which is not being applied in this war. This was a most surprising fact to me. Take geology. I had heard that geologists were attached to the Staff; but I had pictured them as mining engineers rather than as professors of the pure science. Imagine, then, my surprise when I found in one of the rooms at Headquarters a world-famous geologist studying and marking areas on a geological map of Flanders. All this country through which the battle-line passes has been studied with care by geologists for many decades, and Belgium and France have both published sets of maps showing all the geological details. On the professor's table was a map of the district directly east of Ypres; he was coloring certain areas red and others various shades of blue. He was also marking certain points and drawing a few straight lines.

Naturally I asked what it all meant. One color meant, 'Here it is safe to make dug-outs'; another, 'Here you will strike rock'; another, 'Look out for quicksands'; and so forth. The points meant, 'Dig for water.' I asked him why he did not use a diviningrod expert (only I said a 'dowser,' as I was speaking real English). He laughed and said that unofficially he might do so. The straight lines meant, 'Here you may make tunnels or burrow mines.'

I saw on the walls of the room vertical sections of the country, and inquiry brought the answer that they were for the study of underground watersystems; for the rise and fall of such might interfere with tunnels and mines, and so knowledge of them is necessary. Never have I spent a more interesting hour. It was said that one reason for the great success of the British operations at the Messines Ridge, when fifty or more mines were exploded, was the skill of the geologist who planned their location; for in some cases they were so surrounded by quicksands that the

I

Germans could not countermine. cannot vouch for the truthfulness of this, but, personally, knowing the men concerned, I believe it.

In this war the 'weather man,' the meteorologist, has come into his own. No one laughs at him now. His information is desired by the artillery officer who has to know the temperature of the air and its moisture-content, the strength of the wind at different levels, and the like, in order that he may aim his guns. When the temperature is hovering about the freezing point, the Staff wish to know if the improvised roads will be frozen sufficiently to permit the movement of guns or motortrucks. The captains of the air-squadrons must know the condition of the atmosphere up to heights of 20,000 feet. The importance of the information may be judged from the fact that we were asked repeatedly if there was not some way by which the American weather reports could be kept from reaching Germany. Our reply had to be that, with Mexico where it was, nothing could be done.

At the beginning of the war the value of meteorological predictions was not recognized by the Allies. Two incidents produced a sudden change. One morning the batteries were ordered to resume firing at the same range as on the previous afternoon; no change in elevation was made, and the shells began landing in their own front trenches, whereas the day before they had reached the enemy's lines. Such is the effect of marked changes in the air. In the early days the British weather reports leaked into Germany; and one week every condition reported indicated that for a few days ahead the weather would be such as the Germans desired for the dispatch of Zeppelins over England. The forecasters in London, however, did not, in their printed statements, tell all that they knew, and

informed the Admiralty that a change was probable which would make the conditions favorable for attack on the Zeppelins. The latter came, and found the British ready for them. From that time on the meteorologist came into favor. Now there are observing stations at short intervals all the way from the Channel to the Alps; and information is sent out, in the form of bulletins, several times a day.

Ever since gunpowder was introduced into warfare, chemistry has been recognized as the one science which was essential in preparations for war; but a new chapter was opened when the Germans introduced poisonous gases as an instrument of death, in place of bullets. This was at the second battle of Ypres, in which the Canadian soldiers suffered so cruelly. The plan then followed was to transport to the front-line trenches steel cylinders containing the liquefied gases, level down the edge of the parapet toward the British forces, letting the nozzles project over the top, and then wait for a favorable wind.

Of course, as soon as the idea of the Germans in planning this hideous mode of warfare was recognized, it became comparatively easy to block it; the preparations could always be seen; then a bombardment could be set up which destroyed the tanks where they were, much to the distress of the Germans themselves. Consequently, the manner of using poisonous gases had to be altered; and the plan adopted was to take the shells in use with the big guns and fill them with the liquefied gases instead of with shrapnel. Special guns were devised for use at short range; and these so-called gas-shells now form a most important feature of artillery.

The only protection against these gases is a mask which may be put on quickly, and which is so constructed mechanically that the man can breathe

in and out without strangling. The part of the chemist was to determine what substance should be put in the passages through which the air is inhaled, so as to absorb the poisonous gases. The way in which the French and English chemists solved this problem for it is solved - excites the admiration of the world; and the real scientific work done in connection with it is a great contribution to pure science.

