appearance ... work - their form and the material of their work.
beryl - rather, “the glancing appearance of the Tarshish stone”; the chrysolite or topaz, brought from Tarshish or Tartessus in Spain. It was one of the gems in the breastplate of the high priest (Exo 28:20; Son 5:14; Dan 10:6).
four had one likeness - The similarity of the wheels to one another implies that there is no inequality in all God’s works, that all have a beautiful analogy and proportion.