He was a big, powerful man, the sort of man generally described as a 'typical guardsman.'

He had wandered much. He had seen men work at many occupations tea planters in Ceylon and China, gold miners on the Rand, diamond miners at Kimberley, cowboys in the Wild West, lumberjacks in Canada. . . . He had seen men build ships and make cotton and woolen goods, and he had sailed in a tramp steamer. He had soldiered through the war and risen to the rank of colonel; but he confessed he had never seen an electrically driven coalcutting machine working in a twentyinch seam.

He was anxious to see one. Our manager granted permission, and he came to see. I met him at the pit-head. He was dressed for the occasion in a suit of mechanic's overalls. With eighteen others we got into the cage.

From the Daily Herald (London Labor daily), May 3

As the descent began he gasped for breath and clutched my arm.

The cage stopped, and we stepped out. A few minutes were spent explaining the mysteries of haulage ropes and roadways; then we started for the face. 'Now keep your back well bent; it's only four feet high, so be careful!'

We tramped steadily. He stumbled; his eyes were unaccustomed to the faint light of a safety lamp. 'Ugh; wait a minute! Ugh, my head!' He failed to keep his head low enough, and hit a baulk. I turned round. The perspiration was streaming down his face, his breathing was labored, and we had only gone four hundred yards. We halted a few minutes; I warned him to stoop lower, and away we went again.

At last we arrived at the deputy's place, and I handed him a pair of leather knee-pads. 'What are these for?' he asked. I fixed them for him, explaining that they were to protect his knees when creeping. 'Are we going to creep?'

'Yes.' 'Ugh! Is it far?' 'No; keep your back well down and follow me.'

'Here we are. That's the face. Now get down, and we'll crawl along to where the coal-cutter is working.'

With great difficulty he got into the twenty-inch-high passage, and we dragged ourselves along. Men were working stripped to the waist and bathed in perspiration. One stopped the machine and explained how it worked. We pulled ourselves back a little. 'Right; set her away!' The power was switched on, and the machine began working.

Flying coal dust filled the air till you could not see. The stench of heating oil and the sweat of human bodies made it almost impossible to breathe. The Colonel coughed and spluttered as the coal dust got into his throat. The roof 'weighed,' the supports creaked, the coal cracked like rolls of thunder.

The scene was indescribable. We half crawled, half dragged ourselves

along. 'Let's get out of this,' pleaded our visitor. So out we got, back to the deputy's 'kist,' offed with our kneepads, and made our way to the shaft. The visitor reeled like a drunken man. His head hit the roof. Down went his head and up went his back. 'Ugh!' and he fell on his knees. Out went his lamp. One lamp between two of us. After many stops we arrived at the shaft, and then up into the fresh air. With great difficulty he stretched himself erect. His back ached, his head ached, his knees ached, he felt awful. 'Oh, is n't the fresh air grand?' he cried.

I asked him what he thought of it all. His answer came like a burst of thunder: 'It's like Hell! Absolutely the rottenest job I ever saw. I am sorry for those fellows. I wonder they stick it. Fancy sticking a job like that for ten shillings a day! It's a rotten job. Absolutely rotten!'

I don't think he'll want to see a coalcutting machine at work in a twentyinch seam any more for a while.

No other substance is receiving so much attention from the physical chemist today as cellulose. This is not only the chief structural material in all plants, but it is also the raw material of new and important industries. Notwithstanding the patient study that has been devoted to it, however, its chemical structure and composition still present many puzzles.

Cellulose has two qualities that render the investigation of its physical and chemical constitution especially difficult: it is insoluble in water or other ordinary solvents, and it is extremely sensitive to the action of acids and saline solutions. These qualities make it almost impossible to determine from the products of its decomposition what the form of its original constituents was. To be sure, cellulose shares this incapacity for molecular dispersion with several other organic substances, like albumin, starch, and certain pigments, which are classified together under the collective name of colloids.

The first investigator whose patient studies gave him some insight into the spacial structure of the colloids and their so-called solutions was Karl von Nägeli, whose researches into the constitution of starch in the late fifties of the last century convinced him that all colloids were made up of minute crystalloid bodies which he called micellæ, or 'little crumbs.' These he assumed to be extremely diminutive groups of molecules, too small to be visible under

1 From Kölnische Zeitung (Conservative daily), April 22

the most powerful microscope, arranged in symmetrical patterns so that their internal structure resembled that of crystals, although they might assume various outward shapes. While most chemical substances, like salt, sugar, and the like, separate into their individual molecules in water, the colloids cannot do this, but simply separate into these tiny molecular aggregations, or micellæ, which are the lowest subdivisions of which they are capable while retaining their collodial identity.

Nägeli's researches, however, could be pursued only to a certain point for lack of the technical instrumentalities necessary for further investigation. The next advance had to wait upon later discoveries, and only within the past few years has the nature of these molecular groups, or primary particles, of the cellulose structure been fully established. The first step forward followed the discovery that cellulose refracted light in the same way that crystals do- for instance, the cell walls of a flax fibre produced a refraction six times that produced by quartz. It was shown further, by saturating the cellulose with water, that this double refraction was not due to the fact that the tiny rod-groups, or micellæ, were embedded in a medium of different refractivity from itself, but that the micelle themselves had a distinct refractive index, such as had hitherto been assumed to be peculiar to microscopic crystals.

This led to the conclusion that cellulose must consist of minute rodlike

crystals connected in series, and that this stringing together of the minute rods, and the parallel grouping of the strings, persisted even throughout a great number of chemical changes in the cellulose itself. For example, the rodlike structure of the micelle was not affected when cellulose was treated with nitric acid and thus converted into guncotton.