When the moral question involved in this use of gas as a weapon in war was settled and the Allies determined also to adopt it, chemists were again appealed to. The result has been a study of hundreds upon hundreds of gases, their toxicity, their density, their liquefaction, and the ease of manufacture; and here again the purely scientific side of the subject will be of permanent value. The work is going on unceasingly. Chemists are attached to all the armies, and chemical laboratories are in operation; so that, if the Germans send over any new shells, — and a certain proportion always fail to explode, they may be investigated instantly. If the British line receives this favor from the Germans, the gas is studied, and the French chemists are told; and vice versa. There is complete coöperation. All the time, too, great laboratories in Paris and all over England are at work; all the chemists of both countries are government servants to-day. The men employed in actual scientific work, including testing, are numbered by tens of thousands.

Among the other ways in which chemists are helping to win the war is one which will probably strike an American as semi-amusing, although it is far from it. This is by the investigation of invisible inks. The subject sounds reminiscent of detective stories. As a matter of cold fact, England and France are thoroughly penetrated by the German spy system; and the Secret

Service officials of both countries are kept busy to the utmost of their ability in order to cope with the situation. It is much easier to devise an invisible ink than it is to discover the method by which the writing may be revealed. For, imagine a piece of apparently blank paper being found under suspicious circumstances: what should one do with it? Expose it to some gas or liquid which might bring out the written words? How can one be sure that the gas or liquid thus used may not obliterate the traces sought? This is the exact difficulty. Many inks are in use, of such a character that the obvious tests would result in a destruction of the evidence. The moral is, do not use the obvious tests. One can easily see what a field there is here for chemical investigations; and it is satisfactory to know that they have been made, and are continuing.

Other ways in which chemistry is being applied in warfare are numerous, indeed, but are almost obvious to one who asks himself how it could be used. The all-important fact is that the professional soldier has come to recognize the value of the chemist, and the latter has welcomed the opportunity for service.

Whether or not camouflage is a part of science, I cannot decide. What is certain is that the French government included it as a part of our programme of investigation of the scientific work of France. The word itself, I was told, was adopted from the stage, meaning the art of making something look different from what it really is hiding reality in the guise of innocence. This art is surely a science now, in its perfection. I was walking struggling struggling rather-up the hill on whose summit is the tiny abri known as the Fort of Douaumont, when I heard a battery of French seventy-five's' operating very near; the shells were flying within a

few feet of me. I looked around to see where the guns were, and I could not discover anything. The hill-side, as far as I could see, was simply a desolate waste of pock-marked earth, one shellhole after another. Finally I saw wisps of faint smoke, that was all. My companion smiled, and asked if I could n't see the guns. I said I could not, and he replied that he was glad, because then no enemy could either. As I was then shown, the battery was about one hundred feet away. Such is camouflage.

We saw the whole process at another time. Great nets are suspended in a shed, and bunches of dried grass, stained to suit definite conditions, are tied on; then the net is spread over the ground and elevated slightly where necessary, forming inconspicuous humps over the batteries. If the neighboring earth is reddish, so are the bunches of grass tied to the nets. When two front-line trenches face each other for some time, the observers on each side get to know each minute feature of the territory between. Then some day a photographer and an artist come to the front trench, and note with scrupulous care some object, a branchless tree, a dead horse, even a dead soldier; within a few hours an exact copy is made, having a steel framework sufficient to conceal a man; in the night the real tree or horse or man is removed, and the steel image is substituted, with its observer or listener inside. Stories are told of the two enemies trying to replace the same object at the same time, with fatal consequences to one. Other illustrations of camouflage were shown us, but I hesitate to describe them, because I am convinced that the Germans do not as yet know them all. When it comes to a combination of imagination, artistic ability, and scientific ingenuity the French people cannot be equaled.

We felt sure when we reached France

that there was at least one branch of science in which there would be but few surprises for us, if any. That was map-making. But pride met its usual fate. We saw things of which we had never dreamed, largely, I must say, because we had never visualized this war. Parenthetically I may add that no one can who has not been in the midst of it. The French had enormous difficulties in, the first months of the war. This must sound surprising to any one familiar with the wonderful maps of France which we all used when motoring or walking there in the years before the war. But war-maps must be drawn on a huge scale, showing minute details; so that existing maps must be magnified greatly; further, the accuracy required is the utmost limit attainable in the science of topography.

