “strong” from the paper maker’s point of view; in other words, the individual fibres may be strong, but have little cohesion in the filaments. As we proceed, the student will see more and more the practical bearings of this branch of the study, and will perceive the inferences to be drawn from the investigation of {35} minute relationships to manufacturing processes and their products.