Thermometer

In a thermometer adapted to be subjected to temperatures above the normal reading temperature range thereof without adversely affecting the accuracy of the thermometer in subsequent use thereof at reading temperatures, said thermometer having a stem provided with a longitudinal capillary through-bore, means defining a reservoir chamber at an inner end of the bore, scale means on the stem for indicating reading temperatures, and indicator liquid in said chamber and expandable as an incident of subjecting of the thermometer to reading temperatures to extend outwardly through said bore to adjacent said scale for providing a reading of the temperature, the improvement comprising means defining an expansion chamber communicating with said bore outwardly of the scale means and defining an open outlet at its outer distal end having a capillary cross section precluding gravitational flow of the indicator liquid outwardly therethrough, said expansion chamber being arranged to accommodate a preselected volume of indicator liquid thermally expanded into said expansion chamber thereby to preclude loss of indicator liquid from the thermometer by thermal expansion through said outlet notwithstanding the subjecting of the thermometer to elevated temperatures substantially above said reading temperatures and permitting return of substantially all of the preselected volume of expanded indicator liquid upon lowering of the subjected temperature.