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 run into each other. Moreover, with a helicopter, it is not necessary to _face_ the direction you intend to go. This sounds like four men lifting off the ground, spreading out slightly and starting up and away, in formation. _18. As for their rings, they were so high that they were dreadful; and their rings were full of eyes round about them four._