in science allow us now to answer this question with confidence. They have, from several different directions, con. tributed towards establishing the atomic hypothesis in a position of unassailable strength, and have furnished a proof of the real and actual existence of atoms or discrete particles as constituting the fundamental basis of matter. Only a few of these proofs can be indicated here, but a clear account of the evidence accumulated in support of the real existence of discrete particles has recently been published by one whose work has greatly advanced our knowledge of this subject ("Atoms," by Jean Perrin).

The phenomena of diffusion, more especially in gases, led to the conclusion that the particles or molecules of which matter was assumed to be constituted are not in a state of rest. In the case of a gas, these molecules are regarded as being in a state of constant and tumultuous commotion, which is not entirely subdued even when the gas is condensed to the liquid, or frozen to the solid state. That, at least, is the picture of matter which presented itself to the inner vision of a genius like Clerk Maxwell, and which forms the basis of what is known as the kinetic theory, a theory which was developed by applying to these still hypothetical molecules the general laws of mechanics. In this way it became possible, on the basis of experimental data, to calculate not only the absolute mass of the molecule-the hydrogen molecule weighs about three quadrillionths (million million million millionths) of a gramme-but also its dimensions (approximately one hundred millionth of an inch in diameter), and the speed of its movement (several hundred yards per second); and the agreement between the values derived from the different kinds of measurement cannot but excite our admiration. And yet the theory cannot carry complete conviction, by reason of the number of hypotheses which it involves; and s there have not been wanting some who refused to accept the objective reality of molecules. And yet, even in 1827, these molecules had, all unknown to their observers, made their presence manifest by the effects which they produced. In that year the botanist, Brown, observed that when suspensions of pollen grains were examined under the microscope the particles were seen to be in rapid motion, vibrating, rotating, moving along a zigzag path, sinking, rising-perpetually in motion. In this so-called Brownian movement-observed long ago by Buffon and Spallanzani, who saw in it a manifestation of lite-we see, not, it is true, the molecules themselves, but the effects of the incessant bombardment of the coarser particles of the suspension by the molecules of the liquid. When one applies to the suspension the law of the equi partition of energy, it follows that, in a condition of equilibrium, the kinetic energy of the relatively coarse particles will be the same as that of the molecules of the liquid. We have, then, in the Brownian movement merely a magnified picture, as it were, nf molecular movement; and if this is so, then the magnitudes calculated from these comparatively coarse suspensions should be the same as those calculated according to the molecular kinetic hypothesis. This conclusion has been tested in various ways, more especially by the French physicist, Jean Perrin, and has been found to be correct.

As a result of the combined action of gravity and of the kinetic energy of the molecules, the molecules in a column of gas are more crowded together at the bottom of the column than at the top, in accordance with the law that when the distances from the bottom increase in arithmetical progression the concentration of the particles diminishes in geometrical progression. By counting the number of particles at different levels of a column of a fine suspension of gamboge in water, Perrin found that the distribution of the particles accurately obeyed the same law. These particles in Brownian movement, therefore, behave exactly as the molecules of a gas would behave according to the kinetic theory; and in a number of other ways also the suspensions of particles which can be seen behave in exact concordance with the laws which have been deduced for invisible particles. Our belief in the actual

9

existence of these particles is thereby greatly strengthened. The extension of our limits of vision, also, which the invention of the ultramicroscope has made possible, has disclosed the existence of particles in what hitherto bad appeared, even under the most powerful magnification, to be homogeneous matter; and by this means particles not greatly exceeding in dimensions those of the molecules have been detected. The smaller the particles the more lively is their motion, so that we can scarcely hesitate to believe that in the rapid, darting motions of the ultramicroscopic particles we have made manifest to us something of the extraordinary stir and commotion which is going on in that world of molecules which is beyond the power of our direct observation.

