This chapter discusses how the challenge of extending the numerical scale beyond the temperature range in which it was established was addressed. It focuses on the investigations into the freezing point of mercury, and the master potter Wedgwood’s efforts to create a thermometer that could measure temperature in his kilns. A revitalized version of Percy Bridgman’s operationalist philosophy is used to shed light on the process of extending concepts beyond the domains of phenomena in which they were originally formulated.
Keywords: temperature, numerical scale, thermometer,