International Water Technology Exhibition in Liege 1939

May 20, 1939 - September 2, 1939

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Universities at the Exhibition Expo Liege 1939

© Sergysels

Architect(s) : Paul Fitschy, Klutz et Tibeaux

This beautiful palace was, without doubt, an excellent study in functional architecture. The volumes faithfully reflected the plan inspired solely by the need to showcase the exhibits perfectly and, above all, the obligation to lead the visitor through all the stands without fatigue. The route was laid out with great ingenuity. The visitor was taken directly to the highest floor by a gently sloping ramp and, by an easy staircase, he descended to the lower levels after being led through all the stands.

With its very modern architecture, well-balanced solids and voids, the Palais des Universités was one of the best applications of the standard steel frame. This framework became one of the main elements in the composition of the facades. The elegant glass roof on the right gave a glimpse of the interior walkways. However, we had to regret that the access ramp was less an architectural achievement than a scaffold. On the other hand, we would have preferred a lighter canopy.

The Sciences

The first three classes of the General Programme were entitled respectively: "Sciences in their relationship with Water", "Water in the Sciences and Applied Arts", "Water in Nature".

By giving pride of place to scientific activities, the intention was not only to conform to a tradition, but also, and above all, to mark the character of the Exhibition placed entirely under the sign of science and technology.

All the national participation in these three classes, except for the industrial part of the last one, was gathered in a vast palace called the Palace of Universities. The aim was to present a synthesis of the studies and annotations of scientists on WATER and its properties, and to show how Belgian education cultivates and transmits this knowledge. As will be seen later, the subject matter was so extensive that most sections of our scientific institutions were represented.

The whole produced the best impression and gave a high idea of the value of our higher education. What was most striking was the harmony in the presentation. The organisers were able to avoid the disadvantages of the individual stand. They drew up a general plan by science groups, to which all institutions were invited to contribute. This
This plan was scrupulously carried out: each science or part of a science thus had a unique, homogeneous and complete stand.

The Universities of Brussels, Ghent, Liège and Leuven, the Polytechnic Faculty of Mons and the State Agronomic Institute in Gembloux, the Queen Elisabeth Medical Foundation, the National Fund for Scientific Research, the Royal Meteorological Institute and the Geological Service of Belgium took part in this event. Finally, a number of industrialists lent their support by exhibiting equipment to complete certain stands.

As we cannot name all the exhibitors and their numerous collaborators, we would like to express our collective praise to them. Their perfect spirit of collaboration produced the unique thing that was the Palais des Universités at the 1939 Liege Exhibition. It was a striking demonstration of the vitality of our universities, colleges and scientific research institutions.

We would like to remind you that it was Mr. J. Duesberg, former minister, Commissioner for classes 1 and 2, who presided over the general organisation in his capacity as rector of the University of Liège.

The following description is limited, in general, to the enumeration of the demonstrations presented: their number and their interest were such that an entire volume of the size of this one could have been devoted to them. It takes into account the grouping of the sciences by the General Classification and follows more or less the order in which the stands followed one another as the visitor walked through the Palais in the one direction imposed on him.

Let us start with the PHYSICO-CHIMIC section where the first problem studied was the composition of water. The first problem studied was the composition of water. Water was decomposed into its two constituents î hydrogen and oxygen, by electrolysis and by thermal process. Then it was reconstituted by combining the two elements. As this synthesis produces a lot of heat, it was easy to demonstrate the industrial application of this phenomenon, in the oxhydric torch, for example.

The visitor then discovered everything that is currently known about the structure, dimensions and properties of the water molecule (internal vibratory movements, electrical polarity), as well as the catalytic action of water and the importance of its role in chemical reactions.

On display were a Weboba Pigrez distillation apparatus with automatic feed, a De Stadler distillation apparatus and a universal tensiometer for determining the value of the static or dynamic surface tension, as well as the interfacial tension exerted at the contact surface of two non-harmful liquids.

Further on, at the ANALYTICAL CHEMISTRY stand, devices (two Poggendorff potentiometers and two Kohlrausch bridges) illustrated the influence of physical chemistry on all branches of chemistry, and in particular on analysis, over the past fifty years. In addition to demonstration models, the exhibition featured sophisticated, high-precision equipment. Tables showed the connections of the potentiometer and the Kohlrausch bridge and gave the results of a potentiometric determination of a silver salt (Ag NO3) with an alkaline chloride (NaCl) and a determination of hydrochloric acid with caustic soda titrated by the conductometric method.

