What is another word for "ether"?

Roget's Thesaurus (1911) lists these synonyms for "ether": absence, aeration, aerial, aerification, aeriform, aerodynamics, aerostatics, agent, air, airy, alkali, ammonia, ammoniacal, anaesthesia, anaesthetic, anaesthetize, astatic, balloon, barm, benumb, bladder, blunt, bubble, buoy, buoyancy, buoyant, callous, case, cavernous, chloral, chloroform, cloud, cobweb, coma, comatose, compressibility, compressible, convection, cork, dead.