1. A circuit-interrupter of the gas-flow type, comprising, in combination: a. a relatively stationary tubular venting contact through which gas may exhaust; b. a relatively movable tubular venting contact cooperable with said relatively stationary venting contact to establish an arc and through which gas may also exhaust during interruption; c. primary blast-valve means disposed closely adjacent the point of contact separation; d. casing means for confining a high-pressure gas externally of said separable contacts; e. opening of said primary blast-valve means enabling an inward flow of high-pressure gas to flow from said casing means into both of said separable contacts to bring about arc interruption interiorly of said tubular venting separable contacts; f. a first contractable insulating nozzle structure supported at the relatively stationary contact and comprising a plurality of inward-biased nozzle portions disposed interiorly of an annular nozzle holder (74)a having a nozzle opening (74a); g. said first contractable insulating nozzle structure delaying application of said inward flow of gas prior to the withdrawal of said movable tubular venting contact out of said nozzle opening; h. a second contractable insulating nozzle spaced axially along the line of contact travel from said first nozzle structure and also including a plurality of inward-biased nozzle portions; i. said movable tubular venting contact passing interiorly through both said first and second contractable insulating nozzle structures during the closing operation of the interrupter to thereby expand the nozzle portions in both nozzle structures; and, j. the contraction of said nozzle portions of the nozzle structures tending to center the established arc axially for better arc interruption characteristics.