blade extremity 34 against the opposite side of slot 32 the continued differential movement of the tubular members 38 and 40 caused by their rising temperature with exposure to the flame of a burner will continue to retract inner tube 40 from chamber 18 of housing 12 this continued motion will pivot switch blade 24 about the point of engagement of contacts 22 and 26 causing the opposite lateral extremity 34 of the switch blade to move to its opposite position in slot 32 against the biase of spring 39 fig6 and 7 illustrate the different respective positions of the lateral extremity 34 within slot 32 fig6 corresponds to the position of extremity 34 in slot 32 as illustrated in fig4 while fig7 refers to this position as shown in fig5 the degree of travel of the movable contact 26 between the positions shown in fig1 and 4 is desirably fixedly adjustable this adjustment capability is provided by a adjustable stop in the form of a pin 92 having an externally threaded shank 94 which is received within a threaded aperture in insulating spacer plate 30 the operation of the thermally responsive actuator will now be described the actuator is illustrated in fig1 at its cold position with switch contacts 26 and 22 separated when the thermally responsive assembly of tubes 38 and 40 is exposed to an elevated temperature such as the pilot burner of an appliance and the like an electrical potential is generated between the cold junction ends of these tubular members the inner tubular member 40 is retracted from housing 12 by the differential thermal expansion of these tubular members the withdrawal of the tube initially moves the switch blade into.