But the grained or discontinuous structure of matter has been still more clearly demonstrated in the recent striking work on radio-activity. The phosphorescent light emitted by certain materials, when bombarded by the a rays emitted by radio-active substances was found by Sir William Crookes to be resolved, when examined by a magnifying glass, into separate scintillations or points of light, each of the star-like points of light marking the impact of a projectile; and in the spinthariscope, invented by Sir William Crookes, one is enabled to see the individual effect of a single atom. But these a-rays, as Sir Ernest Rutherford most definitely has shown, are positively charged atoms of helium, which he has even succeeded in counting, and the atomic structure of this gas is thereby demonstrated.

Whether we calculate the fundamental molecular magnitudes from the viscos ty of gases; from the Brownian movement of fine, but visible particles; from the phenomena of radio-activity; or from the blue colour of the sky, by which also the discontinuous structure of matter is made manifest, the same results are obtained, and the real existence of molecules is thereby established with a probability amounting to a certainty. But while we can regard the atomic constitution of matter as established beyond any reasonat le doubt, yet, in the words of Prof. Perrin: "Atoms are no longer eternal indivisible entities, setting a limit to the possible by their irreducible simplicity; inconceivably minute though they be, we are beginning to see in them a vast host of new worlds. . . Nature reveals the same wide grandeur in the atom and the nebula, and each new aid to knowledge shows her vaster and more diverse, more fruitful and more unexpected, and, above all, unfathomably immense." - The New Statesman, June 16, 1917.

NITROGEN FROM THE AIR. MANCHESTER'S NEW ENTERPRISE.

WE are able to supplement from a well-informed source the interesting announcement in the Manchester Guardian of June 23 that plant is about to be erected in Manchester for the manutacture of nitrogenous products from the nitrogen in the air. For reasons that will be obvious, fuller details must be reserved until the conclusion of the

war.

Ever since the British blockade was enforced, Germany has found it impossible to import Chilian nitrates for the manufacture of explosives and fertilisers. It reverted, therefore, to the expedient of "fixing" the nitrogen from the air, and has adopted it to a huge extent since almost the beginning of the war. It has been stated in German technical journals that the output of nitrogenous products by the Bädische-Anilin Fabrik, with the aid chie fly of the Haber-catalytic process, amounts now to about 500,000 tons a year. By these means the Germans get all the nitrogenous ingredients for their high explosives.

Attempts have been made to work the Haber process in this country, but all have failed, and the general consensus of opinion now is that this is not a commercial process, as

the expense and risk appear to be enormous. Germans, however, it is a case of needs must.

The only other way by which nitrogen can be fixed from the air is by the electric processes, of which up to now the principal have been the Baekeland and Evde, the Schönhurr, and the Pauling. All of these are single-phase and electrical processes, and are considered workable commercially only in places like Norway, where electricity can be generated cheaply by water power. None of them has been worked in England, because of the high cost of electricity here, which makes them uneconomic under ordinary conditions.

The consequence is that the fixation of atmospheric nitrogen has not been adopted in this country, which relies for its supplies of this valuable ingredient of high explosives and an indispensable part of all the principal fertilisers on the utilisation of Chilian nitrates, the price of which has increased enormously since the beginning of the

war.

A New Process: English Discovery.

A new factor in the situation has now arisen in the new method of nitrogen fixation from the air which is about to be started in Manchester. National considerations preclude details being given at present, but it is believed that with this process nitrogen can be "fixed" anywhere in England at a very low cost, even where electricity is fairly expensive, because it apparently achieves the highest efficiency of nitrogen fixation per kilowatt hour of energy used that has ever been achieved or even dreamt of by any of the other processes mentioned. Its inventor is a British subject.

The Manchester Corporation succeeded in being the first to get the industry started, because it went out of its way to help the promoters, the International Nitrogen and Power Company, 8, Waterloo Place, London, who hold the exclusive rights to work the process in Great Britain. The new industry is believed to have great possibilities, not only for war purposes but after the war. Possibly when the method comes to be worked throughout the United Kingdom it will make this country independent of oversea supplies of fixed organic nitrogen, and provide a new security against the danger of interruption of oversea supplies of essential ingredients of explosives in time of war. If it can be done the whole of our nitric acid supplies could be obtained in this way, and also picric acid, an essential ingredient in synthetic dyes.

