After wandering in the wilderness for 40 years, the Israelites entered the Promised Land and laid siege to the strategic city of Jericho. They circled the city once a day for six days. Then, on the seventh day, they circled it seven times.

Extensive damage to these mud-brick fortifications reveals they did, indeed, fall. And carbon dating of cereal grains suggests the city was destroyed some time after 1315 BC - coinciding with the likely date of the arrival of the Israelites from Egypt.

Plainly, however, no amount of shouting or trumpet-blowing could have caused the collapse of such a great fortress.

Some suggest an earthquake was to blame. But this would have affected the Israelites outside as well as the residents within. Nor would it explain why some parts of the walls were apparently left untouched.

To the modern mind, a far more likely explanation is that the Israelites had some powerful secret weapon - a weapon, if you like, of mass destruction.

But the technology of war was then in its infancy. How could the Israelites have summoned up a destructive power rivalled only by the bombs now raining down on Saddam Hussein? Did they have the knowledge to harness or bend -the laws of physics?

Biblical evidence offers one explanation. It suggests that the Israelites' secret weapon was the Ark of the Covenant.

This fabulous golden chest, filled with sacred relics, was carried before them when they went into battle. It is credited with ferocious powers to deal out death and destruction.

Meanwhile, modern science has its own light to shed. In Arizona, a team of chemists and technologists has filed worldwide patents for a miraculous powder produced by superheating gold.

Their findings dangle the exciting prospect of revising our preconceptions about the laws of gravity, while also unlocking phenomenal reserves of energy. Most intriguingly of all, they may help explain the secret powers of the Ark of the Covenant.

Those familiar with the cinema adventures of Indiana Jones and the film Raiders Of The Lost Ark will recall the scenes in which this fabled treasure is supposedly rediscovered and slaughters Nazi troops with mysterious death rays.

In fact, this is not simply the fantasy of Hollywood scriptwriters. Jewish and Christian literature is full of references to the Ark's ability to lay waste the enemy - not to mention unwary Israelites, too.

Once, when it was being transported by an ox-drawn cart, a man named Uzzah reached out his hand to steady it and was instantly struck dead. Two sons of Aaron, the brother of Moses, were killed by bolts of light that leapt from it.

On another occasion, an accident caused the Ark to blaze its fire into the midst of the Israelites, causing a number of deaths.

They were constantly warned to keep their distance from it, and the priests who did approach it were careful to go barefoot and wear special golden breastplates, as if to shield them from its power

But perhaps the surest sign of the Ark's potency is that the Israelites never lost when they carried it into battle; on a rare occasion when they left it at their camp, they were routed. It was the crucial factor in all their military victories.

This brings us back to the siege of Jericho. On each of the circuits of the city, the Ark was carried aloft by the Israelites. Could it be that it emitted the cataclysmic force that smashed the walls?

I believe the answer is `Yes'. And I believe the source of the Ark's astonishing powers was the same powdered gold that. has been discovered by researchers in Arizona.

As I am about to show, this powder can be used not only to destroy life but to preserve it. It was prized by the ancient Egyptians as a magical medicine, and was known to alchemists by the rather confusing title of the Philosophers' Stone, which I will explain later.

This same powder holds the key to the wonders of the pyramids, and could also open a path to other dimensions. It is, in short, one of the most remarkable substances known to creation.

Yet open any scientific textbook and you won't find a word about it. Only a small number of investigators have begun to appreciate its significance. Indeed, the whole story starts with a sensational discovery that has been shamefully ignored for almost 100 years.

In March 1904, the distinguished British archaeologist Sir W. M. Flinders Petrie stood on a wind- swept plateau in the Sinai desert.

He had come to survey the rugged outcrop that the Old Testament refers to as Mount Horeb. It was here that Moses received the Ten Commandments from God. To his astonishment, Petrie stumbled on a vast man-made cave beneath this sacred site.

Opening out from it, and buried under the sand and rock, were the remains of a huge Egyptian temple dating back to 2600 BC.

The treasures Petrie found included obelisks and pillars, statues and tables, an altar, vases, amulets and wands, They would end up scattered in museums across the world, although many were kept from public view.