No less interesting was the section on COLLOIDAL CHEMISTRY which presented some properties of colloids. It is known that the Tyndall effect indicates how, in a colloidal solution, the particles scatter the light. This phenomenon can be observed with the ultra-microscope. It also allows the observation of Brownian motion, similar to that caused by the thermal agitation of molecules.
An apparatus, specially designed for this purpose, revealed the heterogeneity of colloidal solutions by ultra-filtration methods.

Models showed that the simplest colloidal micelle (colloidal particle) is in fact a complex structure containing a large number of atoms. Small glass tubes symbolised the cohesive bonds between molecules and, in particular, the hydrophilic bonds. The models represented the three main types of colloids. A starch micelle, identified with a very large chemical molecule: true colloid; a soap micelle, an aggregate of a large number of smaller, more or less identical molecules: aggregation colloid; and finally, a micelle formed by a particle of graphite in suspension stabilised or peptized by absorbed soap molecules: composite colloid.

The APPLIED CHEMISTRY exhibition focused on metal corrosion, river pollution and wastewater treatment.

Simple experiments demonstrated the action of different corrosion factors. Attention was drawn to the methods used in laboratories to compare the relative resistance of metals (Thysen-Bourdouxhe method, Nylius method, salt spray test, alternate immersion test) and to all modern protection processes.

The problems of river pollution and wastewater treatment were then reviewed. On a panel, all the vicissitudes of a river were schematised. In addition, the field and laboratory equipment used for water and sludge sampling, a net for plankton collection, equipment for physical, physico-chemical, chemical and biological tests were assembled. Finally, there were plans and diagrams of the wastewater treatment methods.

More important was the participation of PHYSICS, which grouped together demonstration devices of great interest and whose general theme was the physical properties of water.

The first point dealt with by the experiments was hydrostatics. An illustration of Pascal's principle or equipartition of pressures was shown. The notion of hydrostatic pressure, the principle of communicating vessels and Archimedes' principle were highlighted by simple experiments of great didactic interest. Another experiment showed the equilibrium of water subjected to a rotational movement, highlighting the principle of the centrifugal pump.

Hydrodynamics was then considered and the law of pressure drops or head losses in pipes was established. The principle of the water tube was also demonstrated.

After that came experiments relating to surface and capillary phenomena. They compared the case of water with that of mercury, which, from the point of view of capillarity, behaves in the opposite way to water. A tension balance measured the value of the surface tension. The diamagnetism of water was also demonstrated.

A series of experiments showed the phenomenon of the propagation of waves on the surface of water in an aspect that allowed, by analogy, an easy understanding of the problem of the propagation of light waves.

Finally, the phenomena of reflection and refraction were reproduced, as well as the classical experiments of Fresnel and Newton on interference.

In addition to the purely spectacular phenomena, the OPTICS section presented explanatory experiments as well as demonstrations of some properties of water as an optical medium.

These included the creation of a small water jet and a luminous fountain: experiments showing the absorption of infrared radiation by water, a reproduction of the photographic halo and the production of a miniature rainbow. Finally, the visitor was given a demonstration of mirage, which, as we know, results from the refraction and reflection of light rays in layers of air of different densities.

Then came the important stand of SPECTROSCOPING, mainly considered from the point of view of the applications of the spectrographic method to scientific and industrial analyses.

A schematic table showed the simplified spectrum of a mixture of lithium, sodium, strontium and copper. An example of direct quantitative analysis was given by a photoelectric bi-spectroscope which allowed the composition of a binary mixture to be read off immediately.

In a showcase was a large double-armed spectrograph, a state-of-the-art instrument for photographing any spectral region from 1,910 to 12,000 Angstrom wavelengths, either with quartz optics for the ultra-violet or with glass optics for the visible and infrared.

An installation for spectrographic analysis using high-frequency electric current was also shown. Next, the successive phases of a spectrographic water analysis were presented. This includes the recovery of the water residue by slow evaporation, the collection of the quantity of residue necessary for a complete analysis and the carrying out of this analysis by means of an appropriate spectrographic installation, and finally the obtaining of images giving the results of the analysis.

The NUCLEAR PHYSICS AND CHEMISTRY exhibition included a fully equipped laboratory for the production of artificial radioelements from heavy water. It included a very high voltage (1,000,000 volts) direct current generator of the dust type designed and built at the Institute of Physics of the University of Liege (by Messrs. Max Morand and André Raskin) and a neutron producing tube built by the Philips Factories. This tube receives heavy hydrogen extracted by electrolysis of heavy water, - the electric discharge, fed by the high-voltage generator, produces hydrogen ions. These are launched by the action of the high voltage, with considerable speed, onto a lithium target,- under the action of this bombardment, the target emits neutrons. These are used to give ordinary, stable bodies radioactive properties identical to those of naturally occurring radioactive elements. The demonstration therefore consisted of bombarding bodies with neutrons and observing the radioactivity thus produced.

