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.—Under the head of “Microscopic Features” we must include everything which has to do with the structure of the vegetable fibres, as well as their organisation and distribution in the plant. In the analysis of “organised” structures we employ the two methods. (1) of _dissection_; (2) _examination_ by means of the microscope; in other words, we first isolate the part under investigation by a mechanical process and then proceed to the optical resolution or analysis of the part. Having by analysis acquired a knowledge of the _parts_, we study their mutual relations in the structure they compose—we integrate our knowledge, so to speak—by means of sections of the structure, cut so as to preserve the cohesion of the parts in section, and yet in so fine a film as to appear under the microscope to be virtually a plane surface. These points are illustrated in the drawings given. 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.