Above all, it would bring to realisation Sir William Crookes's prediction to the British Association at Bristol over thirty years ago that the future of the white race would largely depend on the economic fixation of atmospheric nitrogen, by which the world might be made to yield larger quantities of wheat and other foodstuffs.

Through the good offices of the Manchester Corpora tion an excellent site for the works has been provided. Construction has already begun, and the establishment should be working within six months from now.

There is no special virtue in the air of Manchester that has led to the selection of the city for this important pioneer enterprise. The choice was determined by other circumstances. Nor need the public have the least apprehension of the effects of the process on atmospheric conditions. The volume of air used up is an infinitesimal fraction of the aerial ocean.

Inquiries made recently by a representative of the Man chester Guardian showed that a movement for carrying into effect a project for obtaining nitrates from the atmos phere was started in Manchester ten or twelve years ago, the motive being, of course, mainly a commercial one. The promoters were, for the most part, engaged in the bleaching industry, who desired to avoid, if it was possible, the expense of bringing nitrates so largely used in their business from South America. It was found, however, that an obstacle to the development of that scheme was the intense heat required to make the process successful. "We needed heat," one of the promoters of that time said recently, "of an intensity of 2000°, and the result was

A chemist at a large house in the dyeing trade expressed the view recently that but for the fact that the Germans had for years obtained nitrates from the air the war would have been over long ago, considering the present diffi culties in the way of their obtaining them from Chili or other South American sources.

MAKING ANIMALS TRANSPARENT. WHAT THE ROYAL COLLEGE OF SURGEONS HAS TO SAY TO THE SPALTEHOLZ MEthod.

(From a Correspondent).

IN the CHEMICAL NEWS of June 13 appeared an account of the Spalteholz method of making animals transparent, as exemplified in successful specimens exhibited to a CHEMICAL NEWS representative by Dr. S. F. Harmer, F.R.S., at the Natural History Museum, South Kensington. When Dr. Harmer applied to the Patents Court for licence to employ this method, which is covered by a German patent, the Controller of Patents, Mr. Temple Franks, threw doubt on the validity of the patent because, apparently, it seeks to patent a principle of optics by basing the method on the refraction of light. The dead animal, after chemical treatment, is placed in a solution having tho same index of refraction as its own tissues. Skeleton, muscles, and arteries are then revealed through the fabric of the outer tissues.

At the Royal College of Surgeons, however, doubt is cast on the subject matter of the patent from another point of view-that fruitful source of contention known, in the term of the lawyers, as prior user! In a word, there is nothing new in the method at all! They have used it at the Royal College of Surgeons for years!

Prof. Keith (who sat with the imposing skeleton of the Irish giant O'Bryne behind him-an eighteenth century worthy who looked out on the world from the unusual altitude of 8ft. 4in.) assured the CHEMICAL NEWS interviewer that the idea of clarifying tissues was as old as the hills. Instead of applying the process to a small piece of tissue Spalteholz had used it for large bodies-" a thing none of us have wanted to do particularly," said Dr. Keith, "because we don't see much use in it. It has long been used in microcopy. Indeed, the principle of the employment of clarifying oils is tolerably obvious. You go into a wooden building, in the daylight, and you see the sun shining through a resinous knot-and there you are, the whole thing is complete! The rat, by this process, is transparent, instead of the knot, because of an essential oil.

"But Spalteholz cannot claim to have invented transparencies, even of animals. Thoy were first made in the fifties by Prof. Beale, of King's College, in the Strand. Beale used as alkali-potassium hydrate will servethongh Beale never patented his method. He was too busy with other things. Beale's method was afterwards re-discovered on the Continent, where it came to be known as Schultze's method. We have employed Beale's method in the College for the last fifty or sixty years, and have several specimens in the museum.