his alert reaction , actually vaulting the hood of the duesy with his left arm rigid and both legs fully extended , was all the more surprising when his rescue effort was superseded by that of the stout and plucky mrs. potsdam who , arriving a step behind the sprightly valet , fished conestoga from the mountain spring fed drink by wrapping her burly arm around the anguished woman 's plentiful midsection and heaving upward .