During the course of the extensive research in arc welding being conducted at Lehigh University under joint sponsorship of the A.I.E.E. and several other organizations, apparatus for experimental welding at atmospheric pressure in controlled pure gas atmospheres has been designed and constructed. Tests in argon gas reveal 3 phenomena not previously associated with the welding arc: (1) the impossibility of maintaining a stable arc in highly purified argon under ordinary conditions; (2) the absence of all crater formation under pure iron in pure argon; and (3) the absence of all observable ``pinch effect'' accompanying the detachment of the globules from the electrode wire.