Abstract: A rod and tube thermosensing device adapted for high temperature use has a first rod member comprising a rod of refractory metal having a metal cladding thereon which protects the refractory metal against excessive oxidation and which cooperates with the rod of refractory metal in providing the first member with a relatively low effective coefficient of thermal expansion. This first rod member is coaxially disposed in a tube of a metal of relatively higher coefficient of thermal expansion and has one end of the rod member secured to a corresponding end of the tube, whereby the opposite ends of the first rod member and tube are free to move relative to each as an indication of the temperature to which the device is subjected.