Went with Mr. Artaud to the shops and bought some things. Fine weather. The Thermometer at night was. 15 degrees below.0. which is the degree of freezing.1 On the 20th. of December last and on the 25th. of the same month our Thermometer was at 25. below 0. and at that of the academy2 it was at 28, which is colder than it has been here since the year 1776. In 1759 it was as low as 33.
1. The calibration is that of René Antoine Ferchault de Réaumur, French physicist and naturalist. Under Réaumur’s system the temperature range between freezing and boiling was divided into eighty degrees; hence −33°R., mentioned later in the entry, would equal −42°F., or −41°C. (Hoefer, Nouv. biog. générale description begins J. C. F. Hoefer, ed., Nouvelle biographie générale depuis les temps les plus reculés jusqu’à nos jours, Paris, 1852-1866; 46 vols. description ends ; entry for 12 Aug. 1783, below; Adams Family Correspondence description begins Adams Family Correspondence, ed. L. H. Butterfield and others, Cambridge, 1963- . description ends ; 4:287).
2. The Academy of Sciences, founded by Catherine I in 1725 in accordance with a plan of Peter the Great for the promotion of literature and science (Storch, Picture of Petersburg description begins Henry Storch, Picture of Petersburg, English transl., London, 1801. description ends , p. 297–302, 313–321, 324–344).