Science and Industry

FIELD archaeology today is a race against time. The threatened submersion of the great Abu Simbel statues of Ramses II by the dammed-up Nile is only the most spectacular example of what is happening all over the world. Greek road machines are cutting through burial mounds old in the age of Homer. The weight of tractors tilling Italian fields crushes vaulted Etruscan tombs hidden beneath the sod. The foundations of skyscrapers in Mexico City root out the remains of Aztec towns. In our Southwest, pipelines trench through the remains of ancient Indian kivas.

Everywhere, as populations explode, the archaeologist must rush to keep ahead of the bulldozer. In one year British scientists had to carry out forty-four “rescue digs” as gravel diggers burrowed into prehistoric village sites. American scientists have hastily surveyed three hundred areas in the West about to be covered by reservoir waters. In China, archaeologists are reported hurrying to investigate three thousand ancient tombs in the path of a new industrial city. And in Egypt archaeologists of sixteen nations are working feverishly to explore, record, and remove as much as possible before the Aswan Dam gates close and the entire human record of ancient Nubia is drowned forever beneath the Nile.

No wonder the modern archaeologist calls much of his job a salvage operation. Fortunately, he is far better armed than his predecessors. Borrowing not only from physicist and chemist but from soldier and prospector, geologist and botanist, the archaeologist is speeding his work at every step with a wide range of tools.

Shortcuts for archaeologists

The airplane, for example, has proved invaluable, not only in rapid surveying of remote desert and mountain areas but in placing familiar landscapes in new perspectives. When aerial photography was still young, an alert RAF officer noted strange circles and lines in air shots of the green fields of Hampshire. Investigation showed that these were minute variations in color, visible only from the air, that marked the walls and ditches‚ the hut sites and forts of prehistoric farmers. Plants growing over a buried wall ripen earlier than the surrounding crop and are seen from the air as a lighter line through the field. Plants growing over a buried ditch have more moisture to draw on and appear richer and darker. Such marks recorded by aerial survey have provided a remarkable inventory of human occupancy sites, from Neolithic times to the Middle Ages.

When a site has been found, much time and money can still be spent in fruitless digging. To pinpoint productive areas, archaeologists are using a variety of ingenious devices. In Turkey, facing the needle-in-a-haystack problem of locating small stone burial chambers in enormous earth mounds, scientists simply borrowed the familiar well driller’s rig. By drilling test shafts into each mound until they strike stone, an excavating team can locate the chambers without moving hundreds of tons of earth.

Italian archaeologists have gone a step further. After drilling through the stone vaults of Etruscan tombs located by surface indications, they drop a camera down the shaft and take a picture of what is inside, thus avoiding the wasted effort of digging up tombs already stripped by robbers.

More complex investigation devices make use of the fact that buried objects at a site change the electrical and magnetic environment. Resistivity surveying, a technique used by oil geologists, detects buried objects by studying ground resistance to an electric current passing between two steel probes stuck in the earth. A systematic grid of test probes across a site reveals a pattern of low or high readings that tells the expert of walls or ditches underground. High resistance indicates buried rocks — perhaps an ancient wall, a stone floor, or a tomb. Low resistance may mean a ditch that has filled with earth — the fill is damper than the undisturbed soil around it. A resistivity survey in Britain is trying to find the treasure King John lost in 1216 when an exceptionally high tide swept the royal baggage train from the causeway across the Wash Estuary, now dry land.

Magnetic location, another geologist’s technique, has been applied to archaeological prospecting with particular success by Oxford University scientists. The earth is a huge magnet, surrounded by a magnetic field, the invisible force that makes the compass needle point toward the magnetic pole. Heating of the iron oxide particles found in most soils often increases their magnetism enough to create small local variations in the strength of the magnetic field. Detection of such changes may indicate an old campfire site or cook oven buried below. Many RomanoBritish pottery kilns have been found by this means, even though their fires last burned many centuries ago.

New methods of dating

The earth’s magnetic field can also be used to determine the age of buried objects. Over the centuries, the direction of the field has constantly changed. When iron particles are magnetized by heat, the field direction is locked into the soil. When undisturbed baked clay, as in a kiln, is discovered, analysis can reveal the local direction of the earth’s magnetic field at the time the clay was last heated. Using samples of clay of known date, it is possible to prepare a chart of field variations over the centuries and relate new finds to this time scale.

