“The appearance of the wheels and their work was like unto the colour of a beryl: and they four had one likeness: and their appearance and their work was as it were a wheel in the middle of a wheel.”
King James Version (KJV)
1:16 Work - All that was wrought, whether engraved or otherwise was of one colour. Beryl - A sea green. One likeness - The same for dimensions, colour, frame, and motion. In the middle - It is probable, the wheels were framed so as to be an exact sphere, which is easily rolled to any side.