move downwardly therein creating fluid chamber 49 in the housing 28 in the direction of arrow g and compresses the gas in the chamber 21 the pressure exerted on the on the gas in the chamber 21 also causes the secondary piston 36 to move downwardly in the direction of arrow h into contact with the end piece 38 because pressure substantially in excess of hydrostatic well pressure is required for setting the tool 10 after the tool 10 is set if the zone in the vicinity of the tool 10 experiences a drop in temperature the fluid in the tool 10 will contract when this condition occurs as shown in fig5 the compressed gas in the chamber 21 causes the floating piston 36 to move upwardly in the direction of arrow i which in turn operates to maintain a substantially uniform fluid pressure in tool 10 and prevent the anchor and seal from being compromised the secondary piston 36 remains in contact with the end piece the inflation fluid in chambers 24 and 49 will expand in the event of an increase of temperature in the vicinity of the tool 10 any expansion of fluid within the tool 10 is immediately transmitted through the passageway 30 to the piston 32 causing the piston 32 to move downwardly in the direction of arrow j as shown in.