Temperature changes: The conceptual realignment of a quantity term

Recently, John McCaskey (2020) has proposed that the arrival of Daniel Fahrenheit's thermometers precipitated the eighteenth-century conceptual change of temperature. I examine the usage of the temperature term in the Philosophical Transactions for this period, leading from the creation of the Fahrenheit thermometer up to the first employment of numerical temperature within the journal, in which temperature is constituted by a numerical value. I identify four strands linking thermometry and meteorology to temperature's conceptual change: the weather data network of James Jurin; the dissemination and acclaim for Fahrenheit thermometers; a resurgence in the usage of temperature in meteorological writing; and both exploratory usage and a broadening of the term's extent as it realigned to thermometry. The realignment of temperature in this period cultivated a conception of temperature whereby it could be constituted by the numerical readings of a thermometer, a sense which had not existed previously. This historical survey demonstrates that a refinement of Joseph LaPorte's (2004) precisification account for conceptual change is required for it to accommodate temperature. I suggest two modifications: a greater potential flexibility in the term's extent, permitting the abandonment of previous senses, and the possibility for tacit conceptual changes that may proceed without stipulation.