University of California scientists are dating pottery or bricks by means ol thermoluminescence. Thorium and uranium, which occur in most clays, are naturally radioactive, bombarding the minerals around them with alpha particles that distort their crystal structure. If the clay is heated, these distortions are removed, but the bombardment begins again when the baked clay cools. Thus, all the crystal distortion found in the clay must have accumulated after the pot was baked and is a measure of the elapsed time since the potter placed his wet clay in the kiln. The scientist heats a fragment of clay and measures the visible light it gives out — the energy released as the distortions disappear.

Dating by means of the radioactive isotope carbon 14 is even more useful because it can be used on any object of organic origin. Continually formed in the upper atmosphere by cosmic ray bombardment of nitrogen, carbon 14 is absorbed by all living matter, plant or animal, and becomes uniformly distributed throughout the living world. When the living matter dies, the radioisotope gradually “decays” — that is, turns into other substances — at a known rate. The amount of the isotope found in an archaeological object — a charred log or a scrap of leather, for example — compared with the amount found in a comparable living specimen tells roughly how many centuries have elapsed since the tree was cut or the cow killed.

Because archaeologists have learned a great deal about the availability of different materials at various times and places in antiquity, physical analysis of the artifact often yields clues about who made it, where, and when. Using the technique of emission spectrometry, the scientist burns a tiny metal scraping or pottery chip with an electric spark leaping between two electrodes. The wavelengths of light emitted show what elements have been volatilized. Or X rays can be focused on a specimen to stimulate inner electron shells of its atoms to emit secondary X rays, whose wavelengths tell the researcher what elements are present. Still a third approach is to X-ray a powdered sample to produce a shadow pattern that reveals the crystal structure of the material, so that the minerals present can be identified.

Even the analysis of stone can yield valuable clues. British investigators were puzzled at finding Stone Age axes made of rock quite unlike any for a hundred miles around. Checking the crystalline structure of tiny slices from the axes, rock experts were able to identify their structure with rocks found in four different areas of Britain, all remote from where the axes were found. From this they determined that there were at least four “factories” where prehistoric stonesmiths made tools and weapons that were traded across Britain. In another case, analysis of the limestone used in two T’ang statues confirmed ancient Chinese traditions of their common origin, despite wide differences in style and in their outward appearance.

Processing by computer

Much archaeology is concerned with classification of everything from grave sites to bronze axes, to find the geographical and chronological relationships among the people who made them. The ubiquitous computer can do this not only far more quickly but on a much larger scale than could a crew of scientists. Dataprocessing systems can prepare statistical tables of scores of details — size, shape, material, decoration; then analyze the mass of information and report which characteristics are commonly found together.

This technique, applied by a Cambridge University archaeologist to all the remains left by a little-understood prehistoric society called the Bell Beaker Culture, has revealed how the culture developed after the beakers came to Britain from the Continent about 2000 B.C.

With this technological armament and the pressure of events, archaeological research is enjoying a boom, but not every archaeologist is happy about it. Relics are being collected faster than they can be examined, classified, and published, and some archaeologists would like to have all fieldwork suspended for a holiday of perhaps five years. There are experts who fear that their contemporaries may be repeating a mistake of the past — digging up and in effect destroying evidence that future archaeologists would be far better equipped to interpret, thanks to the continuing development of new scientific techniques.

This is a minority view, however. Most archaeologists point out that the bulldozers will not wait for the museum expert to catch up with his backlog of artifacts or to develop new techniques; the site that is left for future exploration may not be there ten years from now. And archaeologists are convinced that it is as important for man to know where he has been as to know where he is going.

Capsule pipelines

Someday we may pump wheat and iron in pipelines across the continent iust as we do oil and gas today. In fact, some pipelines may be common carriers, like railroads or shipping lines. A bold new approach to pipelining, under study by the Research Council of Alberta, Canada, opens up the possibility of sending all sorts of solids through pipes. Although the system is still in the laboratory stage, it could eventually have major impact on bulk transportation methods.

