Note 161 — PART SECOND. (continued 2)

This account is taken from the Annals of Medicine for 1798, and appears in a letter from Dr. Guthrie at Petersburg to Dr. Duncan at Edinburgh. It is drawn up with such astonishing inaccuracy, that we may well be surprised how the one physician should write, and the other print it. There seems in the first place to have been a mistake of Reaumur’s thermometer for Fahrenheit’s. But even this will not rectify the account. The zero or (0) on Reaumur’s scale is the freezing point of water; on Fahrenheit’s it is the cold produced by a mixture of salt and snow, 32 degrees below the freezing point of water. The freezing point of quicksilver has been fixed at 39, 39 1/2 or 40 degrees below the cold produced by salt and snow. When the thermometer therefore fell to 40 deg. below the freezing point of water, it was only eight degrees below the cold of salt and snow, and not equal to the congelation of mercury by more than thirty degrees. The difference between this and forty-two degrees below the freezing point of quicksilver is enormous and incredible. It indicates a degree of cold hitherto unobserved on the face of the earth, and scarcely equalled by the latest experiments made at Hudson’s bay, where, by means of vitriolic acid and snow, the thermometer was made to indicate a degree of cold 40 degrees below the freezing point of quicksilver. The inaccuracy and confusion of this account, however, does not affect the subsequent part relative to Mr. Billings’s journey.