Films of the Boys' Own genre had a satisfactory way of disposing of the villain when it was time to bring an adventure to a close. He would fall, because of his own clumsiness, into a pit of quicksand, there to struggle wildly as he was sucked slowly, but inexorably, to his fate.
Naturally, our hero would do his best to save the rascal, but he would usually fail. After the last loutish Donnerwetter! villains in those days were invariably German - the last we would see of the bearded cad was an upstretched hand, vainly gesticulating for help before it, too, finally disappeared into the quagmire.
The villain, of course, ought to have had a little manly pluck. Quicksand does not suck its victim downwards; indeed it will try to support him given half a chance. It has a density of 1.6 or thereabouts, compared to 1.0 in the case of freshwater, and 1.02 for salt water.
Were the villain to lie calmly on his back with arms outstretched, he would be supported even more effectively than if floating on the surface of the sea. The difficulty, if you go in feet first, is that quicksand has a reluctance to "let go". To extract a limb, you have to fight hard against the vacuum left behind.
The perceived evil nature of quicksand is emphasised by its very name. It derives from an archaic form of the word "quick", which meant to "be alive", or "moving", and which seems to impute an active malevolence to the sand itself.
But, in fact, just add water and any sand is quicksand.
Sand is most familiar to us in the guise in which we see it on the seashore - either dry and powdery, or hard-packed, damp and firm.
Since the grains are irregular in shape and rough, they lock together to support the weight of anything upon them. Sand becomes "quick", however, when water, often welling up from a subterranean source, surrounds the individual grains, and fills the little gaps and spaces in between; then they cannot lock together, the sand behaves like liquid, and the weight it can support is determined only by the familiar Archimedes Principle.
Quicksand is most likely to be found where there are springs, where rain, falling on relatively high ground, flows downwards through channels in the rock to surge upwards again at some lower level underneath an area of sand.
Quicksand, therefore, is rarely found on flat countryside, or where the landscape has deep ravines and gorges into which water drains. It is a phenomenon of a moderately hilly landscape of the kind where springs are common.