The Germans in their rapid sweep over northeastern and eastern France destroyed the marks of reference used on the existing maps! Consequently new surveys were necessary along the line of contact of the armies; old survey records of fields and villages on record in the district offices, corresponding to our county court-houses, were hurriedly obtained, and in a moment the new maps were ready; only the fine details had to be added gradually. But this was only the beginning; for the fighting up to now has been trench-warfare; and the progress of a battle-line forward or back is measured by feet. So that a map must show, not simply roads, churches, and bridges, but the enemy batteries, the service railroads, the trenches, shelters, fooddepots, and all the rest.

Further, different types of maps are required for different services: the Staff must have one kind, the artillery officer another, the trench-commander another, and so on, almost without limit. The complication and difficulty are increased by the fact that the details sup

posed to be revealed by a map are changing every day: new rails are laid, new trenches are dug, the positions of new batteries are discovered. As a consequence, new maps for large stretches of the front are necessary every day of the year! The facts discovered today must be on the maps in the hands of the officers to-morrow; and it is done. It is easier to imagine the organization than to describe it; but the demands upon the engineering forces of the armies call for and receive the utmost skill and scientific training.

In this rôle of aiding in making maps, air-planes are essential. Information is desired as to the enemy's country over a certain sector; up goes flight after flight of air-planes, a thousand photographs are taken, the plates are developed within a few minutes, trained observers with microscopic care compare these with the existing maps, new features and alterations are noted, and corresponding changes are made on the maps. Then reports are received from the observation-posts and the gun-locating stations, and their information is recorded; within a few hours everything is ready for the lithographing; and in twelve hours the officers at the front have their maps. The great variety of maps furnished and the rapidity of their preparation are entirely novel features of this war.

Another science which has come to the front of the stage is metallurgy. Of course, this was expected, and both France and England were prepared, in the sense that they had the men and the methods.

the methods. But many novel problems have arisen and have been solved. Chief of these were the substitution of some metal for ordinary steel, and the preparation of alloys having a light weight. Fortunately, it has been the practice in all countries to employ, in connection with the great steel works, groups of scientific men, chemists and

physicists; and the realization of their importance is no new feature of the

war.

III

Physics is a science which covers many subjects. Of these, acoustics is one to which in recent years less and less attention has been paid, owing to the apparent growth in importance of other subjects, notably electricity and temperature measurement. In fact, I know several institutions one is the greatest school in England - where acoustics has been omitted altogether from the one-year course in Physics. And now, to a physicist, the most striking feature of this war, so far as science is concerned, is the wide use of the phenomena concerned with sound. Yet, when one stops to think, there is nothing in this to cause surprise. One of the needs of a combatant is to detect the presence and position of one's enemy: air-planes are very noisy; when a gun expels a shell there is a sound; and submarine engines cannot be made noiseless. Again, sound-waves may be emitted from any such source as a horn or a whistle, and may be used for signals on a dot-and-dash system, or use may be made of their echoes.

Here was a wide field at once for physicists; and both in France and in England we saw the results of their work. Perhaps the most interesting of these was the method of locating the position of a gun of large calibre. When a shot is fired from a German gun toward the Allies' line, the observer in the latter hears three sounds. The first of these is the sound due to the passage of the shell through the air - this is this is because the velocity of the shell is greater than that of sound-waves; the second sound to be heard is the boom of the gun itself; and the third is that due to the explosion of the shell. So, if there are two or more 'receiving staVOL. 121 - NO. 1

tions,' at each of which some such apparatus as a simple microphone is installed, and if each of these is connected by wires to a central station where there is a recording device, each microphone will register the arrival of the three sound-waves; but, since the receiving stations are at different distances from the gun, any one type of waves, for instance, the 'boom,' will reach them at different instants of time. In order to know the time-intervals, all that is necessary is to make an extremely accurate clock record its indications on the same strip of paper that receives the microphone signals. Then, knowing the velocity of sound-waves, as we do, and also the exact situation of the receiving stations and their relative distances, it is a simple matter to work out graphically the position of the gun.

The only uncertain element in the process is the velocity of the soundwaves, because it varies with the temperature of the air-fortunately in a known manner; and it is affected by the wind, if this is strong. But corrections can be made, and the accuracy obtained is truly surprising. One way of verifying the result is to send up an air-plane and photograph the region. When this is done, it is found that the two methods agree so closely that, if on the largest scale maps a gun's position as determined by one is marked by a pin, the position as found by the other cannot be marked by a second pin there is not space. This means roughly that the location of a gun at a distance of six miles can be determined definitely within some fifty feet, which is sufficiently close. The English officer who had charge of the sound observations at the Messines fight told me. that in one day sixty-three large German guns were located, and all sixtythree were destroyed. Naturally, the receiving stations have to be close to the front line, and the central station