Since atoms of the same chemical species, whether radioactive or not, move in the same way, the radioactivity of some makes it possible to follow and measure the movement of others. This remarkable property provides physical, chemical, biological or technical applications, the number of which is limited only by the still very small quantity of artificial radioelements that can be produced.

Artificial radioelements still make it possible to study the central region of the atom, i.e. the nucleus, on which all the physical and chemical properties characteristic of each chemical element depend directly or indirectly.

Neutrons can be used, either directly or indirectly, for the treatment of cancerous tumours. This shows the importance of the study of nuclear phenomena.

Various devices (Wilson chamber, radiation counters) made it possible to measure the radioactive phenomena obtained.

A model of a cyclotron electromagnet was also presented. This model was used to make a methodical study of the best conditions for the realisation of this apparatus which would naturally find its place in a nuclear physics and chemistry laboratory, next to the high voltage installation and the ion tube.

The ANIMAL AND VEGETABLE BIOLOGY section began with an interesting little exhibition showing all the details of a section made in a plant using fluorescence microscopy.

The rapid movements, either intra-cellular or of the whole organism, in aquatic plants were particularly highlighted.

A series of microphotographs of sections obtained with the help of an ultraphotographic apparatus (microscope and camera combined) made it possible to render perceptible a part of the anatomy of aquatic vascular plants. The microphotographs were presented in slide form under the aquaria containing the plants.

Few people realise that microbes of a few thousandths of a millimetre can, under certain circumstances, form masses of several tonnes in a few days. This is, however, the case with leuconostoc. This is the name given to gummy masses that can be the size of a man and formed by the symbiotic association of three organisms. They develop in industrial sugar liquids, destroying a considerable quantity of sugar and causing numerous problems (clogging of pipes, stoppage of machines, etc.).

In order to make their extraordinary activity striking, these microbial masses were exposed and cultivated in two strongly illuminated glass cylinders. One could thus observe the sort of explosions that were continually produced by the release of the carbonic gas formed, violently throwing the gum debris. The phenomenon ceases, either because the medium is exhausted of sugar, or because of an increase in acidity.

The rapid growth of plants has been the subject of very interesting research at the Botanical Garden of the University of Ghent. Some species, when placed in suitable conditions, grow at an accelerated rate. For example, the petioles of 'Nymphaea' can grow at a rate of 10 to 20 centimetres per day, while those of 'Victoria' and 'Limnanthemum' grow at an even faster rate of 30 centimetres per day or more. Petioles 10 to 12 centimetres long were observed to have tripled or quadrupled in length within 24 hours.

Photographs showed plants of 'Limnanthemum Nymphacoides' and 'Sagittaria Sagittifolia', both of the same age, growing in shallow water (12-15 cm) and thick water (80 cm) respectively.

The growth can be recorded by the plant itself using an auxanometer. Two auxanograms were visible at the stand. Speeds of 10 to 15 millimetres per hour were observed and maintained for several hours.

The growth of the peduncle is sometimes even faster than that of the petioles described above; slow at the beginning, it progresses more and more rapidly. The following observations have been made: 46 centimetres in 24 hours, 15 centimetres in 7 hours, 25 centimetres in 12 hours, etc. The phenomenon was clearly observable in the case of the two types of plants. The phenomenon was clearly observable in the aquariums.

Aquatic plants bring about changes in the chemical composition of natural waters through the quantity and quality of dissolved salts. Under the influence of sunlight, they assimilate carbonic acid and release oxygen. A detailed study of this phenomenon on the "Elodea Canadensis" was represented in a table showing an increase in the pH of the water and a decrease in its alkalinity.

In a beautiful series of aquariums, there were various sea anemones, crabs, lobsters, hermit crabs, spirographs and ascidians, dentexes, skates and rays, sharks, triangles, seahorses and coral fish. The marine animals are preserved and can be cultivated for years in artificial seawater, without any renewal. This makes it possible to undertake biological studies of marine species in continental laboratories far from the sea. To avoid putrefaction, which is harmful to the animals, the water is constantly filtered through a special charcoal, the activated charcoal.

