A number of substances contribute to the manufacture of paper; linen and cotton rags, hemp and various fibres are the most commonly used, not forgetting wood pulp which we shall mention in a moment. The finest and whitest paper is made from linen rags and that from unused linen and hemp is the strongest. Without attempting to describe in detail or even in outline the different processes which the various vegetable fibres must undergo before they appear in the guise of paper, we may say the treatment is very drastic. Strong chemicals and machinery designed to reduce the fibre to the finest possible particles render the examination of paper, for the purpose of discovering its composition, far from easy. Such fibres as survive the rough treatment are mere fragments yet they are often large enough for the lynx eyed microscope to read their story. Formerly the constituents of most papers could be separated into three classes according to their behaviour with iodine solution, but this test has been superseded by more complicated methods which do not concern us here.
The examination of various papers may prove interesting for example in linen rag paper, we ought to find some flax fibres, they will be sadly battered and torn but are usually recognisable under the microscope. Hemp paper is tough and is used for bank notes, in it some of the short tow fibres will probably occur and they will give a clue to its composition. Cotton rag paper is easily recognised for the fibres are very characteristic, a remark which also applies to jute paper, the so-called manila used for envelopes, wrappers, etc.
Mechanical wood pulp which enters so largely into the manufacture of paper is easily recognised by those who have given a fair amount of attention to the microscopical examination of plant life. Wood pulp is always used in conjunction with some binding material such as cotton or flax fibres. Many different kinds of wood are converted into pulp and of course it requires a considerable amount of experience to say exactly what kind of wood has been used in a certain paper. Some of the woods are poplars of various kinds, others spruces and firs. It is easy to distinguish the conifers as spruces and firs are called, for the reason that the trees bear cones. The little fragments of wood, scattered throughout the paper, have minute circular perforations upon them, resembling miniature quoits, if they belong to the conifers; none of the other woods possess these “pits” as they are called.
Very many other plant remains may be found in paper, for instance hop fibres are used sometimes and their presence is usually shown by remnants of the climbing hooks which, during life, studded the climbing stem of the hop.
Some of the important animal hairs, used in the manufacture of clothing, may now claim our attention. Wool and silk are of course the most important. The best wool is all obtained from the domestic sheep so let us examine one or two of the easily obtained hairs from this animal. As with the vegetable fibres we may examine them in a drop of water but, in this case, we shall find that we cannot make the water go near the wool for the reason that the latter is covered with a film of grease, called wool fat. Our first care, therefore, it to get rid of the wool fat and this may be done by shaking the specimen with a little ether or chloroform.
Having cleaned the wool fibres we may proceed to examine them under a high magnification and, to see their structure fully, we must move the fine adjustment to and fro, for it is not possible to obtain a true idea of its structure without doing so. We shall see that the hair consists of two layers, an outer skin and an inner core. The latter consists of a number of cells, whilst the former is composed of scales, of which the lower edges are arranged beneath the upper edges of the previous scales, like tiles on a roof. The free edges of the scales project outwards a little so that the wool, when not so highly magnified, appears to have a toothed margin. Further examination will show us that no single scale completely envelops the strand of wool, usually two scales make the complete circuit. It is a curious and easily tested phenomenon that in say an inch of wool from the same kind of sheep there are always the same number or very nearly the same number of scales. By counting the scales, experts can tell from what animal the wool is derived.
If we examine many samples of wool we shall not be long before we encounter certain specimens showing one or more constrictions. Now we all know that the reason why some people do not grow very much is because they are delicate, ill health affects the whole system. The constrictions in the sheep’s wool occur because the animal has suffered from some illness, or from great hunger or thirst, which has resulted in its wool not growing properly for a period corresponding to the duration of the illness or other calamity.
The examination of various animal hairs will help to while away many an hour and many of these objects are of the greatest interest. If we have the opportunity it will be interesting to compare the wool from different kinds of sheep, that from the Lincoln sheep, for example differs from that of shortwooled kinds. We may also compare goat’s wool with sheep’s, then there are differences between the hair of cows and calves. Comparisons always make microscopic work more interesting.
The microscopic examination of cloth, used for making our coats, is quite interesting work and withal important. A good deal of the cloth which is made up into suits is known as shoddy, that is to say that material that has been worn before; old rags of all sorts and many other extraordinary things go to the making of this cloth. There are special factories to which rags are sent to be made up into shoddy. One might think therefore that this substance would be easily recognised under the microscope but it is not quite so easy as we shall see. Absolutely pure wool from the sheep giving the best quality wool is only used in the very finest and most expensive fabrics. In a great deal of really good cloth we may recognise other hairs besides those of the sheep and sometimes vegetable fibres find their way into good cloth by accident. A piece of suspected cloth should be cut off and separated as far as possible into its different fibres. In shoddy we shall find few long fibres and they will all be much torn for the reason that the rags from which the material is made are cut up in the manufacture. If we find cotton fibres, we may be certain that our specimen is shoddy, also if we can find fibres of many different colours, though the final dyeing may have disguised the fact that the fibres have originally figured in fabrics of various colours.