These conclusions were brilliantly confirmed when the X-ray was applied to the investigation of fibres. In 1920 ramie, an almost pure form of cellulose, was discovered to produce an X-ray photograph of a kind previously observed only in case of crystals. For example, while noncrystallized, or socalled amorphous, substances produce simply a black blur on a Röntgen plate, crystals and crystalline bodies produce a number of alternating bright and dark curved lines called interference lines. The appearance and strength of these lines bear an intimate relation to the inner structure of the crystal- the so-called crystal grating. In case of ramie fibres, these interference rings were not, to be sure, complete, but fell into definite symmetrically arranged points or short segments of circles. Polanyi, who in 1921 made an exhaustive investigation of these Röntgen, four-point patterns, or fibre diagrams, showed that they appear only when the innumerable tiny crystals that form a crystalline substance all lie with their axes in the same direction, instead of in different directions. Such an arrangement of these crystalloids in parallels is characteristic of the structure of all fibres not only of ramie, but cotton, silk, wood fibre, and all similar substances of vegetable or animal origin, including hair, muscles, and

nerves.

But while natural cellulose in the form of ramie, cotton, flax, and other similar fibres, has all its crystallized

micellæ lying with their axes parallel to the axis of the fibre itself, that is not true of artificial cellulose, mercerized cotton, and most kinds of artificial silk. The latter have their crystals lying pell-mell in all directions, and an X-ray photograph of them shows alternating dark and light lines in closed circles.

Very recently it has proved possible, by employing certain methods of drawing and tension when the cellulose is leaving the copper-ammoniac solution, to produce an artificial silk whose crystalline structure as shown by its X-ray photograph is the same as that of natural cellulose. In other words, its rodlike, crystalloid micellæ all have their axes lying in the same direction. The displacement, or jumbling-up out of their normal parallel order, of the crystals in ordinary artificial silk explains why this substance reacts so much more readily to chemicals, and absorbs water and colors so much more quickly, than natural fibres. Its component crystals lie in all directions, leaving interstices and exposing a larger surface to foreign ingredients like pigments and moisture. On the other hand, the end-to-end arrangement of the micellæ in parallel lines that exists in natural fibres is easy to understand, for it is necessary, not only for the upward growth of the plant, but in order to give the plant greater resistance to wind, weather, and other external influences.

While the origin of the crystalloid structures now assumed to make up every fibre is not definitely known, it is very probable that they do not exist in the young plant or animal from the beginning, but are developed from an amorphous jelly. Young asparagus, for example, and the chitin of insects in the chrysalis state, are still structureless, and consist of an incompact, watery substance that is later converted

into a firm crystalline composition. We may infer that drawing and tension play the same part in the formation of the fibre here that they do in the latest processes of producing artificial 2 silk. Drawn-metal wire, which likewise consists of minute crystalline rods and consequently produces the same Röntgen diagrams as natural cellulose, gives us a hint to this effect, and confirms the inference that vegetable fibres are crystallized from some amorphous material.

This assumption has been strengthened by the results of recent investigations in natural silk-fibrine and chitin, which play the same part in the animal structure that cellulose does in the vegetable structure. In all these different organic compounds, both vegetable and animal, an identical crystalline substance has been discovered embedded in certain adhesive materials which chemists have for a long time designated as mucilages, or semicellulose, without knowing their exact constitution. Unless there were some such intermediate substance, cellulose itself would not possess sufficient resistance to wind-pressure and similar forces to perform its functions in plant and animal existence. For if the tiny crystalline rods were in direct contact, their size and shape would be easily modified by external accident and the strength of the cellulose fibre would be seriously weakened.

This binder or cement in cellulose is much more easily attacked by chemicals than the crystals themselves. Every laundryman knows how quickly textile fibres are affected by mineral acids, which weaken them so that they will rub to pieces between the fingers. Chemists have hitherto called the product resulting from the action of such acids upon cellulose hydrocellulose, without being able to describe exactly what the chemical reaction

producing it was. Investigations show that this product consists mostly of unchanged or very slightly changed cellulose. X-ray photographs show that hydrocellulose has practically the same Röntgen diagram as ordinary cellulose. We are thus led to infer that acids do not affect the tiny crystalline rods or micellæ themselves, but only the binder between them, and that their effect is simply to allow these rods to fall apart.

This isolation of the crystalline bodies is important in its bearing upon other chemical transformations. We have already mentioned that when cotton is converted into guncotton, or nitrocellulose, the outer form of the fibres is not changed. All that occurs is an internal transformation, or pseudomorphosis, of the tiny crystalloids. That is, the chemical reaction occurs in each of these crystalloids individually, while it is kept in its original position by the binding substance. Very recent researches show that when cellulose absorbs water the latter is taken up by the binder between the micellæ, and not by the crystalloids themselves.

What we have said of the structural character of fibres, as consisting of minute micellæ, or rodlike crystalloids arranged parallel and end-to-end, which we can now assume to have been definitely demonstrated by the X-ray, fully explains two characteristics which distinguish cellulose from other organic substances its tensile strength and its chemical inertness. But when we extend our inquiries to the ultimate component of these crystalloid formations, to the primary parts of the micella, we immediately encounter new difficulties which have not yet been solved. We are practically certain that the ultimate constituents of the micella must be a grape-sugar residuum consisting of six atoms of carbon, ten atoms of hydrogen, and five atoms of oxygen. The presence of these grape-sugar or