The study of the respiratory function of blood in aquatic animals was the next focus of attention. It is known that the substances present in the circulating blood and capable of being loaded or unloaded with oxygen molecules, depending on the case, are chemically very different in nature, apart from their common property of being oxygenable. Photographs showed their appearance as crystals and a preparation of hemerythmy was visible under the microscope. These substances have a characteristic absorption spectrum. The spectrum of haemoglobin was visible under the microscope.

The comparison of the absorption curves of different aquatic animals is very instructive. This was illustrated by comparing the blood oxygen uptake curves of carp and trout. The uptake curve of trout rises much less rapidly than that of carp. In other words, the complete loading of the carp blood is accomplished at a much lower oxygen pressure than the trout blood, which explains why the trout suffocates in poorly aerated water, in which the carp lives perfectly.

Finally, the extraction of active principles from plants and their chemical study were illustrated by a series of operations carried out on "Hippuris Vulgaris L.", the only Belgian representative of the Hippuridaceae family.

A small stand devoted to HYGIENE allowed a series of devices for the sampling and study of water to be reviewed. One of these was used to demonstrate the possible contamination of underground pipes by dirt.

In addition, there were two Dunbar devices, one for taking river sediments, the other for taking water samples at various depths by means of a graduated chain, a Heyroth device for drawing water at various depths and a Marboutin device for searching for fluorescein in order to establish the underground path of the water. On the wall was a map of Belgium at 1/40,000 indicating springs and resurgences.

An adjacent section was devoted to the preponderant part of WATER IN FOOD.

It is known that the human body, both in adults and in newborns, contains a high proportion of water, about 2/3 of the total weight. In general, the foods that allow growth and sustain life also contain a large amount of water. Vegetables and fruit contain so much water that they sometimes allow people to abstain from drinking. The proportion of water and dry matter in various foodstuffs was shown in tables.

Based on the composition of the foodstuffs, the daily intake for a person at rest and for a person at work can be calculated, as well as the quantities of water absorbed. Three large tables provided an overview.

The participation of THERAPEUTICS included a model of a hydrotherapy institute and diagrams showing the action of different drugs on diuresis, the possibilities of
of the nerve centres, renal filtration in the state of health and in pathology. In addition, various techniques relating to hydrotherapy (this term being taken in its broadest sense) including a carbogas bath and peat bath chamber, a foam bath chamber, a neutralising fog device for toxic gases, a single water and carbogas fog chamber, a thread-like shower installation, a 16-atmosphere rubber shower, a "spray gun" shower, a diving apparatus, an oxygen therapy installation designed so that oxygen can be administered both during and outside the gas bath, an individual and collective oxygen and gas therapy installation.

We owe the installation of natural carbogas baths and peat baths to the Compagnie fermière des Eaux et des Bains de Spa. We know the importance of the natural carbogas bath in the treatment of cardiovascular diseases, as well as the results obtained in rheumatism and gout by the Fagnes mud bath.

Research carried out in the laboratories of the Spa resort has shown that carbogas baths have a particularly favourable effect on peripheral circulation and that they help to improve cardiac contraction.

Studies carried out in Spa on mud baths, using precise physiological methods, have shown their strong action on circulation, respiration and diuresis.
In addition to bath therapy, various inhalation methods were used: inhalation of carbogas water by means of a jet, inhalation of steam at variable temperature as a vehicle for pure oxygen.

Among the showers was a "spray" shower which massages the entire skin surface with fine droplets of carbogasous water dispersed under pressure and temperature. This massage is indicated in the treatment of certain circulatory stases and in particular acrocyanosis.

The apparatus for diving to small depths, made by the Englebert Company, is also worth mentioning. It can also be used in toxic atmospheres (forts, shelters, sewers, mines) and in industries requiring the isolation of workers (crushing, cement works, etc.).

In the water therapy section, there was also a stand devoted to gas therapy with a rescue installation equipped with the apparatus. It seemed interesting to consider the therapy of asphyxia, especially by drowning: most of the first aid stations on the coast and along our waterways still lacked "revival" equipment. Not only were individual oxygen and carbotherapy devices shown, but also a collective gas therapy installation. This collective equipment is intended for hospitals, first-aid stations, ambulance cars, field outposts, etc. It is indicated in particular for the treatment of patients who have been injured in a fire. They are particularly suitable for the treatment of gas poisoning.

In order to objectify the renal function and the effect of disturbances that could influence it, various nephron casts were made. The glomerulus with its afferent and efferent arteries, the proximal convoluted tube, the intermediate segment, the distal convoluted tube and the collecting tubes of Bellini were shown.

