hese early machines probably employed some form of foot
treadle but even these could not turn the wheel very fast. If the
stone had a large enough diameter, it was possible to get the speed at
the outer edge high enough to produce sparks when grinding hard
material. The "work" took place at some distance from the axis,
usually at the edge of the stone.

The wheel we usually associate with ancient times is the cart wheel.
In its earliest form it was a solid wheel, like those still in use in
primitive sections of Mexico. Even with the cart wheel, ancient man
would associate the edge of the wheel with the "work" of the wheel.
This was the part that left a track in the mud and dust, crushed an
occasional rock and fractured an occasional toe.

In order to increase the efficiency of military chariots it was
necessary to build a wheel that was lighter, yet just as strong as the
solid model. This was first done by cutting out "lightening holes"
between the hub and rim. Pressing this invention to the ultimate
produced a spoked wheel. The Egyptians used a six-spoked chariot wheel
thousands of years before Ezekiel's time, and the Greeks and others
had four-spoke models. This was quite an invention and in addition to
its useful aspects, it produced some rather unusual, even magical
side-effects. As every child knows, if you turn your tricycle
upside-down and spin the wheel, the spokes seem to vanish. All that
can be seen is the rim and the parts of the hub near the center of
rotation. No matter what shape the hub actually is, it too looks round
like a wheel. It is very likely that such an effect was referred to as
"a wheel within a wheel."

In verse 16 Ezekiel says that, "wheels and their work was the colour
of beryl ...", a blue-green color. This sounds like the emphasis is on
the color at the _edge_ of the wheel. This could be from a flame
coming from jets on the tips of the rotors.

All of the creatures must have started their rotors. ("... they four
had one likeness.") They looked like "... a wheel in the middle of a
wheel." Or the spinning spokes of a wheel. Notice also that he never
mentions "wings" and "wheels" at the same time, for when one appears
the other vanishes.

_17. When they went, they went upon their four sides: and they turned
not when they went._

If four men were standing fairly close together on the ground with
running helicopters, they would tend to spread out as they left the
ground, so as to not r