What is "incondensible gases"

Permanent \Per"ma*nent\, a. [L. permanens, -entis, p. pr. of permanere to stay or remain to the end, to last; per + manere to remain: cf. F. permanent. See Per-, and Mansion.] Continuing in the same state, or without any change that destroys form or character; remaining unaltered or unremoved; abiding; durable; fixed; stable; lasting; as, a permanent impression.

Eternity stands permanent and fixed.
--Dryden.

Permanent gases (Chem. & Physics), hydrogen, oxygen, nitrogen, and carbon monoxide; -- also called incondensible gases or incoercible gases, before their liquefaction in 1877. The term is now archaic.

Permanent way, the roadbed and superstructure of a finished railway; -- so called in distinction from the contractor's temporary way.

Permanent white (Chem.), barium sulphate ( heavy spar), used as a white pigment or paint, in distinction from white lead, which tarnishes and darkens from the formation of the sulphide.

Syn: Lasting; durable; constant. See Lasting.