Finally, the therapy stand was completed by a model of a physiotherapy institute floor, reduced to a tenth of its original size and ideally suited to water therapy. All types of simple and mineral artificial baths as well as the entire range of medicinal baths can be performed here. A complete shower room shows fixed and mobile shower types in various locations. Another room is set up for the application of mud and paraffin with the equipment for the preparation and cleaning of patients. The massage under water at high temperature and high pressure is carried out with the help of the most modern equipment. The Vichy massage shower is also provided. Around a cold water pool are the Turkish and Roman baths (hot air and steam). A warm water pool is used for mobilisation and motor rehabilitation of paralytics under water. Mechano-therapeutic devices can be immersed for the treatment of
post-traumatic sequelae and joint stiffness of the lower limbs. Four-cell and general hydroelectric baths are feasible. Next to the foot baths, submerged walkways with sand and gravel bottoms are available for the treatment of flat feet. The facility is completed by a gynaecological hammock shower, single and multi-jet sitz baths and a special device for administering a large enema, underwater.

The GENERAL ELECTROTECHNICS section presented a demonstration of the effects of thunderstorm discharges on power lines. It is known that atmospheric discharges during thunderstorms (lightning strikes) subject electrical networks and connected equipment to extremely severe tests. The construction of equipment that can withstand these stresses therefore requires experimental study. This is the reason for the existence of shock wave generators capable of reproducing the electrical stresses resulting from these discharges.

The principle of these stations is to charge capacitors in parallel and discharge them in series by applying the voltage thus produced to the object to be tested. The 700,000 volt station shown was set up according to the following diagram. Fourteen capacitors of 0.2 microfarad each are grouped two by two and charged in series-parallel by a 115/75,000 volt transformer through liquid resistors and a kenotron (rectifier tube); when the capacitors are charged, the voltage is 75,000 X y 2 = 106,000 volts. At this moment, the spark gap operates, causing the first two stages to be put into series and, in turn, the 14 capacitors to be put into series, whose voltages are added. This gives a discharge voltage of about 700,000 volts, taking into account the losses in the spark gaps.

The following experiments could be carried out with this installation:
a) The discharge path, i.e. the path followed by the electric discharge following the lightning strike and which is determined by the general laws of electricity: it is in principle the path of least resistance;
b) The bypassing of an insulator: a spark flying between a cloud and a
(b) Bypassing an insulator: a spark strikes between a cloud and a line wire, the latter is raised to a very high potential and a spark that bypasses an insulator strikes the line towards the pylon.
c) The influence of the earthing of the pylons: when the discharge occurs on a pylon resting on wet earth, constituting a good earthing, the current flows easily without producing any disturbance. But when it occurs on a pylon placed in a pit filled with dry gravel, due to the electrical resistance of the gravel, the pylon is raised to a high potential and a bypass occurs from the pylon to the line.
d) Ground wire protection: If an electrically conductive ground wire is placed above a line, the line will not be affected by the discharge. The earth wire also has a very marked
The earth wire also has a very marked attenuating effect on the overvoltages produced by electrostatic induction;
e) Protection by lightning arresters: these are used to discharge to earth the currents due either to indirect discharges or, if their capacity is sufficient, to direct lightning strikes. Modern lightning arresters consist of two elements arranged in series: a spark gap and resistors which limit the line voltage to a value compatible with its insulation, i.e. approximately 2.5 times the operating voltage. Since lightning arresters, like pylons struck by lightning, have to discharge large quantities of electricity in a very short time, they must be connected to a good earth connection, otherwise they will be useless.

In its two parts, drainage and irrigation, the participation of AGRICULTURAL HYDRAULICS highlighted the relationship of water with the soil and the cultivated plants, according to whether there is an excess or a shortage of water.

A model showed the construction of a modern drainage system. In the centre, the sequence of works to be carried out: on the one hand, the staking and staking of the ditches, the digging of the drainage ditches and collectors and the adjustment of their slope, the placing of the drains and their connection to the collectors, the backfilling of the ditches, - on the other hand, the regularisation and rectification of the outfall, the construction of the mouth of the main drain, as well as the manhole allowing the correct functioning of the drains to be checked. The left and right parts of the model showed respectively the aspect of a non-drained land and a land having benefited from this operation.

Drainage of this kind is costly and requires skilled labour. Other simpler and, above all, less expensive methods were sought. This is the origin of mechanical drainage, which uses machines to dig an underground gallery or "molehill". Photographic views showed the various types of machines designed for this purpose.