Pipeline enthusiasts will tell you that solids have been sent through pipes ever since the forty-niners sluiced their gold-bearing sands. Fertilizers, cement, and ores are being piped today. And in the last few years a hundred-mile coal-carrying pipeline proved so successful that there is talk of long lines to carry coal from Appalachian mines to the East Coast, or from Utah to the Pacific. But until now it has been possible to pipe solids only in the form of a slurry — fine particles suspended in a liquid.

Slurry pumping has high power demands, since the particles must move fast to keep from settling. Separating the liquid and the solid at the receiving end can be difficult and costly, although methods have been developed to burn coal slurry without drying it. And many materials arc not suitable for slurry pumping at all because they would be damaged by contact with the carrier.

The Alberta scientists propose to overcome these difficulties by sending solid material through the pipe as large slugs or in containers. Separation would be easy. Power requirements would be less. And commodities like wheat or chemicals could be kept separated from the liquid by being carried in disposable capsules — say, of plastic.

The researchers, whose work is supported by the Canadian government, got the idea when they observed water and oil of the same density flowing together through a horizontal pipeline. The oil formed spherical or elongated bubbles in the center of the stream which moved faster than the water around them. Their presence in a turbulent flow either had no effect on the pressure gradient or even reduced it. Suppose, the scientists speculated, those bubbles were capsules or solid slugs of iron or aluminum. Would they flow through the pipe in the same way?

To find out, the Canadian researchers built small-scale transparent plastic pipelines in the laboratory, in which they tested hollow cylinders and spheres loaded with lead shot or mercury, and solid aluminum slugs of various shapes. Their bright idea works in the laboratory. Now Canadian industry is reported interested in tests on a commercial scale.

Looking ahead, the researchers believe the capsule container would be unnecessary for some products. Preliminary indications are that coal, sulfur, and potash could be mixed with oil or water to form a paste which would be molded into ingots. Metals could be cut as slugs. Since Alberta has both coal and oil to move to market, the Research Council scientists are particularly interested in piping them together, so that everything pumped through the pipe would be payload. The coal can be suspended in oil, but carrying it in slug form would make it easier to separate it from the oil.

Estimated capital costs for the proposed pipelines appear higher than for ordinary pipelines. However, capsules offer a power advantage. Horsepower requirements for pumping high concentrations of capsules (up to 80 or 90 percent by weight of the pipe volume) can be sharply cut, as compared with slurries, since the speed of the stream does not have to be kept high to prevent settling.

Sheets of capsules

The capsule principle appears in different form in a National Lead Company material called Nalcon. The company has developed a process that wraps individual cellulose fibers in a polyethylene jacket, then forms the capsules into sheets on a papermaking machine. The result is a material that is porous, like cellulose‚ and chemically resistant, like polyethylene. Nalcon is being used for storage battery separators and industrial filter cartridges. Some other materials proposed by the company for encapsulation in sheets are asbestos, carbon black, and glass fiber.

A new kind of plastic

In recent years the trend has been to substitute synthetics made from chemicals for materials of animal or vegetable origin — nylon for silk, for example. Now scientists report a development in the other direction ■— still only a laboratory stunt, but perhaps a portent of things to come. That lowly form of life, the bacterium. has been put to work making plastic. Rhizobium, which fixes nitrogen in the root nodules of leguminous plants, has long been known to contain polyester particles that may constitute as much as 80 percent of its dry weight. Two chemists at the research center of W. R. Grace & Company have found a way of extracting the polyester to form a thermoplastic material that can be melted and molded into objects or cast into a film.

Since the new plastic has a low melting point — 178 degrees — and has no particularly outstanding characteristics, it is hardly likely to compete with the standard varieties on the American market. The Grace Company scientists point out, however, that underdeveloped countries that lack the organic chemicals needed to make commercial plastics might produce this plastic from fermentation bacteria in molasses or other equally available materials. Food-packaging films are suggested as one application.

Water bags or wineskins are still used in many parts of the world, and a fancy variety is now offered to some Americans. Milk in sixto tenquart plastic bags, said to stay fresh longer than bottled or cartoned milk, is being delivered in several cities. In the home refrigerator, the bags are kept in a special dispenser which has a lever-operated spigot at the bottom, eliminating the usual wide opening that may expose the contents to bacteria in the air. Dairies testing the Container Corporation of America innovation report their plastic-bag customers are drinking more milk per family, apparently because it is so easy to pour.