This, in itself, is suggestive. Powerful figures, including Petrie's sponsors, clearly felt his discoveries posed too many questions about the holy mountain. They did their best to suppress his work.

His most remarkable finds were a metallurgist's crucible and a considerable amount of pure white powder The powder - several tons of it -had been concealed beneath carefully laid flagstones, suggesting it was of great significance.

For want of any other explanation, Petrie wondered whether it was ashes left over from animal sacrifices. But animal sacrifices were not carried out until much later in Egyptian history, and he could find no fragments of bone or any other foreign matter.

A sample was sent to the British Museum for analysis but, bizarrely, no record of it remains, And when a baffled Petrie finished his survey, he foolishly left the remaining powder exposed to the Sinai winds - which scattered every speck.

Meanwhile, hieroglyphics on the temple's walls were found to contain dozens of mentions of a mysterious substance called mfkzt - sometimes pronounced mufkuzt.

The same word had been found at other Egyptian sites, and scholars were stumped by it. All they could deduce was that it signified some form of gem, mineral or metal that was extremely valuable and regarded as in some way unstable.

Various candidates had been suggested - including turquoise, copper and malachite, a mineral used in ornaments - but, by virtue of other references in Egyptian . . texts, all were ruled out.

An intriguing possibility arose. Since Petrie's white powder and mfkzt were equally hard to identify, and yet seemingly of great importance, maybe they were one and the same.

In a series of strange scenes, gods and pharaohs were shown being offered conical loaves of what was described as `white bread', with inscriptions suggesting it had magical health-giving properties. One such carving read: `The presentation of white bread that he may be given life.'

Remarkably, there were also numerous hints that the key ingredient of the loaves was gold. Under one image of a pharaoh feeding the bread to a god, the inscription stated: `He gave the gold of reward; the mouths rejoiced.'

This was tantalising. Gold was the one precious substance that had not been eliminated as the possible meaning of the mysterious mfkzt.

Could Petrie's white powder have been a hitherto unknown form of gold, which was fed to Egyptian pharaohs in esoteric rites to give them god-like health and longevity?

If so, what other remarkable powers could the powder possess? And what lost science could produce it?

To find out, let's look more closely at the Biblical events at Mount Horeb, the site of Petrie's temple. Besides being the place where God spoke to Moses, it is also where Moses destroyed the golden calf.

The Israelites had made the calf as an idol, using melted down gold earrings. By any standards, what happened next is very strange.

According to the book of Exodus, Moses took the golden calf `and burnt it in the fire and ground it into powder, and scattered it upon the water, and made . the children of Israel drink it'.

There are three points I'd like to make about this. The first is that -burning gold by conventional means produces molten gold, not powder Something unusual is happening here.

The second point is that the whole thing sounds more like a ritual - an enriching act of communion - rather than a punishment.

And from this follows the third point. The idea of Moses mixing powdered gold with water and giving it to his followers to drink carries a striking echo of the pharaohs being fed powdered gold mixed with bread as a `life-giver'.

But how could Moses, the Egyptians or anyone else turn gold into powder? Such a mysterious process brings to mind the activities of medieval alchemists.

In popular understanding, their aim was to discover the Philosophers' Stone that would produce gold from base metal. In fact, the alchemists' writings make it clear they believed the Philosophers' Stone was itself made of gold, and that their purpose was to explore its magical properties.

In the words of one of the most celebrated experts on alchemy, the l7th-century sage Eirenaeus Philalethes: `Our Stone is nothing but gold digested to the highest degree of purity and subtle fixation.'

It was called a stone, he said, because of its `incombustible' nature. `But its appearance,' he stressed, `is that of a very fine powder'.

Here we have another fascinating connection. For the mysterious mfkzt of the Egyptian temple - that fine white powder - seemingly derived from gold - is also described in hieroglyphics as `the noble precious stone'.

Alchemists believed that the Philosophers' Stone was the key to producing `good medicines for general use' and were fascinated by its supposed ability to defy gravity and other physical laws.

As we have already seen, the Egyptians believed that bread made with mfkzt would boost the health of their leaders. And ancient texts discovered in a pyramid near modern-day Luxor refer to something called `the field of mfkzt', in which dead pharaohs would live for ever.