Four models illustrated the different processes of irrigation by gravity, and a group of photographs represented the equipment and the execution of irrigation by modern processes.

Finally, various tables provided information on the role of water in vegetation and farming.

The imposing CIVIL ENGINEERING set offered a complete illustration of the testing and control procedures of materials.

Firstly, a laboratory apparatus subjected the paints in an accelerated way to the effects of the main agents to which they are subjected in their normal conditions of use: humidity, frost, desiccation, solar irradiation, possibly the action of more or less aggressive atmospheres and solutions.

The effectiveness of paints in protecting steel against rust was the subject of particular experimentation. The study of the corrosion of cement mortars and concretes was illustrated by mortar specimens immersed in aggressive solutions and by Anstett tests on various cements.

A device for the study of capillary rise in sands and another recording the density increase resulting from the suspension of earth in water were also presented. A model of an earth dam and a model of a caisson gave the public an idea of the conditions that such constructions must meet. An odometer was used to determine the relationship between the compression of the soil and the resulting settlements. The permeability coefficient of Darcy's law was studied by means of a special apparatus.

The stand reserved in this section for HYDRAULICS provided a complete set-up for a laboratory intended to serve both as an illustration of the oral instruction given to students and to pursue advanced research. The laws of similitude and the value of the elementary theory based on the Euler equation were verified. The set-up was also used to demonstrate the phenomenon of pre-rotation, which can be heard by means of a few air bubbles that are allowed to enter the inlet of a horizontal glass suction pipe and which show the rotational movement of the water before it reaches the impeller blade. Diagrams were produced showing the results of the tests in the form of characteristic curves.

The considerable industrial importance of the exact measurement of flow rates in pipes is undeniable, - it always results in appreciable savings and allows easy control of the manufacturing process. It is essential in the testing of machines in which any fluid is used as a source of motive power or must itself be set in motion. Various measuring methods were presented.

Further on, there were some applications of Bernouilli's theorem, the importance of which results from its extreme generality. It applies not only to the study of the flow of all liquids, but also, with a slight modification, to all compressible fluids, and it can even be used to study transient phenomena.

It is important to know exactly the laws of pressure drop, as they determine the flow rate that a pump is capable of delivering through a pipe. Comparative measurements showed how pressure losses are a function of the width, material and structure of the pipes and that they vary according to the regime of the liquid passing through.

There was also a device designed to demonstrate the mechanism of formation and the value of the action and reaction of a liquid jet, a demonstration of the well-known phenomenon of backwater, which is the transition from an upstream hydraulic axis (rapid flow at low height) to a downstream axis (low velocity and high height), and various models of bridge piers made of paraffin-coated wood, which allowed the intensity of the erosive action of the water around them to be measured. There was also a hydraulic reel giving the speed of the water and, on the same tank, an apparatus with special devices for determining the speed of the water at a particular point in the current with great accuracy. Finally, a weir reproduced the various overflowing slicks: free, depressed, adhering, plunging, adhering with air bead, undulating with and without air, etc. An experimental channel showed the phenomenon of a surface rise moving with the height of the downstream level.

This experiment also illustrated the phenomenon of the tidal bore in the estuary of some tidal rivers. A device for measuring the permeability of sands determined experimentally their permeability coefficient, which is essential in geophysics.

In addition, the hydraulics stand included several demonstration or study devices, including
- Flow visualisation devices: the aim is to make the liquid threads visible in order to highlight their characteristics. This is achieved either by colorimetric processes (permanganate channel) or by means of suspended matter;
- Devices for determining the flow of watercourses by chemical means, a method which is particularly appropriate for small watercourses, and especially for those in the mountains (torrents);
- An apparatus for the determination of velocities by the chrono-photographic method.
The section on hydraulics also included numerous explanatory
explanatory diagrams, photographs of the Belgian laboratories and the work carried out there; finally, a large plaster model used to study the different possible water flow regimes of a hydroelectric power station dam in the Belgian Congo.
It should also be noted that an important participation of hydraulics was housed at the neighbouring stand of shipbuilding. On the one hand, there was a hydrodynamics exhibition with :
- Apparatus for the graphical solution of conformal transformation problems, whereby a two-dimensional irrational flow field is studied as a derivative of another simpler field: both fields being defined by certain functions of complex variables
- A demonstration channel in which the intensity of the action of the current on various obstacles of the same cross-section, the intersection of these, the formation of wakes and, in general, the various flow configurations were measured with the aid of small hydrodynamic scales.

In addition, a subsection on hydrography dealt with the measurement methods used in maritime as well as river hydrography. There was a tide gauge recording both tidal level variations and swell amplitude and frequency, recordings of diagrams from a diving tide gauge, the Favé system (recording pressure variations on the seabed), an Idrac type reel measuring both the speed and direction of underwater currents by photographic recording, a hydrometric reel for measuring the size and direction of a current in the immediate vicinity of the seabed, photographs of sounding devices, various limnimeters or limnigraphs, and finally, devices intended to measure the solid flow in the currents, either for materials carried on the seabed or for those suspended within the liquid mass. These last devices were mounted, along with various hydrometric reels, on an installation intended to be used for measurements in rivers and which comprises two parallel metal boats joined by a working floor carrying the devices.

The NAVAL CONSTRUCTIONS stand presented the most recent aspects of naval architecture technology: plans and models of hulls and boats, drawing instruments used for their layout, an integrograph used for stability calculations, and a whole range of equipment for colonial navigation.

A special exhibition concerned tests on scale models to determine the resistance of ships in the Albert Canal. These tests, and their interpretation, taking into account the laws of similarity, make it possible to find the most advantageous shapes for the hulls and to predict with remarkable certainty the performance of sea-going vessels. For inland vessels, such as those in question here, the vessel is studied in relation to the channel on which it is to navigate, since the resistance to forward motion also depends on the characteristics of the waterway channel.

The tests were carried out on wooden models, covered with paraffin, of boats of the Campinois type of 600 t., on boats similar to the Rhine boats of 1,350 t., and even on a boat that can hold the sea whose transverse dimensions are the maximum admissible in the Albert Canal. The tensile forces were measured by dynamometers and the results obtained were plotted on plates and graphs showing, for the various types studied, the tensile forces as a function of the speeds and the influence of the ratio of the canal cross-section to the cross-section of the vessel.

Finally, in a glass tank, a hydraulic circuit was created for the study, by the classical method of chromophotography, of flows around immersed bodies. Models of propellers allowed the comparison of the most modern forms, - photographs showed mainly the installations of the various foreign test basins.

In the first stand of the GEOLOGY section, which was mainly devoted to hydrology, the conditions of the deposit of water used, on the one hand, for human consumption and, on the other hand, for industrial needs were shown. Decorative panels showed the distinction between surface water and groundwater, damming for surface water use and a type of large groundwater (London Basin). One of the geysers in Yellowstone Park in the USA was an example of gushing water in relation to volcanic phenomena.

Hydrology was studied first in relation to meteorology. Diagrams showed the water cycle, the distribution of rainfall in relation to latitude and altitude. There was a planisphere showing the distribution of rainfall on the surface of the globe and commonly used devices, the most useful of which is the rain gauge.

Water from rainfall runs off the surface of the ground. Maps of river systems in permeable and impermeable soils showed the effects of runoff, and photographs illustrated the harm it does. A few simple experiments showed the influence of soil type, especially permeability and slope, on runoff. Water that penetrates the soil forms underground networks. A distinction is made between impermeable rocks, small permeable rocks and large permeable rocks. Samples were taken to show their respective characteristics. Apparatus were used to measure the permeability of certain rocks and the speed of water flow within them. The apparent paradox of the increase in permeability of rocks with grain size is explained by the relationship between void size and capillarity.

The underground reserves form various types of aquifers, the interrelationships of which were shown in diagrams. The shape of an aquifer, its variations in level, the influence of a catchment on its shape and the way in which contours or springs are formed were also shown. Various special cases were considered, including groundwater in alluvial deposits and aquifers in dune regions at the seaside. It was seen that fresh water discharges seawater to an equilibrium surface below sea level.

For confined groundwater, a model showed the variations of the piezometric level in a moving confined groundwater.

The composition of water in relation to the terrain was the subject of a special chapter. Various types of water were shown: Ardennes water, calcareous water from Liege, ferruginous water from Spa and
the deposits formed by the water. Devices were used to determine the turbidity of the water and its resistivity. It was then shown how it is possible to purify them: natural purification in the filtered rocks, bacteriological purification, improvement of their chemical qualities.

The regulation of surface water flow was shown by sketches and models of dams, - photographs, maps and models showed how groundwater is collected, especially in the case of regions with constantly frozen ground.

A large wall map showed a project to supply drinking water to the whole country through five interconnected networks. A display case contained various publications relating to hydrology.
A special place was reserved for limestone. Rock samples, maps, drawings and photographs showed how water flows in these terrains.
At the stand of the Geological Survey of Belgium, four documents were exhibited that were characteristic of the main stages involved in the progressive implementation of the new data that it is constantly gathering. These were a cross-section of the artesian well of the Palais des Thermes, in Ostend, - a cross-section of the division ridge between the Samme, a tributary of the Senne (Scheldt basin), and the Piéton, a tributary of the Sambre (Meuse basin) a map of the deep boreholes in the Brussels conurbation, with a representation of the relief of the bedrock and the extension of the Cretaceous cover on the surface, - finally, a sketch of the entire national territory and the border regions, conceived in the same spirit and defining the age of the immediate cover of the Paleozoic basement.

Following on from the geology, the PHYSICAL GEOGRAPHY contribution included maps of Belgium showing the limits of the saline and over saline zones in the deep aquifers.

The role of water in human geography was highlighted by a series of maps, plans and photographs showing successively:
- Man and water in temperate regions. A relief map of the Mosan basin showed how the distribution of industries is related to the hydrographic network; another map showed the distribution of the population according to this network and proved that running water has exerted a real attraction on the location of men. Finally, the distribution of settlement sites is also closely linked to the manifestations of karst activity, such as the disappearance of running water in the chantoirs or aiguigeois and its reappearance at the resurgences.
- Man and water in semi-arid countries where irrigation is an improvement (Algeria, Western USA, India);
- Man and water in arid countries. The water necessary for agriculture is the only condition for the location of men (Sahara) ,-
- Man and water in a humid tropical country (Indo-China). Water has a decisive influence on the location of people and their economic life.

In the same stand, maps and models gave an overview of the hydrology of Flanders. Models showed the nature and layout of the various terrains in East Flanders, whose hills are rich in springs. This region has groundwater reserves - the industrial centre of Cour-trai was specially studied from this point of view.

The METEOROLOGY section contained the basket of the stratospheric balloon "F.N.R.S.". We remember the famous ascent of August 18, 1934, which allowed us to make observations of great scientific significance, especially on cosmic rays at different altitudes, on the variation of the intensity of these rays with latitude, as well as on the composition of the air at high altitudes and the wind regime in these regions.

Most of the equipment used in meteorology was displayed in showcases: an actinometer, different types of hygrometers (condensation hygrometer, hair hygrometer), thermo-hydrographs, a meteorograph for aeroplane sounding (whose characteristic is to be fixed outside the thermal disturbance of the aeroplane's engine and attached by an elastic suspension that removes it from both wind and mechanical vibrations), a meteorograph for a sounding balloon (including a capsule barometer, a bimetal thermometer and a hair hygrometer, weighing 80 gr. ), a Jaumotte radio-sonde (weighing a full 350 gr. which contains, in addition to a barometer, a thermometer and a hygrometer, a small electric motor handling a short-wave T.S.F. transmitter of 11 m. 50 and making the data of the apparatus immediately usable) and a Campbell heliograph.

Other display cases contained barometers, barographs and a Cosyns radio probe for studying cosmic rays. This last device includes a counter sensitive to these rays, an amplifier and a radioelectric transmitter with a wavelength of 11 m. transmitting a signal when each cosmic ray passes by: a transmitter activated by a barometer transmits the altitudes. It weighs a total of 750 grams.

In addition, various anemometers (hand-held anemometer, high-precision electric anemometer, Fuess anemometer with totalizer), a rain gauge and a snow gauge of the "Royal Meteorological Institute" type, a thermometric shelter from the Belgian climate stations (where the devices are placed in a louvered cage that protects them from radiation) and a theodolite for wind sounding.

The National Fund for Scientific Research, with diagrams, recalled its activity since its foundation and, in particular, the important subsidies granted to science, industry, as well as to a large number of researchers, associates, aspirants and technical collaborators. A plaster model represented the excavations at Apamea, while photographs showed the missions and experimental stations that the institution supported.

The Association des Elèves des Ecoles spéciales de l'Université de Liège also exhibited copies of its bulletin and the courses it has published.

We hope that this brief description of the Palais des Universités will give the reader an idea of the importance of Belgian scientific participation. It will be realised that
the number and interest of the disciplines presented made it a section of the highest value.

What can be said of the presentation, except that it was perfect. The interior layout had been carefully studied to allow the visit in the best possible conditions.

Let us add, in conclusion, that the International Jury of Awards has fully confirmed the value of this participation: almost all the exhibitors were awarded the Grand Prix. It is in classes 1, 2 and 3, moreover, that the percentage of first category awards was the highest for Belgium.

© General Report - International Water Technology Exhibition - Liège 1939